CN109428130B

CN109428130B - Battery equalization method, system, vehicle, storage medium and electronic device

Info

Publication number: CN109428130B
Application number: CN201710775052.XA
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: 2020-09-15
Anticipated expiration: 2037-08-31
Also published as: CN109428130A

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 time change rate of each single battery in the battery pack; acquiring a reference time change rate required by balancing; determining a target equalization duration of the single battery to be equalized according to a time change rate of the single battery to be equalized in the battery pack, the reference time change rate and a preset equalization duty ratio, wherein the equalization duty ratio is a ratio of an equalization time period to a unit cycle in the unit cycle, and the unit cycle comprises the equalization time period and a sampling time period; and controlling the balance of the single battery to be balanced in the balancing time period of the unit cycle according to the target balancing duration.

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 is generally formed by connecting a plurality of single batteries in series to form a module. 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 difference between the single batteries may cause overcharge of some single batteries, over-discharge of some single batteries, affect the service life of the batteries, damage the batteries, and generate a large amount of heat to cause combustion or explosion of the batteries.

At present, balancing management is performed on a battery pack, battery information of each single battery in the battery pack is usually acquired in real time, whether the single battery needs balancing or not is determined according to the acquired battery information, and when the single battery needs balancing, balancing duration is further determined according to the battery information. However, in such a manner, equalization may be performed while acquiring battery information, and fluctuation of the battery information may be caused in the equalization process, which may cause inaccuracy of the acquired battery information, and further cause inaccuracy of the calculated equalization duration and poor equalization effect when a single battery needs equalization.

Disclosure of Invention

The method can separately perform sampling and equalization in a unit period, ensures the accuracy of acquired battery information, calculates the equalization duration accurately, and improves the equalization effect of a battery pack.

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

acquiring the time change rate of each single battery in the battery pack;

acquiring a reference time change rate required by balancing;

determining a target equalization duration of the single battery to be equalized according to a time change rate of the single battery to be equalized in the battery pack, the reference time change rate and a preset equalization duty ratio, wherein the equalization duty ratio is a ratio of an equalization time period to a unit cycle in the unit cycle, and the unit cycle comprises the equalization time period and a sampling time period;

and controlling the balance of the single battery to be balanced in the balancing time period of the unit cycle according to the target balancing duration.

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

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

the acquisition module is used for acquiring battery information of a battery pack, and the battery information is used for determining the time change rate of each single battery in the battery pack;

the control module is used for acquiring the time change rate of each single battery in the battery pack; acquiring a reference time change rate required by balancing; determining a target equalization duration of a single battery to be equalized according to a time change rate of the single battery to be equalized, the reference time change rate and a preset equalization duty ratio of the single battery to be equalized of the battery pack, wherein the equalization duty ratio is a ratio of an equalization time period to a unit cycle in the unit cycle, and the unit cycle comprises the equalization time period and a sampling time period; controlling the balance of the single batteries to be balanced in the balancing time period of the unit cycle according to the target balancing duration;

the balancing module is used for balancing the single batteries to be balanced.

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 the second aspect of the present disclosure.

According to the technical scheme, the target equalization time length of the single battery to be equalized is determined according to the time change rate and the reference time change rate of the single battery to be equalized in the battery pack, and then the single battery to be equalized is equalized according to the determined target equalization time length. The target equalization duration according to the equalization process is calculated according to the difference value between the time change rate of the single battery to be equalized and the reference time change rate, so that the equalization process is more accurate, and the occurrence of over-equalization is avoided.

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

Through the technical scheme, the acquisition and the balance of the battery information are carried out in a unit period in a time-sharing manner, so that the influence of balance current on the accuracy of the battery information acquisition is avoided when the battery information acquisition and the balance are carried out simultaneously; on the other hand, the proportion of the equalization time period to the adopted time period in the unit time length can be reflected through the equalization duty ratio, so that the target equalization time length calculated under the condition of considering the equalization duty ratio can better equalize the single batteries needing equalization, and meanwhile, a novel method for determining the target equalization time length is provided.

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 cell 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 specific embodiments of the present disclosure is provided in connection with 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: a control module 101, an acquisition module 102 and a balancing module 103. The battery equalization system can be used to equalize the battery pack 104.

