CN110015170B

CN110015170B - Battery equalization method, system, vehicle, storage medium and electronic device

Info

Publication number: CN110015170B
Application number: CN201710775023.3A
Authority: CN
Inventors: 罗红斌; 王超; 沈晓峰; 曾求勇; 刘苑红; 张祥
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2017-08-31
Filing date: 2017-08-31
Publication date: 2022-10-18
Anticipated expiration: 2037-08-31
Also published as: CN110015170A; WO2019042410A1

Abstract

The present disclosure relates to a battery equalization method, a system, a vehicle, a storage medium, and an electronic device, the method comprising: acquiring the SOC value of at least one single battery in the battery pack; determining a section where the SOC value of at least one single battery is located according to the SOC value of at least one single battery in the battery pack and three sections of (0, SOC1), (SOC 1, SOC 2) and (SOC 2, 100%); and determining the single battery needing to be balanced by adopting the SOC difference value or the load voltage difference value according to the interval where the SOC value of the at least one single battery is located. By adopting the method, aiming at the three conditions that the SOC value of at least one single battery in the battery pack is at (0, SOC1), or at (SOC 1, SOC 2) or at (SOC 2, 100%), in each condition, the single battery needing to be balanced is determined by utilizing the battery parameter information with higher accuracy, so that the accuracy of determining the single battery needing to be balanced is improved.

Description

Battery equalization method, system, vehicle, storage medium and electronic device

Technical Field

The present disclosure relates to the field of control technologies, and in particular, to a battery equalization method, a battery equalization system, a vehicle, a storage medium, and an electronic device.

Background

A large-capacity battery that provides power energy for an electric vehicle is often referred to as a power battery. The vehicle power battery generally comprises a module formed by connecting a plurality of single batteries in series. With the use of batteries, the difference between the single batteries is gradually enlarged, the consistency between the single batteries is poor, the capacity of the battery pack is limited due to the short plate effect of the batteries, the capacity of the battery pack cannot be fully exerted, and the whole capacity of the battery pack is reduced. On the other hand, the gradual expansion of the differences between the single batteries may result in some single batteries being overcharged, some single batteries being overdischarged, which may affect the battery life and damage the batteries, and may also generate a large amount of heat to cause the batteries to burn or explode.

Therefore, the method has very important significance for effectively and uniformly managing the power batteries of the electric automobile, being beneficial to improving the consistency of the batteries in the battery pack, reducing the capacity loss of the batteries, and prolonging the service life of the batteries and the driving range of the electric automobile.

At present, when balancing management is performed on a power battery pack, a single battery needing to be balanced needs to be determined from the power battery pack, so that battery information of each single battery in the power battery pack needs to be acquired in real time, and then, which single batteries need to be balanced is determined according to the battery information, and further, the single batteries needing to be balanced are balanced. Since the battery information of the single battery includes a plurality of types, such as a load voltage value, an SOC value, etc., and the accuracy of different types of battery information is different under different conditions, how to utilize the battery information of the single battery to improve the accuracy of determining the single battery to be balanced is a problem to be solved.

Disclosure of Invention

The purpose of the present disclosure is to provide a battery equalization method, system, vehicle, storage medium, and electronic device to optimize a battery equalization process.

In order to achieve the above object, a first aspect of the present disclosure provides a battery equalization method, including:

acquiring the SOC value of at least one single battery in the battery pack;

determining a section in which the SOC value of at least one single battery is located according to the SOC value of at least one single battery in the battery pack and three sections of (0, SOC1), (SOC 1, SOC 2) and (SOC 2, 100%);

and determining the single battery needing to be balanced by adopting the SOC difference value or the load voltage difference value according to the interval where the SOC value of the at least one single battery is located.

Optionally, the method further comprises:

and determining the value of SOC1 and the value of SOC2 according to the corresponding relation between the open-circuit voltage OCV and the SOC of the single battery.

Alternatively, the correspondence relationship between OCV and SOC satisfies: the rate of change of the OCVs with the SOCs in the sections (SOC 1, SOC 2) is less than a prescribed value, and the rate of change in the sections (0, SOC1) and (SOC 2, 100%) is greater than or equal to the prescribed value.

Optionally, the determining, according to an interval where the SOC value of at least one battery cell in the battery pack is located, to use the SOC difference value or the load voltage difference value to determine the battery cell that needs to be balanced includes:

when the number of the single batteries belonging to the interval (0, SOC1) in the SOC values of the single batteries in the battery pack is greater than or equal to a first preset value, determining to adopt a load voltage difference value to determine the single batteries needing to be balanced;

when the number of SOC values belonging to intervals (SOC 1 and SOC 2) in the SOC values of each single battery in the battery pack is larger than or equal to a second preset value, determining to adopt an SOC difference value to determine the single battery needing to be balanced;

and when the number of the SOC values belonging to the interval (SOC 2, 100%) in the SOC values of the single batteries in the battery pack is greater than or equal to a third preset value, determining the single batteries needing to be balanced by adopting the load voltage difference.

determining a reference SOC value required by balancing according to the SOC value of at least one single battery in the battery pack;

when the reference SOC value belongs to an interval (SOC 1, SOC 2), determining to adopt an SOC difference value to determine the single battery needing to be balanced; otherwise, determining to adopt the load voltage difference value to determine the single battery needing to be balanced.

Optionally, the determining a reference SOC value required for balancing according to the SOC value of at least one battery cell in the battery pack includes:

and determining the SOC value of any single battery in the battery pack as the reference SOC value.

Optionally, the specified value is a sampling precision of the voltage.

Optionally, when it is determined that the SOC difference value is adopted to determine the unit cells requiring equalization, the method further includes:

acquiring a reference SOC value required by balancing;

determining an SOC difference value between the SOC value of the at least one single battery and a reference SOC value required by equalization, wherein the reference SOC value required by equalization is determined according to the SOC values of the single batteries in the battery pack;

and determining the single battery needing to be balanced as the single battery with the SOC difference value larger than or equal to the first balance starting threshold value in the at least one single battery according to the SOC difference value and the first balance starting threshold value.

Optionally, the reference SOC value is a minimum value among SOC values of the individual batteries in the battery pack;

the determining of the SOC difference value between the SOC value of the at least one battery cell and the reference SOC value required for equalization includes:

determining an SOC difference value between the SOC values of the following single batteries and a reference SOC value required for balancing:

the single battery with the maximum SOC value in the battery pack; or

And the other single batteries except the single battery with the SOC value of the minimum value in the battery pack.

Optionally, after determining that the single battery needing to be balanced is the single battery with the SOC difference value greater than or equal to the first balancing start threshold value in the at least one single battery, the method further includes:

and controlling the discharge of the single battery of which the SOC difference value is greater than or equal to the first balance starting threshold value in the at least one single battery.

Optionally, the reference SOC value is a maximum value among SOC values of the individual batteries in the battery pack;

the determining of the SOC difference between the SOC value of the at least one battery cell and the reference SOC value required for equalization includes:

the single battery with the minimum SOC value in the battery pack; or

And the other single batteries except the single battery with the SOC value of the maximum value in the battery pack.

and controlling the charging of the single battery with the SOC difference value larger than or equal to the first equalization starting threshold value in the at least one single battery.

Optionally, the reference SOC value is an average value of SOC values of the individual battery cells in the battery pack;

and determining the SOC difference value between the SOC value of each single battery in the battery pack and the reference SOC value.

Optionally, after it is determined that the cell requiring equalization is the cell of which the SOC difference value is greater than or equal to the first equalization start threshold value in the at least one cell, the method further includes:

and for any single battery of which the SOC difference value is greater than or equal to the first equalization starting threshold value in the at least one single battery, controlling the single battery to discharge when the SOC value of the single battery is greater than the reference SOC value, and controlling the single battery to charge when the SOC value of the single battery is less than the reference SOC value.

for any single battery of which the SOC difference value is greater than or equal to the first equalization starting threshold value in the at least one single battery, determining a target equalization duration of the single battery according to the SOC value of the single battery and the reference SOC value;

and controlling the balancing of the single battery according to the target balancing duration of the single battery.

Optionally, when it is determined that the load voltage difference is adopted to determine the single battery needing balancing, the method further includes:

determining a reference load voltage value required for balancing according to the load voltage value of each single battery in the battery pack;

determining a load voltage difference value between a load voltage value of the at least one battery cell and the reference load voltage value;

and determining the single battery needing to be balanced as the single battery with the load voltage difference value larger than or equal to the second balance starting threshold value in the at least one single battery according to the load voltage difference value and the second balance starting threshold value.

