WO2023082794A1

WO2023082794A1 - Battery cell equalization method for battery pack

Info

Publication number: WO2023082794A1
Application number: PCT/CN2022/116963
Authority: WO
Inventors: 李强; 汤殷霞; 侯森; 宋中奇
Original assignee: 联合汽车电子有限公司
Priority date: 2021-11-09
Filing date: 2022-09-05
Publication date: 2023-05-19
Also published as: CN114069781A

Abstract

Provided in the present invention is a battery cell equalization method for a battery pack. The method comprises: when a processor goes into hibernation, determining whether a battery cell of a battery pack needs to be equalized; and when it is determined that the battery cell needs to be equalized, performing offline equalization on the battery cell when the processor is hibernating. By means of the present invention, offline equalization is performed on a battery cell of a battery pack by utilizing the hibernation time of a processor, such that the problem of it being impossible to complete battery cell equalization due to an insufficient online equalization time of a large-capacity battery pack or a battery pack having a very large self-discharge rate is solved, thereby prolonging the service life of the battery cell, and improving the energy utilization efficiency of the battery pack.

Description

Cell equalization method for battery packs

technical field

The invention relates to the technical field of new energy batteries, in particular to a cell equalization method for a battery pack.

Background technique

The battery pack of a new energy vehicle is used to provide driving power for the entire vehicle. The battery pack is usually composed of multiple battery modules connected in series, and each battery module contains multiple batteries. When the battery cell fails, such as overtemperature, overvoltage or undervoltage, the thermal runaway of the battery pack may occur, resulting in accidents such as combustion, explosion, and personal injury. The battery pack has a built-in battery management system (Battery Management System, BMS). The battery management system uses the sampling chip to continuously monitor the status of the battery cells in real time, and can detect battery failures in time and take corresponding measures, such as alarming, limiting power, and downtime. High voltage, heat dissipation of the battery cell and anti-explosion, etc.

During the use of the battery pack, due to the difference in the self-discharge rate of the battery cell and the aging speed of the battery cell, there will be differences between the cells. If the battery pack is used in a harsh environment, the imbalance between the cells will be worsened. Therefore, during the use of the battery pack, it is necessary to balance the cells to solve the problem of inconsistent electric energy between the cells, so as to improve the energy utilization efficiency of the battery pack, increase the service life of the battery pack, and improve the endurance of new energy vehicles. As the cruising range of the vehicle becomes longer and longer, the capacity of the battery cell is also increasing, and the capacity of the battery cell that needs to be balanced is also increasing.

At present, the equalization method is mainly realized through passive equalization, that is, an equalization channel is designed in the sampling chip. When the equalization channel is turned on, the electric energy of the battery cells can be consumed, and the electric energy of the high-energy electric cells is reduced to achieve equalization among the electric cells. The speed of cell equalization is proportional to the equalization current and inversely proportional to the equalization time. Due to the limitation of the heat dissipation capacity of the battery management system and the chip temperature protection, the equalization current cannot be too large, so a longer equalization time is required. However, due to the The average running time of the vehicle is limited every day, and the online time of the processor is generally 2 hours to 5 hours on average. For batteries with large capacity and high self-discharge rate, this time cannot complete the balance of the batteries, resulting in battery failure. The core life is shortened, and the energy utilization efficiency of the battery pack is not high.

Contents of the invention

The object of the present invention is to provide a cell equalization method for a battery pack to solve the problems of insufficient online cell equalization time, resulting in shortened cell life and low energy utilization efficiency of the battery pack.

In order to achieve the above object, the present invention provides a cell equalization method for a battery pack, comprising:

When the processor enters sleep mode, it is judged whether the cells of the battery pack need to be balanced; and,

When it is determined that the battery cell needs to be balanced, offline balancing is performed on the battery cell after the processor sleeps.

Optionally, when it is determined that the battery pack needs to be balanced, obtain a target balanced voltage, and when the voltage of the battery cell reaches the target balanced voltage, stop performing offline balancing on the battery cell; or,

When it is determined that the battery pack needs to be balanced, obtain the remaining balancing time of each of the cells, and stop performing offline balancing on the cells when the offline balancing time of the cells reaches the corresponding remaining balancing time ;or,

When it is determined that the battery pack requires equalization, the target equalization voltage and the remaining equalization time of each battery cell are obtained, and when the voltage of the battery cell reaches the target equalization voltage and/or the battery cell performs When the offline equalization time reaches the corresponding remaining equalization time, the off-line equalization of the cells is stopped.