In one embodiment, each cell 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 cells may share an equalization module, for example, N cells in a battery pack, the same equalization module may be shared, or one equalization module may be shared for each predetermined number (e.g., 2, 3, or 5, etc.) of cells, and so on. 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 of the two single batteries 111 is switched from the closed state to the open state or from the open state to the closed state every two seconds in 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, and an equalization module 303, which can be used to equalize a battery pack 304. The battery pack 304 includes a plurality of unit cells connected in series. The control module 301 is connected with the acquisition module 302 and the equalization module 303 corresponding to the same single battery through a control channel 305, and the control module 301 is used for controlling the control module 301 to be connected with the corresponding sampling module 302 when determining that the single battery connected with the control module 301 does not need to be equalized; or, the control module 301 is further configured to multiplex the channel 305 in time division according to a unit cycle by the acquisition module 302 and the equalization module 303 when it is determined that the cell connected to the control module 301 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 in 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 for 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 with the acquisition module 302, the control module 301 controls the acquisition module 302 to acquire battery information of the single battery in an acquisition period; 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. 3, 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 time rate of change of each unit cell in the battery pack is acquired;

in step S52, a reference time change rate required for equalization is acquired;

in step S53, determining a target equalization duration of a cell to be equalized according to a time change rate of the cell to be equalized in the battery pack, the reference time change rate, and a preset equalization duty cycle, where the equalization duty cycle is a ratio of an equalization period to a unit cycle in a unit cycle, and the unit cycle includes the equalization period and a sampling period;

in step S54, balancing of the single battery cells to be balanced is controlled in the balancing period of the unit cycle according to the target balancing duration.

In the sampling period of the unit cycle, the control module controls the acquisition module to acquire the battery information of each single battery in the battery pack respectively, and the time change rate of each single battery can be obtained through the battery information. Wherein, the battery information may for example comprise at least one of the following information: voltage, current, and temperature. At this point, the equalization module stops operating.

And in the balancing time period of the unit cycle, the control module controls the balancing module to balance the module to be balanced in the battery pack. At this point, the sampling module stops working.

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

In one embodiment, the step S51 is not limited to the following embodiments:

acquiring a charging time required for the voltage of each unit cell to rise by one unit voltage (for example, 1V) from an initial terminal voltage during charging of the battery pack;

for each single battery in the battery pack, determining the time change rate value of the single battery as the ratio of the required charging time of the single battery to the value of the unit voltage; alternatively, the first and second electrodes may be,

in the discharging process of the battery pack, acquiring the discharging time required by the voltage of each single battery to be reduced by one unit voltage from the initial terminal voltage;

and for each single battery in the battery pack, determining the time change rate value of the single battery as the ratio of the discharge time required by the single battery to the unit voltage value.

In the charging or discharging process of the battery pack, the voltage change condition of the single batteries is recorded, so that the time change rate of the single batteries can be obtained according to the voltage change condition and the method.

Since, in different SOC states, the rate of change of the voltage of the battery with charge and discharge time is different. Therefore, the SOC state difference of each single battery can be identified according to the difference situation of the time change rate of the batteries, the consistency difference of each single battery is further identified, and the single batteries needing to be balanced are further determined.

In step S52, a reference time change rate is determined from the time change rate of each unit cell.

In one embodiment, the time change rate of any single cell in the battery pack may be used as the reference time change rate, for example, the time change rate of the 2 nd single cell in the battery pack may be used as the reference time change rate, or the time change rate of the single cell with the largest time change rate in the battery pack may be used as the reference time change rate, or the time change rate of the single cell with the smallest time change rate in the battery pack may be used as the reference time change rate, or the time change rate of the single cell with the time change rate in the middle of the battery pack (for the case where the battery pack includes an odd number of single cells).

In another embodiment, the reference time change rate may also be calculated according to the time change rate of each single battery in the battery pack, for example: the average value of the time change rates of the respective unit cells in the battery pack, or the average value of the time change rates of the two unit cells in the battery pack with the time change rate arranged at the middle (for the case where the battery pack includes an even number of unit cells).

