CN117318222A - Method and device for balancing state of charge of battery cell - Google Patents

Abstract

The application discloses a method and a device for balancing the state of charge of a battery cell. And acquiring the difference between the lowest SOC and the highest SOC in the battery SOC of each battery cell in the battery box as the battery cell SOC. And when the cell SOC difference is larger than the equalization threshold value, performing the lowest SOC equalization. And after the lowest SOC equalization is finished, carrying out average SOC equalization. The lowest SOC or the average SOC can be automatically selected as the target electric quantity for balancing under the condition of inconsistent electric quantity of the electric cores. The equalization type is more changeable, and various conditions during SOC equalization can be more accurately adapted. In addition, the SOC equalization can be directly carried out on the single battery cells to be equalized, so that the capacities of all the single battery cells are consistent, one-to-one operation is not needed, the process is simple and convenient, and the efficiency is higher.

Description

Method and device for balancing state of charge of battery cell

Technical Field

The present disclosure relates to the field of power electronics, and in particular, to a method and an apparatus for equalizing a state of charge of a battery cell.

Background

SOC equalization is an important technology in an energy storage system, and the percentage value of the residual electric quantity among all single batteries is kept consistent by monitoring and adjusting the electric quantity in a battery module, so that each battery can be kept in the same state during normal use, the phenomena of overcharge and overdischarge of the battery are avoided, the service life of the battery is prolonged, and the efficiency of the energy storage system is improved.

In the prior art, the electric quantity of each electric core is regulated and controlled independently, so that each electric core is in a full-electricity or empty-electricity state, but the efficiency of the method is low. In addition, each battery cell in the battery module is charged or discharged through the difference between the electric quantity of each battery module and the electric quantity of the reference module. However, there is a certain error, so that the equalization effect is not ideal. Therefore, how to accurately and efficiently balance the electricity Chi Dianliang becomes a problem to be solved.

Disclosure of Invention

Based on the above problems, the application provides a method and a device for balancing the charge state of a battery cell, so as to balance the battery electric quantity accurately and efficiently.

The application discloses a method for equalizing the state of charge of a battery cell, wherein a battery box comprises at least one battery module, and each battery module comprises at least one battery cell, and the method comprises the following steps:

acquiring the difference between the lowest SOC and the highest SOC in the battery core SOC of each battery core in the battery box as the battery core SOC difference;

when the SOC difference of the battery cells is larger than an equalization threshold value, carrying out lowest SOC equalization;

after the lowest SOC equalization is completed, carrying out average SOC equalization; and the average SOC is the average value of the battery core SOC of each battery core in the battery box.

Optionally, after performing the minimum SOC equalization, the method further includes:

and judging whether the lowest SOC equalization is needed again according to the completion time of the lowest SOC equalization, the first preset days, the battery cell SOC, the battery module SOC, the preset module electric quantity and the self-discharge threshold value.

Optionally, the determining whether the minimum SOC equalization needs to be performed again according to the completion time of the minimum SOC equalization, the first preset days, the battery core SOC, the battery module SOC, the preset module electric quantity and the self-discharge threshold includes:

if the current time is longer than the completion time by the first preset number of days, acquiring a battery module SOC in the battery box, and judging whether minimum SOC equalization is needed again according to the battery module SOC, the preset module electric quantity, the battery core SOC and the self-discharge threshold;

and if the current time is not longer than the completion time by the first preset days, carrying out average SOC equalization.

Optionally, the determining whether the lowest SOC equalization needs to be performed again according to the battery module SOC, the preset module electric quantity, the battery cell SOC, and the self-discharge threshold includes:

obtaining the difference between the lowest battery module SOC and the highest battery module SOC in the battery module SOC of each battery module in the battery box as a module SOC difference;

when the module SOC difference is larger than the preset module electric quantity, judging whether the lowest SOC equalization is needed to be performed again according to the battery cell SOC difference and the self-discharge threshold value;

and when the module SOC difference is smaller than or equal to the preset module electric quantity, carrying out lowest SOC equalization again.

Optionally, the determining whether the lowest SOC equalization needs to be performed again according to the SOC difference of the battery cell and the self-discharge threshold includes:

when the battery cell SOC difference is larger than the self-discharge threshold value, carrying out average SOC equalization;

when the battery cell SOC difference is smaller than or equal to the self-discharge threshold value, judging whether the battery cell SOC difference is larger than the preset electric quantity or not;

if yes, carrying out the lowest SOC balance again;

if not, the average SOC equalization is performed.