Optionally, the reference load voltage value is a minimum value among load voltage values of the individual batteries in the battery pack;

the determining a load voltage difference value between the load voltage value of the at least one battery cell and the reference load voltage value comprises:

determining a load voltage difference value between the load voltage value of the following unit cells and the reference load voltage value:

the single battery with the largest load voltage value in the battery pack; or

And the other single batteries except the single battery with the load voltage value of the minimum value in the battery pack.

Optionally, after it is determined that the cell requiring balancing is the cell in which the load voltage difference value in the at least one cell is greater than or equal to the second balancing start threshold, the method further includes:

and controlling the discharge of the single battery with the load voltage difference value greater than or equal to the second balance starting threshold value in the at least one single battery.

Optionally, the reference load voltage value is a maximum value among load voltage values of the individual batteries in the battery pack;

the single battery with the minimum load voltage value in the battery pack; or

And the other single batteries except the single battery with the load voltage value of the maximum value in the battery pack.

and controlling the charging of the single battery with the load voltage difference value greater than or equal to the second balance starting threshold value in the at least one single battery.

Optionally, the reference load voltage value is an average value of load voltage values of the individual batteries in the battery pack;

and determining a load voltage difference value between the load voltage value of each single battery in the battery pack and the reference load voltage value.

Optionally, after determining that the cell needing to be balanced is the cell whose load voltage difference value in the at least one cell is greater than or equal to the second balancing start threshold, the method further includes:

and for any single battery of which the load voltage difference value is greater than or equal to the second balance starting threshold value in the at least one single battery, controlling the single battery to discharge when the load voltage value of the single battery is greater than the reference load voltage difference value, and controlling the single battery to charge when the load voltage value of the single battery is less than the reference load voltage difference value.

for any single battery of which the load voltage difference value is greater than or equal to the second balancing start threshold value in the at least one single battery, determining the target balancing duration of the single battery according to the load voltage value of the single battery and the reference load voltage value;

Optionally, the method of calculating the SOC value comprises a first calculation mode corresponding to the interval (0, soc1) and the interval (SOC 2, 100%) and a second calculation mode corresponding to the interval (SOC 1, SOC 2);

the acquiring of the SOC value of each single battery in the battery pack comprises the following steps:

for any single battery in the battery pack, determining the SOC value of the single battery according to the first calculation mode;

and when the SOC value determined according to the first calculation mode belongs to the intervals (SOC 1 and SOC 2), re-determining the SOC value of the single battery according to the second calculation mode.

Optionally, the first calculation manner is a manner adopted by the single battery to calculate the SOC value last time.

Optionally, the first calculation manner is an ampere-hour integral method or an ampere-hour integral combined voltage correction method, and the second calculation manner is a different calculation manner from the first calculation manner in the ampere-hour integral method and the ampere-hour integral combined voltage correction method.

A second aspect of the present disclosure provides a battery equalization system, including:

a balancing module, an acquisition module and a control module,

the acquisition module is used for acquiring the SOC value of at least one single battery in the battery pack;

the control module is used for determining an interval where the SOC value of at least one single battery is located according to the SOC value of at least one single battery in the battery pack and three intervals of (0, SOC1), (SOC 1, SOC 2) and (SOC 2, 100%), and determining the single battery needing to be balanced by adopting an SOC difference value or a load voltage difference value according to the interval where the SOC value of at least one single battery is located;

the balancing module is used for balancing the single batteries needing balancing.

Optionally, the control module is configured to:

Alternatively, the correspondence relationship between OCV and SOC satisfies: the rate of change of OCV with SOC in the sections (SOC 1, SOC 2) is less than a specified value, and the rate of change in the sections (0, SOC1) and (SOC 2, 100%) is greater than or equal to the specified value.

Optionally, the control module is configured to:

when the reference SOC value belongs to an interval (SOC 1, SOC 2), determining to adopt an SOC difference value to determine the single battery needing to be balanced; otherwise, determining to adopt the load voltage difference to determine the single battery needing to be balanced.

Optionally, the reference SOC value is a minimum value, a maximum value, or an average value of SOC values of the individual battery cells in the battery pack.

Optionally, the specified value is a sampling precision of the voltage.

Optionally, the control module is configured to:

acquiring a reference SOC value required by balancing;

Optionally, the control module is configured to:

for any single battery of which the SOC difference value is greater than or equal to the first equalization starting threshold value in the at least one single battery, determining the target equalization duration of the single battery according to the SOC value of the single battery and the reference SOC value;

the equalization module is configured to:

and balancing the single battery according to the target balancing duration of the single battery.

Optionally, the control module is configured to:

Optionally, the reference load voltage value is a minimum value, a maximum value or an average value among load voltage values of the individual battery cells in the battery pack.

Optionally, the control module is configured to:

for any single battery of which the load voltage difference value is greater than or equal to the second balancing start threshold value in the at least one single battery, determining the target balancing time length of the single battery according to the load voltage value of the single battery and the reference load voltage value;

the equalization module is configured to:

and controlling the balance of the single battery according to the target balance duration of the single battery.

the acquisition module is used for:

and when the SOC value determined according to the first calculation mode belongs to the interval (SOC 1, SOC 2), re-determining the SOC value of the single battery according to the second calculation mode.

Optionally, the control module is connected with the acquisition module and the equalization module corresponding to the same single battery through a channel, and the control module is used for controlling the control module to be connected with the corresponding sampling module when it is determined that the single battery connected with the control module does not need equalization; or,

the control module is further used for multiplexing the channels in a time-sharing manner by the acquisition module and the balancing module when the single battery connected with the control module needs to be balanced.

Optionally, the control module includes a control chip, and the control chip is connected to the acquisition module and the equalization module corresponding to the same single battery through one pin and the one channel.

Optionally, the control module is connected to the acquisition module and the equalization module corresponding to the same single battery through two channels.

Optionally, the control module includes a control chip, the control chip is connected to the acquisition module and the equalization module corresponding to the same single battery through two pins, and the two pins correspond to the two channels one to one.

A third aspect of the present disclosure provides a computer readable storage medium having stored thereon computer program instructions which, when executed by a processor, implement the method of the first aspect of the present disclosure.

A fourth aspect of the present disclosure provides an electronic device, comprising:

a computer-readable storage medium according to a third aspect of the disclosure; and

one or more processors to execute the program in the computer-readable storage medium.

A fifth aspect of the present disclosure provides a vehicle including: a battery pack and a battery equalization system according to a second aspect of the present disclosure.

According to the technical scheme, the single batteries needing to be balanced are determined by adopting the SOC difference value or the load voltage difference value according to which of three intervals, namely the interval (0, SOC1), (SOC 1, SOC 2) and (SOC 2, 100%), the single batteries needing to be balanced are determined, and for the three conditions that the SOC value of at least one single battery in the battery pack is in (0, SOC1), or in (SOC 1, SOC 2) or in (SOC 2, 100%), battery parameter information with high accuracy is used for determining the single batteries needing to be balanced in each condition, so that the accuracy of determining the single batteries needing to be balanced is improved.

Additional features and advantages of the disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:

fig. 1 is a schematic diagram of a battery equalization system according to an embodiment of the present disclosure;

fig. 2 is a schematic diagram of a battery equalization system in which two single batteries share one equalization module according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram of a battery equalization system of another embodiment of the present disclosure;

fig. 4 is a schematic diagram of a battery equalization system in which two single batteries share one equalization module according to another embodiment of the present disclosure;

fig. 5 is a schematic flow chart of a battery equalization method according to an embodiment of the present disclosure;

fig. 6 is an open circuit voltage OCV-remaining capacity SOC curve of a unit battery according to an embodiment of the present disclosure;

FIG. 7 is a schematic diagram of a battery internal resistance model according to an embodiment of the disclosure;

fig. 8 is a schematic diagram of an equalization module according to an embodiment of the present disclosure.

Detailed Description

The following detailed description of the embodiments of the disclosure refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.

Referring to fig. 1, a schematic diagram of a battery equalization system according to an embodiment of the present disclosure is shown. This battery equalizing system includes: the system comprises a control module 101, an acquisition module 102, an equalization module 103 and a battery pack 104.

In one embodiment, each single battery corresponds to one acquisition module 102 and one equalization module 103. The acquisition module 102 and the equalization module 103 corresponding to the same single battery are respectively connected with the control module 101 through different control channels. The control module can comprise a control chip, the control chip is respectively connected with the acquisition module and the balance module corresponding to the same single battery through two pins, and the two pins correspond to the two channels one by one.

In this embodiment, the control module 101 controls the acquisition module 102 and the equalization module 103 to conduct in a time-sharing manner according to a unit cycle, and respectively performs acquisition of battery information and equalization of a battery, so that the acquisition of the battery information and the equalization are performed in a time-sharing manner. The influence of the equalizing current on the accuracy of battery information acquisition is avoided when the battery information acquisition and the equalization are simultaneously carried out.