Optionally, the target equalization voltage is the voltage of the cell with the smallest capacity in the battery pack.

Optionally, several sampling chips are used to perform off-line equalization on the cells in the battery pack, each of the sampling chips has multiple equalization channels, and one equalization channel is used to perform off-line equalization on one of the cells.

Optionally, all the equalization channels of each sampling chip are turned on synchronously, so that the cells can be balanced offline synchronously.

Optionally, the equalization channels in the sampling chip are arranged in sequence according to serial numbers, and the equalization channels with odd numbers are turned on synchronously, so that the cells corresponding to the equalization channels with odd numbers can perform offline equalization synchronously; The even-numbered equalization channels are turned on synchronously, so that the cells corresponding to the even-numbered equalization channels perform offline equalization synchronously.

Optionally, when performing offline equalization on the cells, first open the equalization channel with an odd number, and after the cells corresponding to the equalization channel with an odd number have completed offline equalization, open all the equalization channels with an even number. The above-mentioned equalization channels, until the batteries corresponding to the equalization channels with even serial numbers have completed offline equalization; or,

When performing offline equalization on the cells, first open the equalization channel with an even number, and after the cells corresponding to the equalization channel with an even number have completed offline equalization, open the equalization channel with an odd number, Off-line equalization is completed for the cells corresponding to the equalization channel whose serial number is odd.

Optionally, when performing offline equalization on the cells, alternately open the equalization channel with an even number and the equalization channel with an odd number until all the cells are off-line equalized.

Optionally, when performing offline equalization on the battery core, the sampling chip monitors its own temperature in real time, and when the temperature of any of the sampling chips is greater than a set temperature value, all the equalization channels are closed to stop Perform off-line equalization on all the cells.

Optionally, when performing offline balancing on the battery cells, the processor is woken up every set time, and after the processor is woken up, it detects whether the battery pack fails online, and when the battery pack is detected When no fault occurs, the processor goes to sleep.

Optionally, the failure of the battery pack includes a disconnection failure of the communication line between the sampling chip and the battery cell, an overvoltage/undervoltage/overtemperature failure of the battery cell, a failure of the sampling chip One or more of the failure of the equalization channel, the overtemperature failure of the sampling chip and the failure of the temperature sensor in the battery pack.

In the cell equalization method of the battery pack provided by the present invention, when the processor enters sleep mode, it is judged whether the cells of the battery pack need to be balanced; Off-line equalization of the above-mentioned cells. The present invention uses the sleep time of the processor to perform off-line equalization on the battery cells of the battery pack, which can solve the problem that the online equalization time of a large-capacity battery pack or a battery pack with a high self-discharge rate is not enough to complete the battery cell equalization. The life of the battery cell and the energy utilization efficiency of the battery pack are improved.

Description of drawings

FIG. 1 is a flow chart of a cell equalization method for a battery pack provided by an embodiment of the present invention;

FIG. 2 is another flow chart of the cell equalization method for a battery pack provided by an embodiment of the present invention.

Detailed ways

The specific implementation manner of the present invention will be described in more detail below with reference to schematic diagrams. The advantages and features of the present invention will be more apparent from the following description. It should be noted that all the drawings are in very simplified form and use inaccurate scales, and are only used to facilitate and clearly assist the purpose of illustrating the embodiments of the present invention.

FIG. 1 is a flow chart of the cell equalization method for a battery pack provided in this embodiment. As shown in Figure 1, the cell equalization method of the battery pack provided in this embodiment includes:

Step S100: When the processor enters sleep mode, determine whether the cells of the battery pack need to be balanced; and,

Step S200: When it is determined that the battery cell needs to be balanced, perform offline balancing on the battery cell after the processor sleeps.

In this embodiment, the battery pack is a battery pack of a new energy vehicle, but it should not be limited thereto. There is a battery management system (BMS) in the battery pack, and the battery management system includes a processor, a bridge chip and several sampling chips, and the bridge chip is connected to the sampling chips one by one in the form of a daisy chain, or the bridge chip The chip can also be connected with several sampling chips to form a circular daisy chain. The sampling chip can be any known sampling chip, such as an analog front end sampling chip (Analog Front End, AFE), and one sampling chip can correspond to monitor the battery cells in a battery module of the battery pack. state, the sampling chip will send the collected signals such as cell voltage and temperature to the bridge chip through the daisy chain, and the bridge chip will forward all the signals collected by the sampling chip to the processor for processing. deal with.