Optionally, performing the lowest SOC equalization or the average SOC equalization includes:

when the lowest SOC is balanced, taking the lowest SOC as a reference SOC;

when average SOC equalization is performed, taking the average SOC as a reference SOC;

acquiring the difference between the battery cell SOC of the battery cell to be balanced and the reference SOC as the electric quantity to be balanced; the battery cell to be balanced is in the battery box, and the difference between the battery cell SOC and the reference SOC is larger than the preset electric quantity;

and controlling the equalization current and the equalization time according to the electric quantity to be equalized so as to perform reference SOC equalization on the electric core to be equalized.

Optionally, performing reference SOC equalization includes:

when the electric quantity to be balanced is 0, stopping carrying out reference SOC balance on the electric core to be balanced;

when the on-board temperature is greater than the maximum allowable temperature, stopping performing reference SOC equalization on the battery cells to be equalized;

and stopping carrying out reference SOC equalization on the battery cells to be equalized when the battery cell SOC of the battery cells to be equalized is lower than the discharge cut-off electric quantity.

Optionally, the performing the minimum SOC equalization includes:

recording the start time of the lowest SOC balance;

judging whether the current time is more than a second preset number of days from the starting time;

if yes, stopping carrying out the lowest SOC balance;

if not, stopping balancing the lowest SOC until the difference of the battery core SOCs is smaller than or equal to the preset electric quantity.

Optionally, after performing the reference SOC equalization, the method further includes:

when the battery cell SOC in the battery box is lower than the undervoltage power-on SOC or the battery cell voltage in the battery box is lower than the discharge cut-off voltage, charging the battery box;

when the SOC of the battery cell in the battery box is higher than the discharge cut-off SOC, stopping charging the battery box;

and stopping charging the battery box when the lowest cell voltage in the cell voltages of each cell is larger than the plateau voltage.

Based on the method for balancing the charge state of the battery core, the application also discloses a device for balancing the charge state of the battery core, which comprises the following steps: the device comprises a difference value acquisition unit, a threshold value judgment unit and an equalization unit;

the difference value acquisition unit is used for acquiring the difference between the lowest SOC and the highest SOC in the battery core SOC of each battery core in the battery box as the battery core SOC difference;

the threshold value judging unit is used for carrying out lowest SOC equalization when the battery cell SOC difference is larger than an equalization threshold value;

the balancing unit is used for carrying out average SOC balancing after the lowest SOC balancing is completed; and the average SOC is the average value of the battery core SOC of each battery core in the battery box.

Optionally, the apparatus further includes:

and the equalization judging unit is used for judging whether the lowest SOC equalization is needed to be performed again according to the completion time of the lowest SOC equalization, the first preset days, the battery core SOC, the battery module SOC, the preset module electric quantity and the self-discharge threshold value.

Optionally, the equalization judging unit includes:

the first judging subunit is configured to obtain the battery module SOC in the battery box if the current time is greater than the first preset number of days from the completion time, and judge whether minimum SOC equalization is needed again according to the battery module SOC, the preset module electric quantity, the battery core SOC and the self-discharge threshold;

and the first day number judging subunit is used for carrying out average SOC equalization if the current time is not longer than the first preset days from the completion time.

Optionally, the first judging subunit includes:

a difference value obtaining subunit, configured to obtain, as a module SOC difference, a difference between a lowest battery module SOC and a highest battery module SOC in the battery module SOC of each battery module in the battery box;

the second judging subunit is used for judging whether the lowest SOC equalization is needed again according to the battery cell SOC difference and the self-discharge threshold value when the module SOC difference is larger than the preset module electric quantity;

and the module electric quantity judging subunit is used for carrying out lowest SOC equalization again when the module SOC difference is smaller than or equal to the preset module electric quantity.

Optionally, the second judging subunit includes:

a discharge threshold judging subunit, configured to perform average SOC equalization when the battery cell SOC difference is greater than the self-discharge threshold;

the electric quantity judging subunit is used for judging whether the electric core SOC difference is larger than the preset electric quantity or not when the electric core SOC difference is smaller than or equal to the self-discharge threshold value;

a lowest equalization subunit, configured to perform lowest SOC equalization again;

and the average equalization subunit is used for carrying out average SOC equalization.

Optionally, the equalization unit includes:

a lowest reference subunit, configured to take a lowest SOC as a reference SOC when performing lowest SOC equalization;

an average reference subunit, configured to take the average SOC as a reference SOC when performing average SOC equalization;

the electric quantity to be balanced obtaining subunit is used for obtaining the difference between the battery cell SOC of the battery cell to be balanced and the reference SOC as the electric quantity to be balanced; the battery cell to be balanced is in the battery box, and the difference between the battery cell SOC and the reference SOC is larger than the preset electric quantity;

and the reference equalization subunit is used for controlling equalization current and equalization duration according to the electric quantity to be equalized so as to perform reference SOC equalization on the electric core to be equalized.