In one embodiment, referring to fig. 1, each of the cells is connected to an acquisition module 102 and an equalization module 103, respectively. If the battery pack includes N single batteries, the number of the acquisition modules 102 is N, and the number of the equalization modules 103 is N, so that the control module 101 is connected to the N acquisition modules and the N equalization modules through 2 × N control channels, respectively.

In other embodiments, different single cells may share an equalization module, for example, N single cells in a battery pack, the same equalization module may be shared, or one equalization module may be shared for each predetermined number (for example, 2, 3, or 5, etc.) of single cells, and the like. When at least two single batteries in the multiple single batteries sharing one balancing module need to be balanced, the balancing module is alternately connected with each single battery in the at least two single batteries needing to be balanced in the balancing time interval of the unit cycle.

Referring to fig. 2, two single batteries share one balancing module, and when two single batteries sharing one balancing module need to be balanced, the balancing module is alternately connected with each single battery in a balancing period of a unit cycle. The alternate connection may be a connection that alternates according to a certain period. For example, referring to fig. 2, when the parallel switch 150 on the parallel branch 15 corresponding to one of the two single batteries 111 is closed for 2s under the control of the control module 14, the parallel switch 150 on the parallel branch 15 corresponding to the other of the two single batteries 111 is opened for 2s under the control of the control module 14. That is, the parallel switch 150 on the parallel branch 15 corresponding to each single battery 111 of the two single batteries is switched from the closed state to the open state or from the open state to the closed state every two seconds within the equalization period. Therefore, on the basis of time-sharing conduction of the acquisition module and the equalization module, the single batteries sharing the same equalization module are alternately connected with the shared equalization module during the equalization time period, and equalization is realized.

Fig. 3 is a schematic structural diagram of a battery equalization system according to another embodiment of the present disclosure.

This battery equalizing system includes: a control module 301, an acquisition module 302, an equalization module 303, and a battery pack 304. The battery pack 304 includes a plurality of unit cells connected in series. The control module 301 is connected to the acquisition module 302 and the equalization module 303 corresponding to the same cell via a control channel 305. The control module is used for controlling the connection of the control module and the corresponding sampling module when the single battery connected with the control module is determined not to need balancing; or, the control module is further configured to time-division multiplex the channels 305 according to a unit cycle by the acquisition module and the equalization module when it is determined that the single battery connected to the control module needs to be equalized.

One unit period includes: an acquisition period and an equalization period. The control module 301 controls the acquisition module 302 to sample the battery information of the single battery in an acquisition time period to obtain the battery information of the single battery. The battery information includes at least one of: voltage, current, temperature, etc. In one embodiment, the battery information may include only the voltage value, and thus, the voltage performance parameter of the unit battery may be obtained. In another embodiment, the battery information may also include a voltage value, a current value, a temperature value, and the like, so as to obtain performance parameters such as SOC, internal resistance, self-discharge rate, and the like of the single battery.

The control module 301 determines the single battery to be balanced, which needs to be balanced, according to the battery information of the single battery acquired by the acquisition module 302. For the single battery to be equalized which needs to be started, the control module 301 controls the equalization module corresponding to the single battery to be equalized, and equalizes the single battery to be equalized within an equalization time period.

Therefore, in the embodiment of the disclosure, the acquisition module and the balancing module share the same control channel, the control module controls the acquisition module and the balancing module, and the control channel is multiplexed in time according to a unit period, so that the influence of balancing current on the accuracy of battery information acquisition is avoided when the battery information acquisition and the balancing are performed simultaneously; on the other hand, compared with the embodiment shown in fig. 1, the requirement on the number of channels of the control module chip is reduced, and the hardware cost can be saved.

In one embodiment, a switch K is disposed in a control channel shared by the acquisition module and the equalization module, and the control module 301 is connected to the switch K and is connected to the acquisition module 302 or the equalization module 303 in a time-sharing manner by controlling the switch K. When the switch K is connected to the acquisition module 302, the control module 301 controls the acquisition module 302 to acquire battery information of the single battery in an acquisition cycle; when the switch K is connected to the balancing module 303, the control module 301 controls the balancing module 303 to balance the corresponding single battery.

In one embodiment, referring to fig. 1, each cell of the battery is connected to an acquisition module 302 and an equalization module 303, respectively. If the battery pack includes N single batteries, the number of the acquisition modules 302 is N, and the number of the equalization modules 303 is N, so that the control module 301 is connected to the acquisition modules and the equalization modules through N control channels.

Referring to fig. 4, an exemplary schematic diagram of two unit cells sharing one balancing module is shown. When two single batteries sharing one balancing module need to be balanced, the balancing module is alternately connected with each single battery in the balancing time interval of the unit cycle. The alternate connection may be a connection that alternates according to a certain period. Therefore, on the basis of time-sharing conduction of the acquisition module and the equalization module, the single batteries sharing the same equalization module are alternately connected with the shared equalization module during the equalization time period, and equalization is realized.

In one embodiment, the collecting module may be a voltage collecting chip for collecting the voltage of the single battery during the collecting period.

Referring to fig. 5, based on the battery balancing system shown in any one of the embodiments of fig. 1, fig. 2, fig. 3, or fig. 4, the battery balancing method according to an embodiment of the present disclosure includes:

in step S51, the SOC value of at least one unit cell in the battery pack is acquired.

In step S52, a section in which the SOC value of at least one unit battery in the battery pack is located is determined according to the SOC value of the at least one unit battery and three sections of (0, soc1), (SOC 1, SOC 2), and (SOC 2, 100%).

In step S53, determining to use the SOC difference or the load voltage difference to determine the single battery to be balanced according to the interval where the SOC value of the at least one single battery is located.

First, step S51 will be explained.

In one embodiment, the method of calculating the SOC value comprises a first calculation mode corresponding to the interval (0, soc1) and the interval (SOC 2, 100%) and a second calculation mode corresponding to the interval (SOC 1, SOC 2);

accordingly, step S51 includes:

The ampere-hour integration method is to integrate the acquired current value of the single battery with time to obtain the SOC value of the single battery; the ampere-hour integration combined voltage correction method is characterized in that firstly, an ampere-hour integration method is adopted to calculate the SOC value of a single battery, then the calculated SOC value is corrected by using the load voltage value of the single battery, and the corrected SOC value is used as the final SOC value of the single battery.

The embodiment of the present disclosure considers that there is an OCV plateau on the OCV-SOC curve of the unit cell, and in the OCV plateau, the variation amplitude of the OCV value is small, and exemplarily, fig. 6 is a schematic diagram of the OCV-SOC curve of the unit cell. As shown in fig. 6, in the [ SOC1, SOC2] section, the magnitude of variation in OCV values of the unit cells is small. Therefore, the SOC value of the battery cell cannot be accurately calculated by using the OCV value in the OCV plateau, and the battery cell requiring equalization cannot be accurately determined.

The OCV value is an open circuit voltage value of the unit cell, and is different from a load voltage value. Referring to fig. 7 and equation (1), when the battery pack is in a discharging state or a charging state, the single battery is equivalent to an ideal voltage source and is connected in series with a resistor R by using a battery internal resistance model. Then, for a single battery, the sampled voltage value V of the single battery can be obtained according to the formula (1) _L (i.e., load voltage value) to open circuit voltage value:

OCV＝V _L +I×R (1)

wherein, V _L The load voltage value collected by the collecting module in the collecting time period; i is the discharging current or the charging current collected by the collecting module in the collecting time period; and R is the internal resistance value of the single battery.

Or, in another embodiment, the voltage itself collected at the moment when the single battery to be equalized stops working and reaches a stable state, or the battery just starts working is an open-circuit voltage or can be approximately regarded as an open-circuit voltage, so that the OCV value of the single battery to be equalized can be directly collected in this case.

Alternatively, in another embodiment, the voltage collected at the moment when the battery to be referenced stops operating and reaches a steady state, or the battery just starts operating is itself an open circuit voltage or can be approximately regarded as an open circuit voltage, so the OCV value of the reference battery can be directly collected in this case.

The internal resistance value of the unit cell may be preset. Or the internal resistance value of the unit cell may be determined according to the voltage and capacity of the unit cell. For example, the internal resistance value of the unit cell is determined according to the correspondence relationship of the voltage, the capacity, and the internal resistance value of the unit cell. It should be understood that other battery models may also be employed, such as: the Thevenin model, PNGV (Partnership for a New Generation of Vehicles) model and the like realize the conversion of the collected load voltage of the single battery into the open-circuit voltage.