Referring to table 1 below, table 1 illustrates a manner of determining a single battery to be equalized from a battery pack when parameters of the single battery to be equalized are respectively a voltage value, an SOC, an internal resistance, a self-discharge rate, a voltage change rate, an electric quantity change rate, or a time change rate, and a manner of subsequently equalizing the corresponding single battery to be equalized after determining the single battery to be equalized.

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 (time t 1), detecting and recording the open-circuit voltage value V1 of each single battery of the power battery pack; when the battery pack starts to work again (time t2), detecting and recording the open-circuit voltage value V2 of each single battery of the power 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) based on an Open Circuit Voltage (OCV) -SOC curve (such as the curve shown in fig. 6) of the battery, finding out an SOC value corresponding to V1 and an SOC value corresponding to V2 from the detected V1 and V2;

(2) calculating the SOC variation value delta SOC of the battery according to the two SOC values respectively corresponding to V1 and V2;

(3) calculating the battery capacity discharged by the battery from the discharge according to the delta SOC and the full-capacity C of the battery, wherein the delta Q is delta SOC C;

(4) calculating the value of the self-discharge rate eta of the battery: η ═ Δ Q/(t1-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 unit cell, a voltage variation amount (dv/dq) of the unit 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 in the amount of charge of the unit cells may be an amount of change in the amount of charge when a unit of a specified physical quantity of the unit cells is changed. For example, the present disclosure will be described by taking as an example the amount of electricity (dq/dv) that needs to be charged by increasing the voltage of the unit cell by one unit voltage from the initial voltage, or the amount of electricity (dq/dv) that decreases by decreasing the voltage of the unit cell by one unit voltage from the initial voltage.

TABLE 1

In the embodiment of the present disclosure, the equalization duty ratio is a ratio of an equalization period to a unit period in the unit period, and may be used to represent a ratio of the equalization period to a sampling period in the unit period. The preset equalization duty cycle may be a preset equalization duty cycle, an equalization duty cycle that is not changed during equalization, such as a setting of 50%, and so on.

Optionally, after determining the single battery needing to be balanced, the target balancing time length of the single battery needing to be balanced may 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 time change rate of the single battery needing equalization, the reference time change rate and the preset equalization duty ratio.

Optionally, determining a target equalization duration of the single battery to be equalized according to the time change rate of the single battery to be equalized, the reference time change rate, and a preset equalization duty cycle, includes:

determining the single battery with the minimum difference between the time change rate value and the reference time change rate value in the battery pack as a reference battery;

when the initial end voltage of the single battery to be balanced is different from the initial end voltage of the reference battery, determining the target balancing duration according to the initial end voltage of the single battery to be balanced, the initial end voltage of the reference battery and the balancing duty ratio;

when the initial end voltage of the single battery to be equalized is the same as the initial end voltage of the reference battery, determining the target equalization time length according to the charging time of the single battery to be equalized, the charging time of the reference battery and the equalization duty ratio, or determining the target equalization time length according to the discharging time of the single battery to be equalized, the discharging time of the reference battery and the equalization duty ratio.

Determining the target equalization duration according to the initial end voltage of the single battery to be equalized, the initial end voltage of the reference battery and the equalization duty ratio, wherein the determining of the target equalization duration comprises the following steps:

determining a first SOC value corresponding to the initial terminal voltage value of the reference battery according to the initial terminal voltage value of the reference battery and an open-circuit voltage OCV-remaining capacity SOC curve of the reference battery;

determining a second SOC value corresponding to the initial terminal voltage value of the single battery to be balanced according to the initial terminal voltage value of the single battery to be balanced and the OCV-SOC curve corresponding to the single battery to be balanced;

and determining the target equalization duration according to the first SOC value, the second SOC value and the equalization duty ratio.

Similarly, determining the target equalization duration according to the charging time of the single battery to be equalized, the charging time of the reference battery and the equalization duty ratio, includes:

determining the capacity difference between the single battery to be equalized and the reference battery according to the charging time required by the voltage of the single battery to be equalized to rise by one unit voltage from the initial end voltage, the charging time required by the voltage of the reference battery to rise by one unit voltage from the initial end voltage and the current integral value

And determining the target equalization duration according to the capacity difference, the equalization duty cycle and the equalization current of the battery to be equalized.