Optionally, the reference equalization subunit includes:

the electric quantity to be balanced judging subunit is used for stopping carrying out reference SOC balance on the electric core to be balanced when the electric quantity to be balanced is 0;

the temperature judging subunit is used for stopping carrying out reference SOC equalization on the battery cells to be equalized when the on-board temperature is greater than the maximum allowable temperature;

and the power cut-off judging subunit is used for stopping carrying out reference SOC equalization on the battery cells to be equalized when the battery cell SOC of the battery cells to be equalized is lower than the discharge power cut-off.

Optionally, the threshold value judging unit includes:

a time recording subunit, configured to record the start time of the lowest SOC equalization;

a second day judging subunit, configured to judge whether the current time is greater than a second preset day from the opening time;

a stop equalization subunit configured to stop performing the lowest SOC equalization;

and stopping the lowest SOC equalization until the difference of the battery cell SOCs is smaller than or equal to the preset electric quantity.

Optionally, the apparatus further includes:

the under-voltage power-up judging subunit is used for charging the battery box when the SOC of the battery cell in the battery box is lower than the under-voltage power-up SOC or the voltage of the battery cell in the battery box is lower than the discharge cut-off voltage;

a discharge cut-off judging subunit, configured to stop charging the battery box when the SOC of the battery cell in the battery box is higher than the discharge cut-off SOC;

and the platform-stage voltage judging subunit is used for stopping charging the battery box when the lowest cell voltage in the cell voltages of each cell is larger than the platform-stage voltage.

The application discloses a method and a device for balancing the state of charge of a battery cell. And acquiring the difference between the lowest SOC and the highest SOC in the battery SOC of each battery cell in the battery box as the battery cell SOC. And when the cell SOC difference is larger than the equalization threshold value, performing the lowest SOC equalization. And after the lowest SOC equalization is finished, carrying out average SOC equalization. The lowest SOC or the average SOC can be automatically selected as the target electric quantity for balancing under the condition of inconsistent electric quantity of the electric cores. The equalization type is more changeable, and various conditions during SOC equalization can be more accurately adapted. In addition, the SOC equalization can be directly carried out on the single battery cells to be equalized, so that the capacities of all the single battery cells are consistent, one-to-one operation is not needed, the process is simple and convenient, and the efficiency is higher.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present application, and that other drawings may be obtained according to the provided drawings without inventive effort to a person skilled in the art.

Fig. 1 is a schematic flow chart of a method for equalizing charge states of battery cells according to an embodiment of the present disclosure;

FIG. 2 is a flow chart of another method for balancing the state of charge of a battery cell according to an embodiment of the present disclosure;

FIG. 3 is a flow chart of another method for balancing the state of charge of a battery cell according to an embodiment of the present disclosure;

fig. 4 is a schematic structural diagram of a device for equalizing charge states of electric cells according to an embodiment of the present application.

Detailed Description

In the field of batteries, batteries are commonly referred to as batteries, and cells, modules, and battery cases are different stages in battery applications. In the battery box, in order to safely and effectively manage hundreds or thousands of single battery cells, the battery cells are not randomly placed in the shell of the battery box, but are orderly placed according to modules. The minimum unit is a battery cell, a group of battery cells can form a module, and a plurality of modules can form a battery box. The SOC of the battery cell, i.e. the state of charge of the battery cell, is used to reflect the remaining capacity of the battery cell, and is defined as the ratio of the remaining capacity to the total capacity, and is usually expressed as a percentage.

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

Embodiment one: the application discloses a method for balancing a charge state of a battery cell.

Specifically, referring to fig. 1, a method for equalizing the state of charge of a battery cell disclosed in this embodiment includes the following steps:

step 101: and acquiring the difference between the lowest SOC and the highest SOC in the battery SOC of each battery cell in the battery box as the battery cell SOC difference.

In the method of the present embodiment, SOC equalization is continuously performed, and the default SOC equalization mode is the average SOC equalization mode. The average SOC is the average of the cell SOCs of each cell in the battery case.