Therefore, the load voltage value is collected, and the following relationship exists between the load voltage value and the OCV value:

OCV value = load voltage value + internal battery resistance + battery charging current or discharging current

In general, the internal resistance of the battery and the charging current or the discharging current of the battery are constant, and therefore, the difference between the OCV value and the load voltage value is also constant, and when the magnitude of the change in the OCV value is small, the magnitude of the change in the load voltage value is also small.

In order to accurately calculate the SOC value of the single battery, the SOC value is calculated by adopting the ampere-hour integration combined voltage correction method instead of the ampere-hour integration method in the OCV plateau period, so that the problem that the calculated SOC value is inaccurate due to the fact that the SOC value is calculated by adopting the ampere-hour integration combined voltage correction method in the OCV plateau period is solved.

The present disclosure also considers that the magnitude of change in the OCV value is large in the non-OCV plateau period, and for example, as shown in fig. 6, the magnitude of change in the OCV value of the unit cell is large in the [0, soc1] and [ SOC2, 100% ]intervals. Therefore, in the non-OCV plateau period, the ampere-hour integration combined with the voltage correction method is used for calculating more accurately, and therefore the method for calculating the SOC value of the single battery in the non-OCV plateau period is provided.

According to the OCV-SOC curve of the single battery, the value range of the SOC value of the single battery is divided into three intervals: a first section, a second section, and a third section, where the second section is an SOC section corresponding to the OCV plateau section, for example, an [ SOC1, SOC2] section in fig. 6; the first and third intervals are SOC intervals corresponding to the non-OCV plateau periods, such as [0, soc1] interval and [ SOC2, 100% ] in fig. 6. The embodiment of the disclosure provides that an ampere-hour integration method is adopted to calculate the SOC value of a single battery in an SOC interval corresponding to an OCV platform period, and an ampere-hour integration combined voltage correction method is adopted to calculate the SOC value of the single battery in an SOC interval corresponding to a non-OCV platform period. The OCV is an Open Circuit Voltage (Open Circuit Voltage), and the SOC is a State of Charge (Charge).

In the embodiment of the present disclosure, since the voltage change rate is large in the first interval and the third interval, the SOC value of the battery may be calculated by performing correction by using an ampere-hour integration method and combining the real-time voltage (load voltage at this time) of the battery. In the second interval, the accuracy of the introduced voltage quantity calculation SOC value is not high due to the small battery voltage change rate, so that the SOC value can be directly calculated by adopting an ampere-hour integration method. By the mode, how to acquire the SOC value of the single battery can be further determined according to different SOC value intervals of the single battery, so that the acquired SOC value of the single battery is accurate, and the determined single battery needing to be balanced is accurate.

In another embodiment, at the moment when the battery just works, the SOC value of the battery can be calculated by using an open-circuit voltage method, that is, the voltage value of the battery (equivalent to the open-circuit voltage value at this time) is collected, and the SOC value of the battery can be calculated by looking up the OCV-SOC correspondence relationship.

For any single battery in the battery pack, firstly, calculating the SOC value of the single battery by adopting any one of an ampere-hour integral method and an ampere-hour integral combined voltage correction method, wherein the calculation mode adopted at the moment is a first calculation mode. Then judging whether the calculated SOC value belongs to an SOC interval corresponding to an OCV platform period or not, if not, indicating that the calculated SOC value belongs to an SOC interval corresponding to a non-OCV platform period, and if so, recalculating the SOC value of the single battery according to a ampere-hour integration and voltage correction method, and optionally, in this case, if the SOC value of the single battery is recalculated, using the ampere-hour integration and voltage correction method as a first calculation mode; if the calculated SOC value belongs to the SOC interval corresponding to the OCV plateau, it indicates that the calculated SOC value is accurate, and it is not necessary to recalculate the SOC value of the battery cell.

Or, judging whether the calculated SOC value belongs to an SOC interval corresponding to a non-OCV plateau, and if the calculated SOC value does not belong to an SOC interval corresponding to a non-OCV plateau, indicating that the calculated SOC value belongs to an SOC interval corresponding to an OCV plateau, since the ampere-hour integration method is more accurate than the ampere-hour integration combined with the voltage correction method in the SOC interval corresponding to the OCV plateau, the SOC value of the cell is recalculated according to the ampere-hour integration method, optionally, in this case, if the SOC value of the cell is recalculated, the ampere-hour integration method may be used as the first calculation method; if the calculated SOC value belongs to the SOC interval corresponding to the non-OCV plateau, it indicates that the calculated SOC value is accurate, and it is not necessary to recalculate the SOC value of the battery cell.

The above is the overall process of calculating the SOC value of the battery cell provided for the present disclosure.

In order to accurately determine the single batteries needing to be balanced, the embodiment of the disclosure provides that firstly, the SOC value of at least one single battery in the battery pack is obtained, then, according to the SOC value of at least one single battery in the battery pack, it is determined which of three intervals (0, soc1), (SOC 1, SOC 2), and (SOC 2, 100%) the SOC value of the at least one single battery belongs to, and then, it is determined whether the SOC difference value or the load voltage difference value is selected for use, so as to determine the single batteries needing to be balanced.

Optionally, the method further comprises: and determining the value of SOC1 and the value of SOC2 according to the corresponding relation between the open-circuit voltage OCV and the SOC of the single battery.

The values of SOC1 and SOC2 can be determined according to the corresponding relation between the open-circuit voltage OCV and the SOC of the single battery. In one embodiment, the correspondence relationship of the open-circuit voltage OCV with the SOC satisfies that the rate of change of the OCV with the SOC in the section (SOC 1, SOC 2) is less than a specified value, and the rate of change in the section (0, soc1) and the section (SOC 2, 100%) is greater than or equal to the specified value. In one embodiment, the specified value is a sampling precision of the voltage.

Determining whether to select the SOC difference value or the load voltage difference value to determine the single battery to be balanced, which includes but is not limited to the following two embodiments:

the first embodiment: when the number of the single batteries belonging to the interval (0, SOC1) in the SOC values of the single batteries in the battery pack is greater than or equal to a first preset value, determining to adopt a load voltage difference value to determine the single batteries needing to be balanced; when the number of SOC values belonging to intervals (SOC 1 and SOC 2) in the SOC values of each single battery in the battery pack is larger than or equal to a second preset value, determining to adopt an SOC difference value to determine the single battery needing to be balanced; and when the number of the SOC values belonging to the interval (SOC 2, 100%) in the SOC values of the single batteries in the battery pack is greater than or equal to a third preset value, determining the single batteries needing balancing by adopting the load voltage difference.

Referring to fig. 6, during the charge or discharge of the battery pack, when the SOC values of the unit cells are in the intervals (0, soc1) and (SOC 2, 100%), the uniformity difference of the unit cells is evaluated by the load voltage difference to determine the unit cells requiring the balancing. When the SOC values of the single batteries are in the intervals (SOC 1 and SOC 2), the electric quantity charged or discharged by the single batteries is obtained through an ampere-hour integration method, so that the real-time SOC values of the single batteries are determined, errors caused by the calculation of the SOC values by using voltage can be avoided, and the reliability of the SOC can be effectively improved. Thus, in the intervals (SOC 1, SOC 2), the uniformity difference of the single batteries is evaluated through the SOC difference value so as to determine the single batteries needing to be balanced.

Therefore, in one embodiment of the disclosure, when the number of the SOC values of each single battery in the battery pack belonging to the interval (0, SOC1) is greater than or equal to a first preset value (for example, 1/3 of the total number of the single batteries in the battery pack), the load voltage difference is determined to be adopted to determine the single batteries needing balancing.

And when the number of the SOC values belonging to the (SOC 1, SOC 2) in the SOC values of the single batteries in the battery pack is greater than or equal to a second preset value (for example, 1/2 of the total number of the single batteries in the battery pack), determining to adopt the SOC difference value to determine the single batteries needing to be balanced.

And when the number of SOC values belonging to (SOC 2, 100%) in the SOC values of the single batteries in the battery pack is greater than or equal to a third preset value (for example, 1/3 of the total number of the single batteries in the battery pack), determining to adopt the load voltage difference value to determine the single batteries needing balancing.

That is, if the SOC values of the majority of the unit cells in the battery pack belong to the interval (0, soc1) or (SOC 2, 100%), it is determined that the difference between the load voltages is used to determine the unit cells requiring the balancing, and if the SOC values of the majority of the unit cells in the battery pack belong to the interval (SOC 1, SOC 2), it is determined that the difference between the SOC values is used to determine the unit cells requiring the balancing.

The second embodiment:

determining a reference SOC value required by balancing according to the SOC value of at least one single battery in the battery pack; when the reference SOC value belongs to an interval (SOC 1, SOC 2), determining to adopt an SOC difference value to determine the single battery needing to be balanced; otherwise, determining to adopt the load voltage difference value to determine the single battery needing to be balanced.