Similarly, determining the target equalization duration according to the discharge time of the single battery to be equalized, the discharge time of the reference battery and the equalization duty ratio, includes:

determining the capacity difference between the single battery to be equalized and the reference battery according to the discharge time required by the voltage of the single battery to be equalized to be reduced by one unit voltage from the initial end voltage, the discharge time required by the voltage of the reference battery to be reduced by one unit voltage from the initial end voltage and the current integral value;

In the embodiment of the present disclosure, the initial terminal voltage is a voltage detected when the battery pack starts charging or discharging, or a voltage of the unit battery detected at a certain set detection timing.

1) When the initial end voltage of the single battery to be equalized is different from the initial end voltage of the reference battery, determining a target equalization duration by the following process:

determining a reference OCV value of the reference battery according to the initial terminal 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 an OCV-SOC curve of the reference battery;

determining an OCV value of the single battery to be balanced according to the initial end voltage value of the single battery to be balanced and the internal resistance value of the single battery to be balanced;

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 of the single battery to be balanced;

according to Δ Q ═ Δ SOC × C_nDetermining a difference in electrical quantities, where Δ Q is the difference in electrical quantities, Δ SOC is a difference in SOC between the first and second SOC values, and C_nThe available capacity of the single battery to be balanced is obtained;

and determining the target equalization time length according to the t ═ delta Q/(I multiplied by tau), wherein t is the target equalization time length, I is the equalization current of the single battery to be equalized, and tau is the equalization duty ratio.

2) When the initial terminal voltage of the single battery to be equalized is the same as the initial terminal voltage of the reference battery, determining a target equalization duration by the following process:

and acquiring the electric quantity difference between the single battery to be equalized and the reference battery by an ampere-hour integration method according to the charging time required for the voltage of the single battery to be equalized to rise (or fall) from the initial terminal voltage by one unit voltage, the charging time required for the voltage of the reference battery to rise (or fall) from the initial terminal voltage by one unit voltage and the current integration value.

Specifically, let the rate of change of charge of the reference battery (dt/dv) be dt0/dv0, and the rate of change of charge of the cell to be equalized (dt/dv) be dt1/dv1, where dv0 ═ dv1 is used to characterize one unit voltage; dt0 is used to characterize the charging time period required by the voltage of the reference cell to rise by a unit voltage, or dt0 is used to characterize the discharging time period required by the voltage of the reference cell to fall by a unit voltage; dt1 is used to characterize the charging time period required for the voltage of the cell to be equalized to rise by a unit voltage, or dt1 is used to characterize the discharging time period required for the voltage of the cell to be equalized to fall by a unit voltage. Then the difference between the charging time periods required for the cell to be equalized and the reference cell voltage to rise by the unit voltage may be determined as Δ t ═ Δ (dt/dv) × dv0, or the difference between the discharging time periods required for the cell to be equalized and the reference cell voltage to fall by the unit voltage may be determined as Δ t ═ Δ (dt/dv) × dv 0; then according to the formula delta Q ═ integral ^ I₀Δ t, determining the volume difference, wherein I₀The reference battery is the real-time charging and discharging current in the charging and discharging processes;

and determining the target equalization time length according to the t ═ Δ Q/(I × τ), wherein Δ Q is the capacity difference, t is the target equalization time length, I is the equalization current, and τ is the equalization duty ratio.

In one embodiment of the present disclosure, the OCV-SOC curve is obtained through measurement. For example, for a certain single battery, in the process of changing the SOC value from 0 to 100%, the open circuit voltage OCV of the primary battery is measured at certain SOC intervals, and then the OCV and the SOC corresponding to each point are in one-to-one correspondence to form the SOC-OCV curve of the single battery. Fig. 6 is a schematic diagram of an OCV-SOC curve of a unit cell.

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 cell is equivalent to an ideal voltage source and is connected in series with the resistor R by using a cell 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_LThe 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.

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 and the second SOC value 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.

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

according to Δ Q ═ Δ SOC × C_nDetermining 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_nThe available capacity of the single battery to be balanced;

And the reference time change rates are different, and the balancing process of the single batteries needing to be balanced is different. Hereinafter, the reference time change rates will be described as the minimum value, the maximum value, and the average value among the time change rates of the individual battery cells in the battery pack.