As an optional method, the battery box may be first subjected to static calibration, specifically, the battery cells in the battery box are static for a preset time, and the voltage value of each battery cell may be obtained. And judging whether the voltage value of each battery cell is in an allowable calibration interval or not by using an SOC-OCV table lookup method, and calibrating only the battery cells with the voltage values in the allowable calibration interval. The preset time may be 2 hours, and the allowable calibration interval may be 2.7-3.2V. The SOC-OCV lookup table is a method by which the SOC and the cell voltage can be converted from each other through the mapping relationship of the SOC and the cell voltage. For example, a cell voltage of 2.7-3.2V may be expressed as a cell SOC of 0-30%. The battery cell SOC is 30-95% of the battery cell SOC in a platform period, and voltages corresponding to the battery cell SOC in the platform period can be the same.

Step 102: and when the battery cell SOC difference is larger than an equalization threshold value, carrying out lowest SOC equalization.

In the method of the embodiment, whether the SOC difference of the battery cells is larger than a preset electric quantity is determined, and if so, the lowest SOC equalization is performed. Wherein the preset amount of electricity may be set to 3%.

In the method of this embodiment, after performing the minimum SOC equalization, whether the minimum SOC equalization needs to be performed again may be determined according to the completion time of the minimum SOC equalization, the first preset days, the battery core SOC, the battery module SOC, the preset module electric quantity, and the self-discharge threshold.

As an alternative method, whether the lowest SOC equalization is needed again is judged according to the last lowest SOC equalization completion time and the battery module SOC, that is, self-discharge diagnosis is performed according to the self-discharge condition of the battery cells, so that the problem of poor capacity of the battery box caused by inconsistent self-discharge of each battery cell is solved. The method specifically comprises the step of judging whether the last lowest SOC balance completion time of the current time distance exceeds a first preset number of days. If so, acquiring the battery module SOC, and judging whether the lowest SOC equalization is needed again according to the battery module SOC, the preset module electric quantity, the battery core SOC and the self-discharge threshold value. If not, the average SOC equalization is selected. The first preset number of days may be 90 days.

In the method of this embodiment, whether the lowest SOC equalization needs to be performed again is determined according to the battery module SOC, the preset module power, the battery core SOC, and the self-discharge threshold, and specifically, the difference between the lowest battery module SOC and the highest battery module SOC in the battery module SOC of each battery module in the battery box may be obtained as the module SOC difference. Judging whether the module SOC difference is larger than the preset module electric quantity. If so, judging whether the lowest SOC balance is needed to be carried out again according to the battery cell SOC difference and the self-discharge threshold value. If not, the lowest SOC equalization is performed again. The preset module electric quantity can be set to 5%, and the self-discharge threshold value can be set to 8%.

In the method of this embodiment, the reference SOC is selected according to the battery cell SOC difference and the self-discharge threshold, specifically, whether the battery cell SOC difference is greater than the self-discharge threshold may be determined, if so, average SOC equalization is performed, and if not, whether the battery cell SOC difference is greater than the preset electric quantity may be continuously determined.

In the method of this embodiment, if the SOC difference of the battery cells is greater than the preset electric quantity, the lowest SOC is again equalized, otherwise, the average SOC is equalized.

Step 103: after the lowest SOC equalization is completed, carrying out average SOC equalization; and the average SOC is the average value of the battery core SOC of each battery core in the battery box.

In the method of the present embodiment, the lowest SOC is set as the reference SOC when the lowest SOC equalization is performed, and the average SOC is set as the reference SOC when the average SOC equalization is performed. As an alternative method, the difference between the cell SOC of the cell to be balanced and the reference SOC is obtained as the amount of power to be balanced. And the battery cells to be balanced are battery cells in the battery box, and the difference between the battery cell SOC and the reference SOC is larger than the preset electric quantity. And controlling the equalization current and the equalization time according to the electric quantity to be equalized so as to perform reference SOC equalization on the electric core to be equalized.

In the method described in the present embodiment, as an alternative method, there is a balanced abnormality protection condition. Specifically, when the electric quantity to be balanced is 0, the SOC balance is stopped. And stopping SOC equalization when the on-board temperature is greater than the maximum allowable temperature. And stopping carrying out SOC equalization on the battery cells to be equalized when the battery cell SOC of the battery cells to be equalized is lower than the discharge cut-off electric quantity.

In the method of this embodiment, the start time of the lowest SOC equalization is recorded, and it is determined whether the current time distance from the start time exceeds a second preset number of days. If so, stopping performing SOC equalization on the battery cells to be equalized, and if not, stopping performing SOC equalization on the battery cells to be equalized until the difference between the battery cell SOC of the battery cells to be equalized and the lowest SOC is smaller than or equal to the preset electric quantity. Wherein the second preset number of days may be 15 days. For example, when the lowest SOC balance is started for 90 days, the SOC balance is automatically stopped, and SOC balance is performed for 90 days until no battery cells need to be balanced. As an alternative method, parameters such as start time and finish time of SOC equalization need to be recorded each time the lowest SOC equalization or the average SOC equalization is performed, so as to perform query and judgment.