FIG. 2 is another flow chart of the cell equalization method for the battery pack provided in this embodiment. As shown in FIG. 2 , step S100 is executed. After the processor is powered off, it will go into sleep mode. When the processor is powered off, the processor will determine whether the battery cells need to be balanced. Optionally, the processor may control the sampling chip to collect the voltage of the batteries, and judge whether the batteries need to be balanced according to the voltage difference between the batteries, for example, the voltage in the batteries The voltage difference between the lowest battery cell and the highest voltage battery cell reaches a set voltage value (for example, 0.1V), and it can be determined whether the battery cells need to be balanced accordingly.

Execute step S200, when it is determined that the battery needs to be balanced, perform offline balancing on the battery after the processor sleeps, so as to use the sleep time of the processor to perform offline balancing on the battery, which can solve the problem Large-capacity battery packs or battery packs with a high self-discharge rate do not have enough online equalization time to complete the cell equalization problem, which improves the life of the battery cells and the energy utilization efficiency of the battery pack.

Further, when it is determined that the cells need to be balanced, the processor will also obtain the remaining equalization time corresponding to each of the cells. When the off-line equalization time of the cell reaches the corresponding remaining equalization time, it indicates that the cell has been balanced, and at this time, the off-line equalization of the cell can be stopped.

It should be understood that since the remaining power of each of the batteries may be the same or different, the remaining equalization time corresponding to each of the batteries may also be the same or different. The times can also be the same or different.

As an optional embodiment, when it is determined that the battery cells need to be balanced, the processor may also obtain a target balanced voltage, and the target balanced voltage may be a voltage of a battery cell with the lowest voltage among the battery cells. When the voltage of the battery cell reaches the target balancing voltage, it indicates that the battery cell has been balanced, and at this time, the offline balancing of the battery cell can be stopped.

As an optional embodiment, when it is determined that the cells need to be balanced, the processor may also acquire both the remaining equalization time corresponding to each of the cells and the target equalization voltage, when the voltage of the cells When the target equalization voltage is reached and/or the off-line equalization time of the cells reaches the corresponding remaining equalization time, it indicates that the cells have completed equalization, and at this time, the off-line equalization of the cells can be stopped.

Further, the sampling chip has a plurality of sampling channels and a plurality of equalization channels. When the sampling channel is turned on, the sampling chip can collect the cell voltage and cell temperature of a plurality of the cells. Usually, one The sampling channel is used to collect the voltage of one cell or the temperature of one cell; when the equalization channel is turned on, the sampling chip can equalize a plurality of the cells. Usually, one equalization channel is used for Perform balancing (off-line balancing or online balancing) on one of the cells. Therefore, whether to balance the cell depends on whether the sampling chip enables the equalization channel.

Based on this, when it is determined that the cells need to be balanced, all the equalization channels of each sampling chip can be turned on synchronously, so that the cells can be balanced offline synchronously. Gradually turn off the equalization channel. Since the batteries are balanced offline synchronously, the time for offline balancing can be saved, and the balancing efficiency of the batteries can be improved.

Further, the equalization channels in the sampling chip are usually arranged in order according to the serial number. In order to prevent the adjacent equalization channels from interfering with each other when they are turned on, the equalization channels with odd numbers can be turned on synchronously, so that the serial numbers The cells corresponding to the odd-numbered equalization channels perform offline equalization synchronously; the even-numbered equalization channels can be turned on synchronously, so that the cells corresponding to the even-numbered equalization channels perform offline equalization synchronously. It should be understood that the equalization channel with an odd number and the equalization channel with an even number are not turned on at the same time, that is, when the equalization channel with an even number is turned on, the circuit corresponding to the equalization channel with an even number The cell is performing offline equalization. At this time, the equalization channel with an odd number is closed, and the cell corresponding to the equalization channel with an odd number is not performing offline equalization; otherwise, when the equalization channel with an odd number is turned on , the cell corresponding to the equalization channel with an odd number is performing offline equalization, at this time, the equalization channel with an even number is closed, and the cell corresponding to the equalization channel with an even number is not performing offline equalization .

