JP2021090275A - Calculation device and full charge capacity calculation method - Google Patents

Abstract

To improve the accuracy of calculating the full charge capacity.SOLUTION: A calculation device according to an embodiment comprises an acquisition unit, an equalization control unit, and a calculation unit. The acquisition unit acquires the first open-circuit voltage of the battery before the start of discharge of the above battery and the second open-circuit voltage of the battery after the stop of discharge of the above battery, respectively, when calculating the full charge capacity of a battery consisting of a secondary battery. The equalization control unit executes equalization of the cells of the battery before the acquisition unit acquires the first open-circuit voltage. The calculation unit calculates the above full charge capacity based on the first open-circuit voltage, the second open-circuit voltage, and the current accumulation during the discharge of the battery.SELECTED DRAWING: Figure 2

Description

The disclosed embodiments relate to a calculation device and a full charge capacity calculation method.

Conventionally, a method of calculating the full charge capacity of a lithium ion secondary battery (LiB: Lithium-Ion rechargeable battery) mounted on an HEV (Hybrid Electric Vehicle), an EV (Electric Vehicle), or the like has been known (for example, a patent). Reference 1).

For example, the ΔSOC (State Of Charge) method is a method of calculating the full charge capacity based on the SOC difference before and after charging / discharging and the current integrated amount between them. The SOC is estimated based on the OCV-SOC curve showing the relationship between the open circuit voltage (OCV) and the SOC.

Japanese Unexamined Patent Publication No. 2014-174050

However, the above-mentioned prior art has room for further improvement in improving the accuracy of calculating the full charge capacity.

One aspect of the embodiment is made in view of the above, and an object of the present invention is to provide a calculation device and a full charge capacity calculation method capable of improving the calculation accuracy of the full charge capacity.

The calculation device according to one aspect of the embodiment includes an acquisition unit, an equalization control unit, and a calculation unit. When calculating the full charge capacity of a battery composed of a secondary battery, the acquisition unit obtains a first open voltage of the battery before the start of discharge of the battery and a second open voltage of the battery after the discharge of the battery is stopped. And get each. The equalization control unit executes equalization of the cells of the battery before the acquisition of the first open circuit voltage by the acquisition unit. The calculation unit calculates the full charge capacity based on the first open circuit voltage, the second open circuit voltage, and the integrated current amount during discharge of the battery.

According to one aspect of the embodiment, the accuracy of calculating the full charge capacity can be improved.

FIG. 1A is a schematic explanatory view (No. 1) of the full charge capacity calculation method according to the comparative example. FIG. 1B is a schematic explanatory view (No. 2) of the full charge capacity calculation method according to the comparative example. FIG. 1C is a schematic explanatory view (No. 3) of the full charge capacity calculation method according to the comparative example. FIG. 1D is a schematic explanatory view (No. 1) of the full charge capacity calculation method according to the embodiment. FIG. 1E is a schematic explanatory view (No. 2) of the full charge capacity calculation method according to the embodiment. FIG. 2 is a block diagram of the battery control system according to the embodiment. FIG. 3 is a flowchart showing a processing procedure executed by the calculation device according to the embodiment.

Hereinafter, embodiments of the calculation device and the full charge capacity calculation method disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

Further, in the following, a case where the calculation device to which the full charge capacity calculation method according to the embodiment is applied is a battery ECU (Electronic Control Unit) 10 for controlling LiB2 mounted on the vehicle will be described as an example.

First, the outline of the full charge capacity calculation method according to the embodiment will be described with reference to FIGS. 1A to 1E. 1A to 1C are schematic explanatory views (No. 1) to (No. 3) of the full charge capacity calculation method according to the comparative example. Further, FIGS. 1D and 1E are schematic explanatory views (No. 1) and (No. 2) of the full charge capacity calculation method according to the embodiment.

Prior to the method for calculating the full charge capacity according to the embodiment, a comparative example will be described first. As shown in FIG. 1A, when the full charge capacity is calculated by the ΔSOC method, for example, OCV _{Hi before discharge and OCV Lo} after discharge and after polarization elimination are acquired, respectively.

Then, based on the OCV-SOC curve shown in FIG. 1B, _{the SOC corresponding to each of OCV Hi} and OCV _Lo is estimated, and the full charge capacity is calculated using the difference and the integrated current amount during discharging.

However, such a method has two problems as shown in FIG. 1C. The first is that _{there is a variation in the cell voltage when acquiring OCV Hi} before discharging, and if any of the cell voltages is out of the predetermined range, the cell voltage is unreliable and the full charge capacity can be calculated. Can not.