In the method of this embodiment, as an alternative method, after SOC equalization is performed on the to-be-equalized battery cell, the battery box may be further charged. Specifically, when the battery cell SOC in the battery box is lower than the undervoltage power-on SOC or the battery cell voltage in the battery box is lower than the discharge cut-off voltage, the battery box is charged. And stopping charging the battery box when the battery cell SOC in the battery box is higher than the discharge cut-off SOC. And when the lowest cell voltage in the cell voltages of each cell is larger than the plateau voltage in the cell box, stopping charging the cell box.

According to the method, the reference SOC can be automatically selected as the target electric quantity for balancing according to the condition that the electric quantity of the electric core in the battery module is inconsistent, wherein the reference SOC has the lowest SOC and the average SOC which are selectable, the balancing type is more changeable, and various conditions during SOC balancing can be more accurately adapted. The problem of system capacity attenuation caused by single-cell SOC abnormality or module inconsistency is solved. Meanwhile, whether the battery box needs to be started again for lowest SOC balance is judged according to self-discharge diagnosis, so that the problem of poor system capacity caused by inconsistent self-discharge conditions of all battery cells is solved. In addition, the SOC equalization can be directly carried out on the single battery cells to be equalized according to the reference SOC, so that the capacities of all the single battery cells are consistent, one-to-one operation is not needed, the process is simple and convenient, and the efficiency is higher.

Embodiment two: the application discloses another method for balancing the state of charge of the battery core, and referring to fig. 2, the method in this embodiment describes the whole process of selecting the reference SOC.

Step 201: and judging whether the SOC difference of the power core is larger than a preset electric quantity or not. If yes, the lowest SOC equalization is performed, and step 202 is performed. If not, the average SOC equalization is performed.

Step 202: and judging whether the current time is more than a first preset number of days from the lowest SOC balance completion time. If yes, go to step 203. If not, the average SOC equalization is performed.

Step 203: judging whether the module SOC difference is larger than the preset module electric quantity. If yes, go to step 204. If not, the lowest SOC equalization is performed.

Step 204: and judging whether the power core SOC difference is larger than the self-discharge threshold value. If yes, average SOC equalization is performed. If not, go to step 205.

Step 205: and judging whether the SOC difference of the power core is larger than the preset electric quantity or not. If yes, the lowest SOC equalization is performed. If not, the average SOC equalization is performed.

The method of the embodiment introduces the whole process of selecting the reference SOC, can automatically select the lowest SOC or the average SOC as the target electric quantity for balancing aiming at the condition that the electric quantity of the battery cells in the battery module is inconsistent, has more changeable balancing types, and can be more accurately adapted to various conditions during the SOC balancing.

Embodiment III: referring to fig. 3, the method in this embodiment is described with respect to the power-up operation after SOC equalization.

Step 301: and when the battery cell SOC in the battery box is lower than the undervoltage power-supplementing SOC or the battery cell voltage in the battery box is lower than the discharge cut-off voltage, charging the battery box.

Step 302: and stopping charging the battery box when the battery cell SOC in the battery box is higher than the discharge cut-off SOC.

In the method described in this embodiment, the battery box is not allowed to discharge at this time.

Step 303: and stopping charging the battery box when the lowest cell voltage in the cell voltages of each cell is larger than the plateau voltage.

In the method described in this embodiment, the battery box is not allowed to discharge at this time. As an alternative method, the battery box is allowed to charge when the accumulated charge capacity reaches the charge threshold. The charging threshold may be 0.01 x the total power of the battery box.

The method of the embodiment is described with respect to the balanced power-up operation. After the equalization of the SOC is finished, the system is charged when the SOC of all the battery cells in the battery box is consistent, and the problem of system capacity attenuation caused by abnormal capacity of the single battery cells or inconsistent modules can be solved.

Based on the method for equalizing the state of charge of the battery cells disclosed in the above embodiment, the present embodiment correspondingly discloses a device for equalizing the state of charge of the battery cells. Referring to fig. 4, the apparatus for equalizing the state of charge of the battery cells includes: a difference value acquisition unit 401, a threshold value judgment unit 402, and an equalization unit 403;

the difference value obtaining unit 401 is configured to obtain, as a difference between the battery cell SOC, a difference between the lowest SOC and the highest SOC in the battery cell SOC of each battery cell in the battery box;

the threshold value judging unit 402 is configured to perform lowest SOC equalization when the battery cell SOC difference is greater than an equalization threshold value;

the equalization unit 403 is configured to perform average SOC equalization after the lowest SOC equalization is completed; and the average SOC is the average value of the battery core SOC of each battery core in the battery box.