In the second embodiment, the reference SOC value may be an SOC value of any one unit cell in the battery pack, for example: the SOC value of the cell having the largest SOC value in the battery pack, or the SOC value of the cell having the smallest SOC value in the battery pack, or the SOC value of the cell having the SOC value aligned in the middle in the battery pack (for the case where the battery pack includes an odd number of cells).

The reference SOC value may also be calculated according to the SOC values of the individual cells in the battery pack, for example: the average value of the SOC values of the respective unit cells in the battery pack, or the average value of the SOC values of the two unit cells in the battery pack having the SOC values arranged at the middle (for the case where the battery pack includes an even number of unit cells).

Comparing the reference SOC value with (SOC 1, SOC 2), and if the reference SOC value belongs to (SOC 1, SOC 2), selecting the SOC difference value to determine the single battery needing to be balanced; and if the reference SOC value does not belong to (SOC 1, SOC 2), selecting the load voltage difference value to determine the single battery needing to be balanced.

The above process is to select the SOC difference value or the load voltage difference value to determine the single battery needing to be balanced. The following describes a case where the SOC difference value is selected to determine the single battery to be balanced, and a case where the load voltage difference value is selected to determine the single battery to be balanced.

First, a case where the SOC difference value is selected to determine the unit cells requiring the balancing will be described. The method specifically comprises the following steps:

acquiring a reference SOC value required by balancing;

determining an SOC difference value between the SOC value of the at least one single battery and a reference SOC value required for balancing, wherein the reference SOC value required for balancing is determined according to the SOC values of the single batteries in the battery pack;

For the description of the reference SOC value required for the equalization determination, reference may be made to the foregoing description, and details are not repeated here. The first equalization starting threshold is a threshold used for determining whether equalization is started for any single battery in the battery pack, that is, a threshold used for judging whether any single battery in the battery pack is a single battery needing equalization.

Firstly, at least one single battery is selected from a battery pack, and then the SOC value of the selected at least one single battery is subtracted from a reference SOC value to obtain the SOC difference value of the selected at least one single battery. Then comparing the obtained SOC difference value with a first balance starting threshold value, and if the SOC difference value of one single battery is greater than or equal to the first balance starting threshold value, determining that the battery is a single battery needing balance; and if the SOC difference value of one single battery is smaller than the first balance starting threshold value, the battery is a single battery which does not need to be balanced.

The reference SOC values are different, the selected at least one single battery is different, and the balancing process of the single battery needing balancing is different. Hereinafter, the reference SOC values are respectively described as the minimum value, the maximum value, and the average value among the SOC values of the respective unit cells in the assembled battery.

1) In a case that the reference SOC value is a minimum value among the SOC values of the respective unit batteries in the battery pack, the determining an SOC difference value between the SOC value of the at least one unit battery and the reference SOC value required for the equalization determination includes: determining an SOC difference value between the SOC values of the following single batteries and a reference SOC value required by balance judgment:

the single battery with the maximum SOC value in the battery pack; or

Correspondingly, after determining that the single battery needing to be equalized is the single battery with the SOC difference value larger than or equal to the first equalization starting threshold value in the at least one single battery, the method further includes: and controlling the discharge of the single battery of which the SOC difference value is greater than or equal to the first balance starting threshold value in the at least one single battery.

Specifically, when the reference SOC value is the minimum value among the SOC values of the individual batteries in the battery pack, only the SOC value of the individual battery with the largest SOC value in the battery pack may be subtracted from the reference SOC value, and it may be determined whether the individual battery with the largest SOC value in the battery pack is the individual battery requiring equalization. This embodiment can only determine whether one cell needs to be balanced.

When the reference SOC value is the minimum value among the SOC values of the individual batteries in the battery pack, the difference between the SOC values of the individual batteries other than the individual battery with the minimum SOC value in the battery pack and the reference SOC value may be made, and it may be determined whether the individual batteries other than the individual battery with the minimum SOC value in the battery pack are the individual batteries requiring equalization. This embodiment is a batch determination method, and can determine whether the other cells except the cell with the smallest SOC value in the battery pack are the cells that need to be balanced at one time.

When the reference SOC value is the minimum value among the SOC values of the individual cells in the battery pack, the process of balancing the individual cells to be balanced is: no matter the battery pack is in a charging state or a discharging state, passive equalization is adopted, and the single batteries needing equalization are discharged.

2) In a case where the reference SOC value is a maximum value among SOC values of the respective unit batteries in the battery pack, the determining an SOC difference value between the SOC value of the at least one unit battery and a reference SOC value required for the equalization determination includes: determining an SOC difference value between the SOC values of the following single batteries and a reference SOC value required by balance judgment:

the single battery with the minimum SOC value in the battery pack; or

Correspondingly, after determining that the single battery needing to be balanced is the single battery with the SOC difference value larger than or equal to the first balancing start threshold value in the at least one single battery, the method further includes: and controlling the charging of the single battery with the SOC difference value larger than or equal to the first equalization starting threshold value in the at least one single battery.

Specifically, when the reference SOC value is the maximum value among the SOC values of the individual batteries in the battery pack, only the SOC value of the individual battery with the minimum SOC value in the battery pack may be subtracted from the reference SOC value, and it may be determined whether the individual battery with the minimum SOC value in the battery pack is the individual battery requiring equalization. This embodiment can only determine whether one cell needs to be balanced.

When the reference SOC value is the maximum value among the SOC values of the individual batteries in the battery pack, the difference between the SOC values of the individual batteries other than the individual battery having the maximum SOC value in the battery pack and the reference SOC value may be made, and it may be determined whether the individual batteries other than the individual battery having the minimum SOC value in the battery pack are the individual batteries requiring equalization. This embodiment is a batch determination method, and can determine whether or not the other cells in the battery pack, except the cell with the largest SOC value, are the cells that need to be balanced at one time.

In the case that the reference SOC value is the maximum value among the SOC values of the individual cells in the battery pack, the process of equalizing the individual cells requiring equalization is as follows: no matter the battery pack is in a charging state or a discharging state, active equalization is adopted to charge the single batteries needing equalization.

3) In a case that the reference SOC value is an average value of the SOC values of the respective unit batteries in the battery pack, the determining an SOC difference value between the SOC value of the at least one unit battery and the reference SOC value required for the equalization determination includes: and determining the SOC difference value between the SOC value of each single battery in the battery pack and the reference SOC value.

Correspondingly, after determining that the single battery needing to be balanced is the single battery with the SOC difference value larger than or equal to the first balancing start threshold value in the at least one single battery, the method further includes:

Specifically, when the reference SOC value is an average value of the SOC values of the individual batteries in the battery pack, the SOC value of each individual battery in the battery pack may be different from the reference SOC value, so as to determine whether each individual battery in the battery pack is an individual battery that needs to be balanced. The embodiment is a batch judgment mode, and can judge whether each single battery in the battery pack is a single battery needing to be balanced at one time.

When the reference SOC value is an average value of the SOC values of the individual cells in the battery pack, the process of equalizing the individual cells to be equalized is as follows: whether the battery pack is in a charging state or a discharging state, the single batteries of which the SOC values are larger than the average value in the single batteries needing to be balanced are passively balanced, and the single batteries of which the SOC values are larger than the average value in the single batteries needing to be balanced are discharged; and adopting active equalization for the single batteries with the SOC values smaller than the average value in the single batteries needing equalization, and charging the single batteries with the SOC values smaller than the average value in the single batteries needing equalization.

Optionally, in combination with the above embodiments, the method further includes:

After the single battery needing to be balanced is determined, the target balancing time length of the single battery needing to be balanced can be determined, and then the single battery needing to be balanced is balanced according to the determined target balancing time length. The target equalization duration is determined according to the SOC value of the single battery needing equalization and a reference SOC value.

Optionally, the target equalization duration of the single battery to be equalized is determined according to the SOC value and the reference SOC value of the single battery to be equalized, and there are two determination methods without limitation:

1) The first way of determining comprises the following steps:

as Δ Q = Δ SOC × C _n Determining the electric quantity difference, wherein delta Q is the electric quantity difference, and delta SOC is the electric quantity difference to be equalizedSOC difference between SOC value of battery cell and reference SOC value, C _n The available capacity of the single batteries to be balanced; and determining a target equalization time length according to t = delta Q/I, wherein t is the target equalization time length, and I is the equalization current of the single battery to be equalized.

2) The second determination method includes the steps of:

and determining the target equalization time length of the single battery to be equalized according to the SOC difference between the SOC value of the single battery to be equalized and the reference SOC value and the corresponding relation between the preset SOC difference and the target equalization time length.