1) In a case where the reference time change rate is the minimum value among the time change rates of the individual cells in the battery pack, the determining a time change rate difference between the time change rate of the at least one cell and a reference time change rate required for the equalization determination includes: determining a time change rate difference value between the time change rate of the following single batteries and a reference time change rate required by the equalization judgment:

the single battery with the largest time change rate in the battery pack; or

And the other single batteries except the single battery with the time change rate of the minimum value in the battery pack.

Correspondingly, after determining that the single battery needing to be balanced is the single battery with the time change rate difference value larger than or equal to the balancing starting threshold value in the at least one single battery, the method further comprises the following steps: when the battery pack is in a charging process, controlling the charging of the single battery with the time change rate difference value larger than or equal to the equalizing starting threshold value in the at least one single battery; and when the battery pack is in the discharging process, controlling the discharging of the single battery of which the time change rate difference is greater than or equal to the equalizing starting threshold value in the at least one single battery.

Specifically, when the reference time change rate is the minimum value among the time change rates of the individual batteries in the battery pack, only the time change rate of the individual battery with the largest time change rate in the battery pack may be different from the reference time change rate, and it may be determined whether the individual battery with the largest time change rate 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 time change rate is the minimum value among the time change rates of the individual batteries in the battery pack, the time change rates of the individual batteries other than the individual battery with the minimum time change rate in the battery pack may be differentiated from the reference time change rate, so as to determine whether the individual batteries other than the individual battery with the minimum time change rate 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 except the cell with the smallest time change rate in the battery pack are the cells that need to be balanced at one time.

When the reference time change rate is the minimum value of the time change rates of the single batteries in the battery pack, the process of balancing the single batteries needing balancing is as follows:

considering the large time change rate, on the one hand, this may be caused by the small internal resistance of the battery. Another aspect may be due to the presence of a capacity difference, i.e., an initial difference in SOC. The battery with small internal resistance is not seriously aged, and the voltage of the battery rises slowly in the charging process, so that the battery pack discharges the single batteries needing to be balanced when in the charging process; considering that the battery with small internal resistance is not seriously aged, the voltage of the battery is slowly reduced in the discharging process, and therefore, when the battery pack is in the discharging process, the single batteries needing to be balanced are charged.

2) In a case where the reference time change rate is a maximum value among time change rates of the respective unit cells in the battery pack, the determining a time change rate difference between the time change rate of the at least one unit cell and a reference time change rate required for the equalization determination includes: determining a time change rate difference value between the time change rate of the following single batteries and a reference time change rate required by the equalization judgment:

the single battery with the minimum time change rate in the battery pack; or

And the other single batteries except the single battery with the time change rate of the maximum value in the battery pack.

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

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

In the case that the reference time change rate is the maximum value among the time change rates of the individual cells in the battery pack, the process of equalizing the individual cells requiring equalization is as follows:

3) In a case where the reference time change rate is an average value of time change rates of the individual cells in the battery pack, the determining a time change rate difference between the time change rate of the at least one cell and a reference time change rate required for the equalization determination includes: and determining a time change rate difference value between the time change rate of each single battery in the battery pack and the reference time change rate.

Correspondingly, after determining that the single battery needing to be balanced is the single battery with the time change rate difference value larger than or equal to the balancing starting threshold value in the at least one single battery, the method further comprises the following steps:

when the battery pack is in a charging process, controlling the single batteries with the time change rate smaller than the average value in the single batteries needing to be balanced to discharge, and controlling the single batteries with the time change rate larger than the average value in the single batteries needing to be balanced to charge;

and when the battery pack is in a discharging process, controlling the single batteries with the time change rates smaller than the average value in the single batteries needing to be balanced to be charged, and controlling the single batteries with the time change rates larger than the average value in the single batteries needing to be balanced to be discharged.