Optionally, the apparatus further includes:

and the equalization judging unit is used for judging whether the lowest SOC equalization is needed to be performed again according to the completion time of the lowest SOC equalization, the first preset days, the battery core SOC, the battery module SOC, the preset module electric quantity and the self-discharge threshold value.

Optionally, the equalization judging unit includes:

the first judging subunit is configured to obtain the battery module SOC in the battery box if the current time is greater than the first preset number of days from the completion time, and judge whether minimum SOC equalization is needed again according to the battery module SOC, the preset module electric quantity, the battery core SOC and the self-discharge threshold;

and the first day number judging subunit is used for carrying out average SOC equalization if the current time is not longer than the first preset days from the completion time.

Optionally, the first judging subunit includes:

a difference value obtaining subunit, configured to obtain, as a module SOC difference, a difference between a lowest battery module SOC and a highest battery module SOC in the battery module SOC of each battery module in the battery box;

the second judging subunit is used for judging whether the lowest SOC equalization is needed again according to the battery cell SOC difference and the self-discharge threshold value when the module SOC difference is larger than the preset module electric quantity;

and the module electric quantity judging subunit is used for carrying out lowest SOC equalization again when the module SOC difference is smaller than or equal to the preset module electric quantity.

Optionally, the second judging subunit includes:

a discharge threshold judging subunit, configured to perform average SOC equalization when the battery cell SOC difference is greater than the self-discharge threshold;

the electric quantity judging subunit is used for judging whether the electric core SOC difference is larger than the preset electric quantity or not when the electric core SOC difference is smaller than or equal to the self-discharge threshold value;

a lowest equalization subunit, configured to perform lowest SOC equalization again;

and the average equalization subunit is used for carrying out average SOC equalization.

Optionally, the equalizing unit 403 includes:

a lowest reference subunit, configured to take a lowest SOC as a reference SOC when performing lowest SOC equalization;

an average reference subunit, configured to take the average SOC as a reference SOC when performing average SOC equalization;

the electric quantity to be balanced obtaining subunit is used for obtaining the difference between the battery cell SOC of the battery cell to be balanced and the reference SOC as the electric quantity to be balanced; the battery cell to be balanced is in the battery box, and the difference between the battery cell SOC and the reference SOC is larger than the preset electric quantity;

and the reference equalization subunit is used for controlling equalization current and equalization duration according to the electric quantity to be equalized so as to perform reference SOC equalization on the electric core to be equalized.

Optionally, the reference equalization subunit includes:

the electric quantity to be balanced judging subunit is used for stopping carrying out reference SOC balance on the electric core to be balanced when the electric quantity to be balanced is 0;

the temperature judging subunit is used for stopping carrying out reference SOC equalization on the battery cells to be equalized when the on-board temperature is greater than the maximum allowable temperature;

and the power cut-off judging subunit is used for stopping carrying out reference SOC equalization on the battery cells to be equalized when the battery cell SOC of the battery cells to be equalized is lower than the discharge power cut-off.

Optionally, the threshold value judging unit 402 includes:

a time recording subunit, configured to record the start time of the lowest SOC equalization;

a second day judging subunit, configured to judge whether the current time is greater than a second preset day from the opening time;

a stop equalization subunit configured to stop performing the lowest SOC equalization;

and stopping the lowest SOC equalization until the difference of the battery cell SOCs is smaller than or equal to the preset electric quantity.

Optionally, the apparatus further includes:

the under-voltage power-up judging subunit is used for charging the battery box when the SOC of the battery cell in the battery box is lower than the under-voltage power-up SOC or the voltage of the battery cell in the battery box is lower than the discharge cut-off voltage;

a discharge cut-off judging subunit, configured to stop charging the battery box when the SOC of the battery cell in the battery box is higher than the discharge cut-off SOC;

and the platform-stage voltage judging subunit is used for stopping charging the battery box when the lowest cell voltage in the cell voltages of each cell is larger than the platform-stage voltage.

The embodiments in this specification are described in a progressive manner. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.