Second, if the cell voltage varies during discharge, one of the cells will exceed the target voltage when _{the OCV Lo is acquired after discharge.} In such a case, although the full charge capacity can be calculated, the accuracy deteriorates.

Therefore, in the full charge capacity calculation method according to the embodiment, before the acquisition of OCV _Hi, and performs cell equalization, it was decided to eliminate the dispersion of the cell voltage before the acquisition of OCV _Hi. Further, it was decided to carry out cell equalization _{after discharge and before acquisition of OCV Lo} after elimination of polarization to eliminate variations in cell voltage before acquisition of _{OCV Lo.}

Specifically, as shown in FIG. 1D, in the full charge capacity calculation method according to the embodiment, OCV _Hi is acquired after cell equalization is performed. In this way, _{by performing cell equalization in advance before acquiring OCV Hi} , the cell voltage can be kept within a predetermined range and the reliability of the cell voltage can be ensured.

Further, as shown in FIG. 1E, in the full charge capacity calculation method according to the embodiment, OCV _Lo is acquired after performing cell equalization after discharging to the required discharge voltage and after eliminating polarization. At this time, cell equalization is performed only for cells exceeding the target voltage. In this way, _{by performing cell equalization in advance before acquiring OCV Lo} , all cell voltages can be kept below the target voltage, and the accuracy of the calculated full charge capacity can be prevented from deteriorating. Can be done.

The processes shown in FIGS. 1D and 1E may be performed by both or only one of them when calculating the full charge capacity.

As described above, in the full charge capacity calculation method according to the embodiment, after performing cell equalization, OCV _Hi is acquired, and after discharging to the required discharge voltage and after eliminating polarization, cell equalization is performed. , _{Obtaining OCV Lo} , or at least one of them.

Then, in the full charge capacity calculation method according to the embodiment, the full charge capacity is calculated by the ΔSOC method based on the _{acquired OCV Hi} and OCV _Lo.

Thereby, according to the full charge capacity calculation method according to the embodiment, the calculation accuracy of the full charge capacity can be improved.

Hereinafter, a configuration example of the battery control system 1 to which the full charge capacity calculation method according to the above-described embodiment is applied will be described in more detail.

FIG. 2 is a block diagram of the battery control system 1 according to the embodiment. Note that, in FIG. 2, only the components necessary for explaining the features of the present embodiment are represented by functional blocks, and the description of general components is omitted.

In other words, each component shown in FIG. 2 is a functional concept and does not necessarily have to be physically configured as shown in the figure. For example, the specific form of distribution / integration of each functional block is not limited to the one shown in the figure, and all or part of the functional blocks are functionally or physically distributed in arbitrary units according to various loads and usage conditions. -It is possible to integrate and configure.

As shown in FIG. 2, the battery control system 1 includes a LiB2, a cell balance IC (Integrated Circuit) 3, a charge / discharge IC 4, a voltage sensor 5, a current sensor 6, a battery ECU 10, and a host ECU 20. .. LiB2 is a lithium ion secondary battery and includes a plurality of cells C connected in series inside.

The cell balance IC 3 executes cell equalization to equalize the energy capacity of the cell C in the LiB2 based on the instruction from the battery ECU 10.

The charge / discharge IC4 charges / discharges LiB2 based on an instruction from the battery ECU 10.

The voltage sensor 5 is a sensor that measures the battery voltage of LiB2. For example, the voltage sensor 5 can measure the OCV of LiB2. The current sensor 6 is a sensor that measures the charge / discharge current of LiB2.

The battery ECU 10 includes a storage unit 11 and a control unit 12. The storage unit 11 is realized by, for example, a semiconductor memory element such as a RAM (Random Access Memory) or a flash memory (Flash Memory), or a storage device such as a hard disk or an optical disk. In the example of FIG. 2, the OCV-SOC curve 11a Remember. The OCV-SOC curve 11a corresponds to the OCV-SOC curve described with reference to FIG. 1B.

Further, as shown in FIG. 2, the control unit 12 is a controller, and for example, various programs stored in the storage unit 11 by a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or the like. Is realized by executing RAM as a work area. Further, the control unit 12 can be realized by, for example, an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

The control unit 12 includes an equalization control unit 12a, a charge / discharge control unit 12b, an acquisition unit 12c, and a calculation unit 12d, and realizes or executes an information processing function or operation described below.