For example, there are four equalization channels, the serial numbers are 1, 2, 3, and 4 respectively, and the four equalization channels with serial numbers 1, 2, 3, and 4 are arranged in sequence, wherein, the serial numbers are 1, 3 The two equalization channels are opened synchronously, and the two equalization channels whose serial numbers are 2 and 4 are opened synchronously; The equalization channel is closed, and when the two equalization channels with sequence numbers 2 and 4 are turned on, the two equalization channels with sequence numbers 1 and 3 are closed.

As an optional embodiment, when performing offline equalization on the cells of the battery pack, the equalization channel with an odd number can be opened first, and after the cells corresponding to the equalization channel with an odd number have completed offline equalization, Then open the equalization channel with an even number until the cells corresponding to the equalization channel with an even number complete off-line equalization. Of course, when performing offline equalization on the battery cells of the battery pack, all the equalization channels with even serial numbers can also be opened first, and after the batteries corresponding to all the equalization channels with even serial numbers have completed offline equalization, then Turn on all the equalization channels with odd numbers until the cells corresponding to all the equalization channels with odd numbers complete off-line equalization.

As an optional embodiment, when performing offline equalization on the cells of the battery pack, the equalization channel with an even number and the equalization channel with an odd number can be alternately opened until all the cells are offline. balanced. It is equivalent to alternately performing offline equalization on the cells corresponding to the equalization channel with an even number and the cells corresponding to the equalization channel with an odd number, and the cells corresponding to the equalization channel with an even number and the cells with an odd number The battery cells corresponding to the equalization channel have little difference in the voltage drop each time, which is beneficial to increase the stability of the battery cell balance.

Furthermore, since the processor is dormant when performing offline balancing on the battery cells, it is impossible to monitor the state of the battery cells in real time and take corresponding measures according to the state of the battery cells, the battery pack has potential safety hazards .

Based on this, in this embodiment, when performing offline equalization on the cells of the battery pack, the sampling chip monitors its own temperature in real time. Since the temperature of the equalization channel can be approximately equal to the temperature of the sampling chip, when detecting When the temperature of any of the sampling chips is greater than a set temperature value, all the equalization channels are closed to stop off-line equalization of all the cells, so as to ensure the safety of the battery pack.

Further, in this embodiment, when performing offline balancing on the battery cells, the processor is woken up every set time, and after the processor is woken up, it detects whether the battery pack fails online. When the processor detects that the battery pack is faulty, since the processor is online at this time, it can take corresponding actions for these faults to ensure the safety of the battery pack. In the event of failure, the processor can go into sleep mode again, and perform off-line balancing on the cells when necessary.

It can be understood that whether the failure of the battery pack includes a disconnection failure of the communication line between the sampling chip and the battery cell, an overvoltage/undervoltage/overtemperature failure of the battery cell, the One or more of the failure of the equalization channel of the sampling chip, the overtemperature failure of the sampling chip, and the failure of the temperature sensor in the battery pack, but not limited thereto.

To sum up, in the cell equalization method of the battery pack provided by the embodiment of the present invention, when the processor enters sleep mode, it is judged whether the cells of the battery pack need to be balanced; Offline balancing is performed on the battery cells when the device is in sleep mode. The present invention uses the sleep time of the processor to perform off-line equalization on the battery cells of the battery pack, which can solve the problem that the online equalization time of a large-capacity battery pack or a battery pack with a high self-discharge rate is not enough to complete the battery cell equalization. The life of the battery cell and the energy utilization efficiency of the battery pack are improved.

It should be noted that each embodiment in this specification is described in a progressive manner, each embodiment focuses on the differences from other embodiments, and the same and similar parts of each embodiment can be referred to each other. As for the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and for relevant information, please refer to the description of the method part.

It should also be noted that although the present invention has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or be modified to be equivalent to equivalent changes. Example. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention, which do not deviate from the content of the technical solution of the present invention, still belong to the scope of protection of the technical solution of the present invention.

It should also be understood that, unless otherwise specified or pointed out, the terms “first”, “second”, “third” and other descriptions in the specification are only used to distinguish each component, element, step, etc. in the specification, rather than It is used to express the logical relationship or sequence relationship between various components, elements, and steps.