It is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

The features described in the embodiments of the present specification may be interchanged or combined to enable those skilled in the art to make or use the present application.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (18)

1. A method for equalizing the state of charge of cells, wherein at least one battery module is contained in a battery box, and each battery module contains at least one cell, the method comprising:

acquiring the difference between the lowest SOC and the highest SOC in the battery core SOC of each battery core in the battery box as the battery core SOC difference;

when the SOC difference of the battery cells is larger than an equalization threshold value, carrying out lowest SOC equalization;

after the lowest SOC equalization is completed, carrying out average SOC equalization; and the average SOC is the average value of the battery core SOC of each battery core in the battery box.

2. The method of claim 1, wherein after performing the minimum SOC equalization, the method further comprises:

and judging whether the lowest SOC equalization is needed again according to the completion time of the lowest SOC equalization, the first preset days, the battery cell SOC, the battery module SOC, the preset module electric quantity and the self-discharge threshold value.

3. The method of claim 2, wherein the determining whether the minimum SOC equalization is needed again according to the completion time of the minimum SOC equalization, the first preset number of days, the battery cell SOC, the battery module SOC, the preset module power, and the self-discharge threshold value comprises:

if the current time is longer than the completion time by the first preset number of days, acquiring a battery module SOC in the battery box, and judging whether minimum SOC equalization is needed again according to the battery module SOC, the preset module electric quantity, the battery core SOC and the self-discharge threshold;

and if the current time is not longer than the completion time by the first preset days, carrying out average SOC equalization.

4. The method of claim 3, wherein the determining whether the minimum SOC equalization is needed again based on the battery module SOC, the preset module power, the battery cell SOC, and the self-discharge threshold comprises:

obtaining the difference between the lowest battery module SOC and the highest battery module SOC in the battery module SOC of each battery module in the battery box as a module SOC difference;

when the module SOC difference is larger than the preset module electric quantity, judging whether the lowest SOC equalization is needed to be performed again according to the battery cell SOC difference and the self-discharge threshold value;

and when the module SOC difference is smaller than or equal to the preset module electric quantity, carrying out lowest SOC equalization again.

5. The method of claim 4, wherein the determining whether the lowest SOC equalization is needed again based on the cell SOC difference and the self-discharge threshold comprises:

when the battery cell SOC difference is larger than the self-discharge threshold value, carrying out average SOC equalization;

when the battery cell SOC difference is smaller than or equal to the self-discharge threshold value, judging whether the battery cell SOC difference is larger than the preset electric quantity or not;

if yes, carrying out the lowest SOC balance again;

if not, the average SOC equalization is performed.

6. The method of claim 1, wherein performing a minimum SOC equalization or an average SOC equalization comprises:

when the lowest SOC is balanced, taking the lowest SOC as a reference SOC;

when average SOC equalization is performed, taking the average SOC as a reference SOC;

acquiring the difference between the battery cell SOC of the battery cell to be balanced and the reference SOC as the electric quantity to be balanced; the battery cell to be balanced is in the battery box, and the difference between the battery cell SOC and the reference SOC is larger than the preset electric quantity;

and controlling the equalization current and the equalization time according to the electric quantity to be equalized so as to perform reference SOC equalization on the electric core to be equalized.

7. The method of claim 6, wherein performing reference SOC equalization comprises:

when the electric quantity to be balanced is 0, stopping carrying out reference SOC balance on the electric core to be balanced;

when the on-board temperature is greater than the maximum allowable temperature, stopping performing reference SOC equalization on the battery cells to be equalized;

and stopping carrying out reference SOC equalization on the battery cells to be equalized when the battery cell SOC of the battery cells to be equalized is lower than the discharge cut-off electric quantity.

8. The method of any of claims 1-5, wherein performing minimum SOC equalization comprises:

recording the start time of the lowest SOC balance;

judging whether the current time is more than a second preset number of days from the starting time;

if yes, stopping carrying out the lowest SOC balance;

if not, stopping balancing the lowest SOC until the difference of the battery core SOCs is smaller than or equal to the preset electric quantity.

9. The method according to claim 6 or 7, characterized in that after reference SOC equalization, the method further comprises:

when the battery cell SOC in the battery box is lower than the undervoltage power-on SOC or the battery cell voltage in the battery box is lower than the discharge cut-off voltage, charging the battery box;

when the SOC of the battery cell in the battery box is higher than the discharge cut-off SOC, stopping charging the battery box;

and stopping charging the battery box when the lowest cell voltage in the cell voltages of each cell is larger than the plateau voltage.