In one embodiment of the present disclosure, the correspondence between the SOC difference value and the target equalization duration is obtained through measurement. After the SOC difference between the SOC value of the single battery to be balanced and the reference SOC value is obtained, the corresponding relation between the SOC difference and the target balancing duration is inquired, and the target balancing duration can be determined.

Next, a case where the load voltage difference is selected to determine the unit cells requiring the balancing will be described. The method specifically comprises the following steps:

determining a reference load voltage value required for balance judgment according to the load voltage value of each single battery in the battery pack;

The description of the reference load voltage value required for the balancing determination is similar to the description of the reference SOC value required for the balancing determination, and the reference load voltage value may be a load voltage value of any single battery in the battery pack, for example: the load voltage value of the single battery with the largest load voltage value in the battery pack, or the load voltage value of the single battery with the smallest load voltage value in the battery pack, or the load voltage value of the single battery with the load voltage value arranged in the middle in the battery pack (for the case that the battery pack includes an odd number of single batteries).

The reference load voltage value may also be calculated according to the load voltage values of the individual cells in the battery pack, for example: the average value of the load voltage values of the respective unit cells in the battery pack, or the average value of the load voltage values of the two unit cells in the battery pack with the load voltage values arranged at the middle (for the case where the battery pack includes an even number of unit cells).

The second equalization enable threshold may be the same as or different from the first equalization enable threshold. Both of the two thresholds are used for determining whether to start balancing for any single battery in the battery pack, that is, for judging whether any single battery in the battery pack is a single battery needing balancing.

Firstly, at least one single battery is selected from a battery pack, and then the load voltage value of the selected at least one single battery is differenced with a reference load voltage value to obtain the load voltage difference value of the selected at least one single battery. Then comparing the obtained load voltage difference value with a second balance starting threshold value, and if the load voltage difference value of one single battery is greater than or equal to the second balance starting threshold value, the battery is the single battery needing to be balanced; and if the load voltage difference value of one single battery is smaller than the second balance starting threshold value, the battery is a single battery which does not need to be balanced.

The reference load voltage values are different, the selected at least one single battery is different, and the balancing process of the single battery needing to be balanced is different. Hereinafter, the reference load voltage values will be described as the minimum value, the maximum value, and the average value among the load voltage values of the respective unit cells in the battery pack.

1) In a case that the reference load voltage value is a minimum value among load voltage values of the individual batteries in the battery pack, the determining a load voltage difference value between the load voltage value of the at least one individual battery and a reference load voltage value required for the balancing determination includes: determining a load voltage difference value between the load voltage value of the following single batteries and a reference load voltage value required by balance judgment:

the single battery with the largest load voltage value in the battery pack; or

Correspondingly, after determining that the single battery needing to be balanced is the single battery with the load voltage difference value greater than or equal to the second balancing start threshold value in the at least one single battery, the method further includes: and controlling the discharge of the single battery with the load voltage difference value greater than or equal to the second balance starting threshold value in the at least one single battery.

Specifically, when the reference load voltage value is the minimum value among the load voltage values of the individual batteries in the battery pack, only the load voltage value of the individual battery with the largest load voltage value in the battery pack may be subtracted from the reference load voltage value, so as to determine whether the individual battery with the largest load voltage value in the battery pack is the individual battery that needs to be balanced. This embodiment can only determine if one cell needs to be balanced.

When the reference load voltage value is the minimum value among the load voltage values of the single batteries in the battery pack, the load voltage values of the other single batteries except the single battery with the minimum load voltage value in the battery pack can be differentiated from the reference load voltage value, so as to judge whether the other single batteries except the single battery with the minimum load voltage value in the battery pack are the single batteries needing balancing. This embodiment is a batch determination method, and can determine whether or not the other cells in the battery pack, except the cell with the smallest load voltage value, are the cells that need to be balanced at one time.

Under the condition that the reference load voltage value is the minimum value of the load voltage values of the single batteries in the battery pack, the process of balancing the single batteries needing to be balanced is as follows: no matter the battery pack is in a charging state or a discharging state, passive equalization is adopted, and the single batteries needing equalization are discharged.

2) In a case that the reference load voltage value is a maximum value among load voltage values of the individual batteries in the battery pack, the determining a load voltage difference value between the load voltage value of the at least one individual battery and a reference load voltage value required for the balancing determination includes: determining a load voltage difference value between the load voltage value of the following single batteries and a reference load voltage value required by balance judgment:

the single battery with the minimum load voltage value in the battery pack; or

Correspondingly, after determining that the single battery needing to be balanced is the single battery with the load voltage difference value greater than or equal to the second balancing start threshold value in the at least one single battery, the method further includes: and controlling the charging of the single battery with the load voltage difference value greater than or equal to the second balance starting threshold value in the at least one single battery.

Specifically, when the reference load voltage value is the maximum value among the load voltage values of the individual batteries in the battery pack, only the load voltage value of the individual battery with the smallest load voltage value in the battery pack may be subtracted from the reference load voltage value, and it may be determined whether the individual battery with the smallest load voltage value in the battery pack is the individual battery that needs to be balanced. This embodiment can only determine whether one cell needs to be balanced.

When the reference load voltage value is the maximum value among the load voltage values of the single batteries in the battery pack, the load voltage values of the other single batteries except the single battery with the maximum load voltage value in the battery pack can be subtracted from the reference load voltage value, so as to determine whether the other single batteries except the single battery with the minimum load voltage value in the battery pack are the single batteries needing balancing. This embodiment is a batch determination method, and can determine whether or not the other cells in the battery pack, except the cell with the largest load voltage value, are the cells that need to be balanced at one time.

Under the condition that the reference load voltage value is the maximum value of the load voltage values of the single batteries in the battery pack, the process of balancing the single batteries needing to be balanced is as follows: no matter the battery pack is in a charging state or a discharging state, active equalization is adopted to charge the single batteries needing equalization.

3) In a case that the reference load voltage value is an average value of load voltage values of the individual batteries in the battery pack, the determining a load voltage difference value between the load voltage value of the at least one individual battery and a reference load voltage value required for the balancing determination includes: and determining a load voltage difference value between the load voltage value of each single battery in the battery pack and the reference load voltage value.

Correspondingly, after it is determined that the cell needing to be balanced is the cell whose load voltage difference value in the at least one cell is greater than or equal to the second balancing start threshold, the method further includes:

and for any single battery of which the load voltage difference value is greater than or equal to the second balance starting threshold value in the at least one single battery, when the load voltage value of the single battery is greater than the reference load voltage value, controlling the single battery to discharge, and when the load voltage value of the single battery is less than the reference load voltage value, controlling the single battery to charge.

Specifically, when the reference load voltage value is an average value of the load voltage values of the individual batteries in the battery pack, only the load voltage value of each individual battery in the battery pack may be subtracted from the reference load voltage value, and it may be determined whether each individual battery in the battery pack is an individual battery that needs to be balanced. The embodiment is a batch judgment mode, and can judge whether each single battery in the battery pack is a single battery needing to be balanced at one time.

Under the condition that the reference load voltage value is the average value of the load voltage values of all the single batteries in the battery pack, the process of balancing the single batteries needing to be balanced is as follows: whether the battery pack is in a charging state or a discharging state, the passive balancing is adopted for the single batteries of which the load voltage values in the single batteries to be balanced are larger than the average value, and the single batteries of which the load voltage values in the single batteries to be balanced are larger than the average value are discharged; and actively balancing the single batteries with the load voltage values smaller than the average value in the single batteries to be balanced, and charging the single batteries with the load voltage values smaller than the average value in the single batteries to be balanced.

After the single batteries needing to be balanced are determined, the target balancing time length of the single batteries needing to be balanced can be determined, and then the single batteries needing to be balanced are balanced according to the determined target balancing time length. The target balancing time length is determined according to the load voltage value of the single battery needing to be balanced and the reference load voltage value.

Optionally, the target balancing duration of the single battery to be balanced is determined according to the load voltage value and the reference load voltage value of the single battery to be balanced, and there are three determination methods without limitation:

1) The first way of determining comprises the following steps:

determining a first SOC value corresponding to the reference load voltage value according to the reference load voltage value and an open-circuit voltage OCV-remaining capacity SOC curve of the battery pack; determining a second SOC value corresponding to the load voltage value of the single battery to be balanced according to the load voltage value of the single battery to be balanced and the OCV-SOC curve; and determining the target equalization time length according to the first SOC value and the second SOC value.