In addition, it should be understood that the terminology described herein is used to describe particular embodiments only and is not intended to limit the scope of the invention. It must be noted that as used herein and in the appended claims, the singular forms "a" and "an" include plural referents unless the context clearly dictates otherwise. For example, a reference to "a step" or "a means" means a reference to one or more steps or means, and may include sub-steps as well as sub-means. All conjunctions used should be understood in their broadest sense. And, the word "or" should be understood as having the definition of logical "or" rather than logical "exclusive or", unless the context clearly expresses the contrary meaning. Additionally, implementation of methods and/or apparatus in embodiments of the invention may include performing selected tasks manually, automatically, or in combination.

Claims

A cell equalization method for a battery pack, characterized in that it comprises:

When the processor enters sleep mode, it is judged whether the cells need to be balanced; and,

When it is determined that the battery cell needs to be balanced, offline balancing is performed on the battery cell after the processor sleeps.
The method for equalizing cells of a battery pack according to claim 1, wherein when it is determined that the cells of the battery pack need to be balanced, a target equalization voltage is obtained, and when the voltage of the cells reaches the target equalization voltage , stop performing offline balancing on the cell.
The cell equalization method of a battery pack according to claim 1, wherein when it is determined that the cells of the battery pack need to be balanced, the remaining equalization time of each of the cells is obtained, and when the cells are When the offline equalization time reaches the corresponding remaining equalization time, the off-line equalization of the cells is stopped.
The cell equalization method of the battery pack according to claim 1, wherein when it is determined that the cells of the battery pack need to be balanced, the target equalization voltage and the remaining equalization time of each of the cells are obtained, When the voltage of the cell reaches the target equalization voltage and/or the offline equalization time of the cell reaches a corresponding remaining equalization time, the off-line equalization of the cell is stopped.
The cell equalization method for a battery pack according to claim 2 or 4, wherein the target equalization voltage is the voltage of the cell with the smallest capacity in the battery pack.
The cell equalization method of a battery pack according to any one of claims 1-5, wherein several sampling chips are used to perform off-line equalization of the cells in the battery pack, and each of the sampling chips has multiple equalization channels, and each of the equalization channels is used to perform offline equalization on one of the cells.
The cell equalization method of a battery pack according to claim 6, wherein all the equalization channels of each sampling chip are turned on synchronously, so that the cells can be balanced offline synchronously.
The cell equalization method of a battery pack according to claim 6, wherein the equalization channels in the sampling chip are arranged in sequence according to serial numbers, and the equalization channels with odd serial numbers are opened synchronously so that the serial numbers are odd The cells corresponding to the equalization channels of the above-mentioned equalization channels perform offline equalization synchronously; the equalization channels with even numbers are synchronously turned on, so that the cells corresponding to the equalization channels with even number numbers perform offline equalization synchronously.
The cell equalization method of a battery pack according to claim 8, wherein when performing offline equalization on the cells, the equalization channel with an odd serial number is opened first, and when the equalization channel with an odd serial number corresponds to After all the cells have completed offline equalization, open the equalization channel with an even number until the cells corresponding to the equalization channel with an even number have completed offline equalization; or,

When performing offline equalization on the cells, first open the equalization channel with an even number, and after the cells corresponding to the equalization channel with an even number have completed offline equalization, open the equalization channel with an odd number, Off-line equalization is completed for the cells corresponding to the equalization channel whose serial number is odd.
The cell equalization method of a battery pack according to claim 8, wherein when performing offline equalization on the cells, alternately open the equalization channel with an even number and the equalization channel with an odd number until All of the cells are off-line balanced.
The cell equalization method of a battery pack according to claim 6, wherein when the cells are balanced offline, the sampling chip monitors its own temperature in real time, and when the temperature of any of the sampling chips is greater than a When setting the temperature value, all the equalization channels are closed to stop off-line equalization of all the cells.
The cell equalization method of a battery pack according to claim 6, wherein when the cells are balanced offline, the processor is woken up at intervals of a set time, and the processor is woken up for online detection Whether the battery pack is faulty, when it is detected that the battery pack is not faulty, the processor enters sleep mode.
The battery cell equalization method of a battery pack according to claim 12, wherein the failure of the battery pack includes a disconnection fault of the communication line between the sampling chip and the battery cell, One or more of over-voltage/under-voltage/over-temperature faults, a fault in the equalization channel of the sampling chip, an over-temperature fault in the sampling chip, and a fault in the temperature sensor in the battery pack.