Specifically, when the reference time change rate is an average value of the time change rates of the individual batteries in the battery pack, the time change rate of each individual battery in the battery pack may be different from the reference time change rate, 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 time change rate is the average value of the time change rates of the single batteries in the battery pack, the process of balancing the single batteries needing balancing is as follows:

considering the large time change rate, on the one hand, this may be caused by the small internal resistance of the battery. Another aspect may be due to the presence of a capacity difference, i.e., an initial difference in SOC. The battery with small internal resistance is not seriously aged, the voltage of the battery rises slowly in the charging process, and the voltage of the battery drops slowly in the discharging process, so that when the battery pack is in the charging process, the battery pack discharges the single battery with the time change rate smaller than the average value of the time change rate in the single battery needing to be balanced, and charges the single battery with the time change rate larger than the average value of the time change rate in the single battery needing to be balanced; similarly, when the battery pack is in the discharging process, the single batteries with the time change rate smaller than the average value of the time change rate in the single batteries needing to be balanced are charged, and the single batteries with the time change rate larger than the average value of the time change rate in the single batteries needing to be balanced are discharged.

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 time change rate 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 equalizing module according to an embodiment of the disclosure. And controlling the single batteries to be balanced, wherein the balancing judgment needs to be combined. According to the step of equalization judgment, 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) is determined, and the corresponding equalization module is conducted.

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 achieve 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 battery 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 with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details of 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 cell balancing, the method comprising:

acquiring the time change rate of each single battery in the battery pack;

acquiring a reference time change rate required by balancing;

judging whether the initial terminal voltage of the single battery to be equalized in the battery pack is the same as the initial terminal voltage of the reference battery;

when the initial end voltage of the single battery to be equalized is the same as the initial end voltage of the reference battery, determining a target equalization time length of the single battery to be equalized according to the charging time of the single battery to be equalized, the charging time of the reference battery and a preset equalization duty ratio, or determining the target equalization time length according to the discharging time of the single battery to be equalized, the discharging time of the reference battery and the equalization duty ratio, wherein the equalization duty ratio is the ratio of an equalization time period to a unit cycle in the unit cycle, and the unit cycle comprises the equalization time period and a sampling time period;

2. The method as claimed in claim 1, further comprising, after determining whether the initial terminal voltage of the single battery to be equalized is the same as the initial terminal voltage of the reference battery, the steps of:

and when the initial end voltage of the single battery to be balanced is different from the initial end voltage of the reference battery, determining the target balancing duration according to the initial end voltage of the single battery to be balanced, the initial end voltage of the reference battery and the balancing duty ratio.

3. The method as claimed in claim 2, wherein the determining the target equalization duration according to the initial terminal voltage of the single battery to be equalized, the initial terminal voltage of the reference battery and the equalization duty ratio comprises:

4. The method as claimed in claim 3, wherein said determining a first SOC value corresponding to an initial terminal voltage value of said reference battery from said initial terminal voltage value of said reference battery and an OCV-SOC curve of said reference battery comprises:

determining a second SOC value corresponding to the initial terminal voltage value of the single battery to be equalized according to the initial terminal voltage value of the single battery to be equalized and the OCV-SOC curve corresponding to the single battery to be equalized, wherein the determining step comprises the following steps:

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 of the single battery to be balanced.

5. The method of claim 4, wherein determining the target equalization duration based on the first SOC value, the second SOC value, and the equalization duty cycle comprises:

6. The method according to claim 1, wherein the determining the target equalization duration according to the charging time of the single battery to be equalized, the charging time of the reference battery and the equalization duty ratio, or determining the target equalization duration according to the discharging time of the single battery to be equalized, the discharging time of the reference battery and the equalization duty ratio comprises:

determining the capacity difference of the battery to be equalized and the reference battery according to the charging time required by the voltage of the battery cell to be equalized to rise by one unit voltage from the initial end voltage, the charging time required by the voltage of the reference battery to rise by one unit voltage from the initial end voltage and the current integral value, or determining the capacity difference of the battery to be equalized and the reference battery according to the discharging time required by the voltage of the battery cell to be equalized to fall by one unit voltage from the initial end voltage, the discharging time required by the voltage of the reference battery to fall by one unit voltage from the initial end voltage and the current integral value;

7. The method according to claim 6, wherein the determining the target equalization duration according to the capacity difference, the equalization duty cycle and the equalization current of the battery to be equalized comprises:

8. The method according to claim 1, wherein the obtaining the time change rate of the single batteries to be equalized in the battery pack comprises:

in the charging process of the battery pack, acquiring the charging time required by the voltage of the single battery to be equalized to rise by one unit voltage from the initial terminal voltage;

determining the time change rate value of the single battery to be equalized to be the ratio of the required charging time of the single battery to the unit voltage value; alternatively, the first and second electrodes may be,

in the discharging process of the battery pack, acquiring the discharging time required by the voltage of the single battery to be balanced to be reduced by one unit voltage from the initial terminal voltage;

and determining the time change rate value of the single battery to be equalized to be the ratio of the discharge time required by the single battery to the unit voltage value.

9. The method of claim 1, wherein obtaining the reference time change rate required for equalization comprises:

determining a minimum time change rate value of the time change rate values of the single batteries in the battery pack as the reference time change rate; or the like, or, alternatively,

determining the maximum time change rate value of the time change rate values of the single batteries in the battery pack as the reference time change rate; or the like, or, alternatively,

and determining the average value of the time change rate values of the single batteries in the battery pack as the reference time change rate.

10. The method of claim 1, further comprising:

and determining the single batteries to be balanced from the battery pack according to battery parameter information of each single battery in the battery pack, wherein the battery parameter information comprises at least one of a voltage value, an internal resistance value, a self-discharge rate value, an SOC value, an electric quantity change rate and a voltage change rate.

11. A battery equalization system, comprising: a balancing module, an acquisition module and a control module,

the control module is used for acquiring the time change rate of each single battery in the battery pack; acquiring a reference time change rate required by balancing; determining the single battery with the minimum difference between the time change rate value and the reference time change rate value in the battery pack as a reference battery; judging whether the initial terminal voltage of the single battery to be equalized in the battery pack is the same as the initial terminal voltage of the reference battery; when the initial end voltage of the single battery to be equalized is the same as the initial end voltage of the reference battery, determining a target equalization time length of the single battery to be equalized according to the charging time of the single battery to be equalized, the charging time of the reference battery and a preset equalization duty ratio, or determining the target equalization time length according to the discharging time of the single battery to be equalized, the discharging time of the reference battery and the equalization duty ratio, wherein the equalization duty ratio is the ratio of an equalization time period to a unit cycle in the unit cycle, and the unit cycle comprises the equalization time period and a sampling time period; controlling the balance of the single batteries to be balanced in the balancing time period of the unit cycle according to the target balancing duration;

the balancing module is used for balancing the single batteries to be balanced.

12. The battery equalization system of claim 11, wherein the control module is further configured to:

after judging whether the initial end voltage of the single battery to be equalized is the same as the initial end voltage of the reference battery or not, when the initial end voltage of the single battery to be equalized is different from the initial end voltage of the reference battery, determining the target equalization duration according to the initial end voltage of the single battery to be equalized, the initial end voltage of the reference battery and the equalization duty ratio.

13. The battery equalization system of claim 12, wherein the control module is configured to:

14. The battery equalization system of claim 13, wherein the control module is configured to:

15. The battery equalization system of claim 14, wherein the control module is configured to:

16. The battery equalization system of claim 11, wherein the control module is configured to:

17. The battery equalization system of claim 16, wherein the control module is configured to:

18. The battery equalization system of claim 11, wherein the control module is configured to:

19. The battery equalization system of claim 11, wherein the control module is configured to:

20. The battery equalization system of claim 11, wherein the control module is further configured to:

21. The battery equalization system of claim 11, 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; alternatively, the first and second electrodes may be,

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.

22. The battery equalization system of claim 21, 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.

23. The battery equalization system of claim 11, wherein the control module is connected to the acquisition module and the equalization module corresponding to the same cell through two channels.

24. The battery equalization system of claim 23, 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.

25. A computer-readable storage medium, on which computer program instructions are stored, which program instructions, when executed by a processor, implement the method of any one of claims 1-10.

26. An electronic device, comprising:

the computer-readable storage medium recited in claim 25; and

27. A vehicle, characterized in that the vehicle comprises: a battery pack and a battery equalization system as claimed in any of claims 11-24.