Optionally, the determining, according to the reference load voltage value and an open-circuit voltage OCV-remaining capacity SOC curve of the battery pack, a first SOC value corresponding to the reference load voltage value includes: determining the single battery with the minimum difference between the load voltage value and the reference load voltage value in the battery pack as a reference battery; determining a reference OCV value of the reference battery according to the load voltage value of the reference battery and the internal resistance value of the reference battery; determining an SOC value corresponding to the reference OCV value as the first SOC value according to the reference OCV value and the OCV-SOC curve;

the determining a second SOC value corresponding to the load voltage value of the single battery to be balanced according to the load voltage value of the single battery to be balanced and the OCV-SOC curve comprises the following steps: determining the OCV value of the single battery to be balanced according to the load voltage value of the single battery to be balanced and the internal resistance value of the single battery to be balanced; and determining the SOC value corresponding to the OCV value of the single battery to be balanced as the second SOC value according to the OCV-SOC curve.

In one embodiment of the present disclosure, the OCV-SOC curve is obtained through measurement. For example, in the process of changing the SOC value of a certain unit cell from 0 to 100%, the open-circuit voltage OCV of the primary cell is measured at certain SOC intervals, and then the OCV and the SOC corresponding to each point are mapped one-to-one to form the SOC-OCV curve of the unit cell.

It should be understood that, when the open circuit voltage OCV is measured, the load voltage of the unit cell may be collected and then converted into the corresponding open circuit voltage OCV according to equation (1).

Therefore, the first SOC value of the reference battery can be obtained according to the reference voltage value, the internal resistance value of the reference battery and the OCV-SOC curve corresponding to the reference battery. And acquiring a second SOC value of the single battery to be balanced according to the voltage value of the single battery to be balanced, the internal resistance value of the single battery to be balanced and the OCV-SOC curve corresponding to the single battery to be balanced.

After obtaining the first SOC-value and the second SOC-value, performing the steps of:

as Δ Q = Δ SOC × C _n Determining a difference in electrical quantities, where Δ Q is the difference in electrical quantities, Δ SOC is the difference in SOC between a first SOC value and a second SOC value, C _n To be equalized by a single bodyThe available capacity of the pool;

and determining a target equalization time length according to t = delta Q/I, wherein t is the target equalization time length, and I is the equalization current of the single battery to be equalized.

2) The second determination method includes the steps of:

and determining the target balancing time length of the single battery to be balanced according to the load voltage difference between the load voltage value of the single battery to be balanced and the reference load voltage value and the corresponding relation between the preset load voltage difference and the target balancing time length.

In one embodiment of the present disclosure, the correspondence between the load voltage difference and the target balancing time period is obtained through measurement. After a load voltage difference value between the load voltage value of the single battery to be balanced and the reference load voltage value is obtained, the corresponding relation between the load voltage difference value and the target balancing time length is inquired, and the target balancing time length can be determined.

It should be understood that, referring to the following table 1, when the battery performance parameters are the SOC value, the internal resistance value, the self-discharge rate, the voltage change rate, the electric quantity change rate, or the time change rate, respectively, the correspondence table of the equalization judgment and the equalization manner.

The self-discharge rate of the single battery is used for representing the capacity loss condition and the capacity loss rate of the single battery. In one embodiment, when the battery pack stops working and reaches a stable state (at the time t 1), detecting and recording an open-circuit voltage value V1 of each single battery of the battery pack; when the battery pack starts to work again (at the moment of t 2), detecting and recording the open-circuit voltage value V2 of each single battery of the battery pack; calculating the self-discharge rate eta of each single battery according to the open-circuit voltage value of each single battery obtained by two times of detection, wherein the calculation method of the self-discharge rate eta comprises the following steps:

(1) Finding out corresponding SOC1 and SOC2 according to the detected V1 and V2 based on the OCV-SOC curve of the battery;

(2) Calculating the SOC change value delta SOC of the battery according to the SOC1 and the SOC2;

(3) Calculating the battery capacity discharged by the battery through self-discharge according to the delta SOC and the full-capacity C of the battery, wherein delta Q = delta SOC C;

(4) Calculating the value of the self-discharge rate eta of the battery: η = Δ Q/(t 1-t 2).

The voltage change rate of the unit cells may be a voltage change amount at which a unit change of a specified physical quantity of the unit cells occurs. For example, in the present disclosure, to charge or discharge a preset amount of electricity to or from a battery cell, a voltage variation (dv/dq) of the battery cell; or, a preset time period for charging or discharging the single battery, and a voltage variation (dv/dt) of the single battery will be described as an example.

The rate of change of charge (dq/dv) of the unit cell may be an amount of change in charge when a unit of a specified physical quantity of the unit cell is changed. For example, the present disclosure will be described by taking as an example the amount of electricity charged necessary for the voltage of the unit cell to rise by one unit voltage from the initial voltage, or the amount of electricity decreased by the voltage of the unit cell to fall by one unit voltage from the initial voltage.

The time change rate (dt/dv) of the unit cell may be a time period required for a unit change of a specific physical quantity of the unit cell. For example, the present disclosure will be described taking as an example a charging time required for the voltage of the unit cell to rise by one unit voltage from the initial voltage, or a discharging time required for the voltage of the unit cell to fall by one unit voltage from the initial voltage.

TABLE 1

Therefore, when different battery performance parameters are adopted for equalization judgment, the equalization judgment is carried out according to the corresponding equalization judgment method in the table 1, and the single batteries needing equalization in the battery pack are determined.

It should be understood that if it is determined that there is no single battery needing to be balanced, whether there is a single battery needing to be balanced is continuously judged according to the SOC value of at least one single battery in the battery pack. When it is determined that no single battery needs to be balanced, the control module does not act, so that the balancing module corresponding to any battery is not started.

Fig. 8 is a schematic diagram of an equalization module according to an embodiment of the disclosure. And controlling the single batteries to be balanced, wherein the balancing judgment needs to be combined. And according to the step of equalization judgment, determining whether the equalization mode of the single battery to be equalized is passive equalization (namely, the single battery to be equalized is discharged) or active equalization (namely, the single battery to be equalized is charged), and conducting the corresponding equalization module.

Referring to fig. 8, for passive equalization, the equalization module includes: and each single battery corresponds to one equalizing module, namely two ends of each single battery are connected with one resistor in parallel.

For the single battery to be balanced which needs to be passively balanced, the control module controls the conduction of a parallel loop between the single battery to be balanced and the corresponding resistor of the single battery to be balanced so as to execute the passive balancing of the single battery. Referring to fig. 8, the control module controls the switch module 812 to be turned on, so as to implement the conduction of the parallel loop between the single battery to be balanced and the corresponding resistor.

The resistor 811 may be a fixed resistor or a variable resistor. In one embodiment, the resistor 811 may be a positive temperature coefficient thermistor, which may change with the temperature change, so as to adjust the balancing current generated during balancing, thereby automatically adjusting the heat generation amount of the battery balancing system, and finally effectively controlling the temperature of the battery balancing system.

Referring to fig. 8, for active equalization, the equalization module includes a charging branch 94 connected in parallel with each battery cell 95 in the battery pack, the charging branches 94 correspond to the battery cells 95 one by one, and each charging branch 94 is connected to the generator 92, and the generator 92 is mechanically connected to the engine 91 through a gear.

For the single battery to be equalized which needs to be actively equalized, the control module controls the charging branch 94 corresponding to the single battery to be equalized to be conducted. When the engine 91 rotates, the generator 92 is driven to generate electricity, so that the electricity generated by the generator 92 is transmitted to the single battery to be balanced, and the electricity of the single battery to be balanced is increased.

Referring to fig. 8, when the generator 92 is an alternator, the equalizing module further comprises a rectifier 93 connected in series with the generator 92, each charging branch 130 being connected in series with the rectifier 132. After the alternating current generated by the generator 92 is converted into direct current by the rectifier 93, the generator 92 can be used for charging the single batteries to be equalized.

Referring to fig. 8, the control module may control the switch 96 corresponding to the single battery to be equalized to be turned on, so that the charging branch corresponding to the single battery to be equalized is turned on, and active equalization of the single battery to be equalized is performed.

In other embodiments, in addition to the charging of the single batteries by the generator shown in fig. 8, the single batteries to be equalized may also be charged by the starting battery in the entire vehicle.

In another embodiment, in addition to the parallel resistor and the single battery to be equalized shown in fig. 8, the single battery to be equalized may be connected in parallel with a starting battery of the whole vehicle, and the electric quantity discharged by the single battery to be equalized is charged into the starting battery, so that the equalization of the single battery to be equalized is realized while energy waste is effectively avoided.

As described above, in the embodiment of the present disclosure, a plurality of single batteries may share one balancing module, and when at least two single batteries among a plurality of single batteries sharing one balancing module need to be balanced, the balancing module is alternately connected to each single battery among the at least two single batteries needing to be balanced, and the balancing module performs balancing respectively.