10. An apparatus for equalizing state of charge of a cell, comprising: the device comprises a difference value acquisition unit, a threshold value judgment unit and an equalization unit;

the difference value acquisition unit is used for acquiring the difference between the lowest SOC and the highest SOC in the battery core SOC of each battery core in the battery box as the battery core SOC difference;

the threshold value judging unit is used for carrying out lowest SOC equalization when the battery cell SOC difference is larger than an equalization threshold value;

the balancing unit is used for carrying out average SOC balancing after the lowest SOC balancing is completed; and the average SOC is the average value of the battery core SOC of each battery core in the battery box.

11. The apparatus of claim 10, wherein the apparatus further comprises:

and the equalization judging unit is used for judging whether the lowest SOC equalization is needed to be performed again according to the completion time of the lowest SOC equalization, the first preset days, the battery core SOC, the battery module SOC, the preset module electric quantity and the self-discharge threshold value.

12. The apparatus according to claim 11, wherein the equalization judging unit includes:

the first judging subunit is configured to obtain the battery module SOC in the battery box if the current time is greater than the first preset number of days from the completion time, and judge whether minimum SOC equalization is needed again according to the battery module SOC, the preset module electric quantity, the battery core SOC and the self-discharge threshold;

and the first day number judging subunit is used for carrying out average SOC equalization if the current time is not longer than the first preset days from the completion time.

13. The apparatus of claim 12, wherein the first determination subunit comprises:

a difference value obtaining subunit, configured to obtain, as a module SOC difference, a difference between a lowest battery module SOC and a highest battery module SOC in the battery module SOC of each battery module in the battery box;

the second judging subunit is used for judging whether the lowest SOC equalization is needed again according to the battery cell SOC difference and the self-discharge threshold value when the module SOC difference is larger than the preset module electric quantity;

and the module electric quantity judging subunit is used for carrying out lowest SOC equalization again when the module SOC difference is smaller than or equal to the preset module electric quantity.

14. The apparatus of claim 13, wherein the second determination subunit comprises:

a discharge threshold judging subunit, configured to perform average SOC equalization when the battery cell SOC difference is greater than the self-discharge threshold;

the electric quantity judging subunit is used for judging whether the electric core SOC difference is larger than the preset electric quantity or not when the electric core SOC difference is smaller than or equal to the self-discharge threshold value;

a lowest equalization subunit, configured to perform lowest SOC equalization again;

and the average equalization subunit is used for carrying out average SOC equalization.

15. The apparatus of claim 10, wherein the equalization unit comprises:

a lowest reference subunit, configured to take a lowest SOC as a reference SOC when performing lowest SOC equalization;

an average reference subunit, configured to take the average SOC as a reference SOC when performing average SOC equalization;

the electric quantity to be balanced obtaining subunit is used for obtaining the difference between the battery cell SOC of the battery cell to be balanced and the reference SOC as the electric quantity to be balanced; the battery cell to be balanced is in the battery box, and the difference between the battery cell SOC and the reference SOC is larger than the preset electric quantity;

and the reference equalization subunit is used for controlling equalization current and equalization duration according to the electric quantity to be equalized so as to perform reference SOC equalization on the electric core to be equalized.

16. The apparatus of claim 15, wherein the reference equalization subunit comprises:

the electric quantity to be balanced judging subunit is used for stopping carrying out reference SOC balance on the electric core to be balanced when the electric quantity to be balanced is 0;

the temperature judging subunit is used for stopping carrying out reference SOC equalization on the battery cells to be equalized when the on-board temperature is greater than the maximum allowable temperature;

and the power cut-off judging subunit is used for stopping carrying out reference SOC equalization on the battery cells to be equalized when the battery cell SOC of the battery cells to be equalized is lower than the discharge power cut-off.

17. The apparatus according to any one of claims 10 to 14, wherein the threshold value judging unit includes:

a time recording subunit, configured to record the start time of the lowest SOC equalization;

a second day judging subunit, configured to judge whether the current time is greater than a second preset day from the opening time;

a stop equalization subunit configured to stop performing the lowest SOC equalization;

and stopping the lowest SOC equalization until the difference of the battery cell SOCs is smaller than or equal to the preset electric quantity.

18. The apparatus according to claim 15 or 16, characterized in that the apparatus further comprises:

the under-voltage power-up judging subunit is used for charging the battery box when the SOC of the battery cell in the battery box is lower than the under-voltage power-up SOC or the voltage of the battery cell in the battery box is lower than the discharge cut-off voltage;

a discharge cut-off judging subunit, configured to stop charging the battery box when the SOC of the battery cell in the battery box is higher than the discharge cut-off SOC;

and the platform-stage voltage judging subunit is used for stopping charging the battery box when the lowest cell voltage in the cell voltages of each cell is larger than the platform-stage voltage.