Correspondingly, the embodiment of the disclosure also provides a vehicle, which comprises the battery equalization system.

Accordingly, the disclosed embodiments also provide a computer readable storage medium, on which computer program instructions are stored, and the program instructions, when executed by a processor, implement the above battery equalization method.

Correspondingly, the embodiment of the present disclosure further provides an electronic device, including: the aforementioned computer-readable storage medium; and one or more processors for executing the program in the computer-readable storage medium.

The preferred embodiments of the present disclosure are described in detail above with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details in the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. In order to avoid unnecessary repetition, various possible combinations will not be separately described in this disclosure.

Claims

1. A method of balancing a battery, comprising:

acquiring the SOC value of at least one single battery in the battery pack;

determining to adopt an SOC difference value or a load voltage difference value to determine the single battery needing to be balanced according to the interval of the SOC value of the at least one single battery;

the determining to adopt the SOC difference value or the load voltage difference value to determine the single battery needing to be balanced according to the interval where the SOC value of at least one single battery in the battery pack is located includes:

when the number of the SOC values belonging to the intervals (SOC 1 and SOC 2) in the SOC values of the single batteries in the battery pack is greater than or equal to a second preset value, determining to adopt an SOC difference value to determine the single batteries needing to be balanced;

when the number of the SOC values belonging to the interval (SOC 2, 100%) in the SOC values of the single batteries in the battery pack is greater than or equal to a third preset value, determining to adopt a load voltage difference value to determine the single batteries needing balancing;

or,

2. The method of claim 1, further comprising:

3. The method according to claim 2, wherein the correspondence relationship between OCV and SOC satisfies: the rate of change of the OCVs with the SOCs in the sections (SOC 1, SOC 2) is less than a prescribed value, and the rate of change in the sections (0, SOC1) and (SOC 2, 100%) is greater than or equal to the prescribed value.

4. The method of claim 1, wherein determining a reference SOC value required for equalization based on the SOC value of at least one cell in the battery pack comprises:

5. The method of claim 3, wherein the specified value is a sampling precision of a voltage.

6. The method of claim 1, wherein when determining to employ the SOC difference value to determine the cell requiring equalization, the method further comprises:

acquiring a reference SOC value required by balancing;

7. The method according to claim 6, wherein the reference SOC value is a minimum value among SOC values of the respective unit cells in the battery pack;

the single battery with the maximum SOC value in the battery pack; or

8. The method according to claim 7, wherein after determining that the cell needing equalization is the cell of which the SOC difference value is greater than or equal to the first equalization starting threshold value in the at least one cell, the method further comprises:

9. The method according to claim 6, wherein the reference SOC value is a maximum value among SOC values of the respective unit cells in the battery pack;

the single battery with the minimum SOC value in the battery pack; or

10. The method according to claim 9, wherein after determining that the cell requiring equalization is the cell whose SOC difference value is greater than or equal to the first equalization start threshold value in the at least one cell, the method further comprises:

and controlling the charging of the single battery with the SOC difference value of the at least one single battery larger than or equal to the first equalization starting threshold value.

11. The method according to claim 6, wherein the reference SOC value is an average of SOC values of the respective unit cells in the battery pack;

12. The method according to claim 11, wherein after determining that the cell requiring equalization is the cell whose SOC difference value in the at least one cell is greater than or equal to the first equalization starting threshold, the method further comprises:

13. The method according to claim 6, wherein after determining that the single battery needing equalization is the single battery with the SOC difference value larger than or equal to the first equalization starting threshold value in the at least one single battery, the method further comprises:

14. The method of claim 1, wherein when it is determined that the load voltage difference is adopted to determine the cell needing balancing, the method further comprises:

15. The method according to claim 14, wherein the reference load voltage value is the minimum value among the load voltage values of the respective unit cells in the battery pack;

the single battery with the largest load voltage value in the battery pack; or

16. The method according to claim 15, wherein after determining that the cell requiring balancing is the cell whose load voltage difference value in the at least one cell is greater than or equal to the second balancing start threshold, the method further comprises:

17. The method according to claim 14, wherein the reference load voltage value is a maximum value among load voltage values of the respective unit cells in the battery pack;

the determining a load voltage difference value between the load voltage value of the at least one cell and the reference load voltage value comprises:

the single battery with the minimum load voltage value in the battery pack; or

18. The method according to claim 17, wherein after determining that the cell needing to be balanced is the cell whose load voltage difference value in the at least one cell is greater than or equal to the second balancing start threshold, the method further comprises:

19. The method according to claim 14, wherein the reference load voltage value is an average value of load voltage values of the respective unit cells in the battery pack;

20. The method according to claim 19, wherein after determining that the cell needing to be balanced is the cell whose load voltage difference value in the at least one cell is greater than or equal to the second balancing start threshold, the method further comprises:

21. The method according to claim 14, wherein after determining that the cell needing to be balanced is the cell whose load voltage difference value in the at least one cell is greater than or equal to the second balancing start threshold, the method further comprises:

22. The method according to claim 1, characterized in that the method of calculating the SOC value comprises a first calculation mode corresponding to the interval (0, soc1) and the interval (SOC 2, 100%) and a second calculation mode corresponding to the interval (SOC 1, SOC 2);

the acquiring of the SOC value of each battery cell in the battery pack includes:

23. The method of claim 22, wherein the first calculation mode is a mode used by the single battery for calculating the SOC value last time.

24. The method according to claim 22 or 23, wherein the first calculation method is ampere-hour integral or ampere-hour integral combined with voltage correction, and the second calculation method is ampere-hour integral combined with a different calculation method from the first calculation method in the voltage correction method.

25. A battery equalization system, comprising:

a balancing module, an acquisition module and a control module,

the balancing module is used for balancing the single batteries needing balancing;

the control module is used for:

or,

the control module is used for:

26. The battery equalization system of claim 25, wherein the control module is configured to:

27. The battery equalization system according to claim 26, wherein the correspondence relationship between OCV and SOC satisfies: the rate of change of the OCVs with the SOCs in the sections (SOC 1, SOC 2) is less than a prescribed value, and the rate of change in the sections (0, SOC1) and (SOC 2, 100%) is greater than or equal to the prescribed value.

28. The battery equalization system of claim 25, wherein the control module is configured to: and determining the SOC value of any single battery in the battery pack as the reference SOC value.

29. The battery equalization system of claim 27, wherein said specified value is a sampling accuracy of a voltage.

30. The battery equalization system of claim 25, wherein the control module is configured to:

acquiring a reference SOC value required by balancing;

31. The battery equalization system of claim 30, wherein the control module is configured to:

the equalization module is configured to:

32. The battery equalization system of claim 25, wherein the control module is configured to:

33. The battery balancing system of claim 32, wherein the reference load voltage value is a minimum value, a maximum value or an average value of the load voltage values of the individual battery cells in the battery pack.

34. The battery equalization system of claim 32, wherein the control module is configured to:

the equalization module is configured to:

35. The battery equalization system of claim 25,

the method of calculating the SOC value comprises a first calculation mode corresponding to the interval (0, SOC1) and the interval (SOC 2, 100%) and a second calculation mode corresponding to the interval (SOC 1, SOC 2);

the acquisition module is used for:

36. The battery equalization system of claim 35, wherein the first calculation method is the last calculation method of the SOC value of the battery cell.

37. The battery equalization system according to claim 35 or 36, wherein the first calculation method is an ampere-hour integral method or an ampere-hour integral combined voltage correction method, and the second calculation method is a calculation method different from the first calculation method in the ampere-hour integral method and the ampere-hour integral combined voltage correction method.

38. The battery equalization system of claim 25, wherein the control module is connected to the acquisition module and the equalization module corresponding to the same cell through a channel, and the control module is configured to control the control module to connect to the corresponding sampling module when it is determined that the cell connected to the control module does not need equalization; or,

39. The battery equalization system of claim 38, wherein the control module comprises a control chip, and the control chip is connected to the acquisition module and the equalization module corresponding to the same cell through one pin and the one channel.

40. The battery equalization system of claim 25, wherein the control module is connected to the acquisition module and the equalization module corresponding to the same cell through two channels.

41. The battery equalization system of claim 40, wherein the control module comprises a control chip, the control chip is connected to the acquisition module and the equalization module corresponding to the same cell through two pins, and the two pins are in one-to-one correspondence with the two channels.

42. A computer-readable storage medium, having computer program instructions stored thereon, which, when executed by a processor, implement the method of any one of claims 1-24.

43. An electronic device, comprising:

the computer-readable storage medium recited in claim 42; and

44. A vehicle, characterized in that the vehicle comprises: a battery pack and a battery equalization system as claimed in any of claims 25-41.