The equalization control unit 12a causes the cell balance IC 3 to execute the cell equalization of LiB2 before acquiring _{the OCV Hi in the full charge capacity calculation process.} Further, the equalization control unit 12a causes the cell balance IC3 to perform cell equalization of LiB2 in the _{process of calculating the full charge capacity before acquiring OCV Lo} after discharging to the required discharge voltage and after resolving the polarization.

The equalization control unit 12a executes cell equalization only for the cell C exceeding the target voltage in the cell equalization before the acquisition of the _{OCV Lo.}

The charge / discharge control unit 12b causes the charge / discharge IC4 to discharge LiB2 so as to start discharging after acquiring _{OCV Hi and discharge until the required discharge voltage is reached in the full charge capacity calculation process.}

_{The acquisition unit 12c acquires OCV Hi} via the voltage sensor 5 after the cell equalization by the equalization control unit 12a and before the start of discharge by the charge / discharge control unit 12b. _{Further, the acquisition unit 12c acquires the OCV Lo} via the voltage sensor 5 after the charge / discharge control unit 12b stops the discharge and the polarization is eliminated, and after the cell equalization by the equalization control unit 12a.

Further, the acquisition unit 12c acquires the integrated current amount during discharge by the charge / discharge control unit 12b via the current sensor 6.

The calculation unit 12d calculates the _{full charge capacity by the ΔSOC method based on the OCV Hi} , OCV _Lo , current integrated amount, and OCV-SOC curve 11a acquired by the acquisition unit 12c. Further, the calculation unit 12d outputs the calculated full charge capacity to, for example, the upper ECU 20.

The upper ECU 20 is a higher ECU of the battery ECU 10, and intermittently activates the battery ECU 10 while the IG (ignition) is off to execute the full charge capacity calculation process.

Next, the processing procedure executed by the battery ECU 10 according to the embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing a processing procedure executed by the battery ECU 10 according to the embodiment.

As shown in FIG. 3, the battery ECU 10 is intermittently started by the upper ECU 20 while the IG is off (step S101), and the full charge capacity calculation process is started. First, the equalization control unit 12a causes the cell balance IC3 to execute cell equalization (step S102).

Then, after the end of step S102, it is determined whether or not no current is flowing and the voltage values of all cells are equal to or higher than a certain level (step S103). Here, if no current is flowing and the voltage values of all cells are equal to or higher than a certain value (step S103, Yes), the acquisition unit 12c acquires OCV _Hi (step S104).

Then, the charge / discharge control unit 12b causes the charge / discharge IC4 to start discharging (step S105). The charge / discharge control unit 12b determines whether or not the voltage has reached the discharge voltage or lower during discharging (step S106), and if the charge / discharge voltage has not reached the discharge voltage or lower (steps S106, No), repeats step S106.

On the other hand, if the voltage reaches the discharge voltage or less (step S106, Yes), the charge / discharge IC4 is stopped from discharging (step S107). Then, after the polarization is eliminated, the equalization control unit 12a causes the cell balance IC3 to execute cell equalization (step S108).

Then, after cell equalization in step S108, the acquisition unit 12c acquires OCV _Lo (step S109). Then, the calculation unit 12d calculates the _{full charge capacity by the ΔSOC method based on the OCV Hi} , OCV _Lo and the current integrated amount acquired by the acquisition unit 12c (step S110), and ends the process.

If the determination condition of step S103 is not satisfied (steps S103, No), the process ends.

As described above, the battery ECU 10 (corresponding to an example of the “calculation device”) according to the embodiment includes an acquisition unit 12c, an equalization control unit 12a, and a calculation unit 12d. When calculating the full charge capacity of LiB2 (corresponding to an example of a "battery composed of a secondary battery"), the acquisition unit 12c is used as an example of the OCV _{Hi of} LiB2 (corresponding to an example of the "first open circuit voltage") that is applied before the start of discharging LiB2. _{(Equivalent) and OCV Lo of} LiB2 (corresponding to an example of “second open circuit voltage”) applied after the discharge of LiB2 is stopped are obtained, respectively. The equalization control unit 12a executes the equalization of the cell C of LiB2 before the acquisition unit 12c acquires the OCV _Hi. The calculation unit 12d calculates the full charge capacity based on the current integrated amount during discharge of _{OCV Hi} , OCV _{Lo, and LiB2.}

Therefore, according to the battery ECU 10 according to the embodiment, it is possible to improve the calculation accuracy of the full charge capacity by eliminating the variation in the voltage of the cell C before acquiring _{the OCV Hi.} Further, by improving the calculation accuracy of the full charge capacity, it is possible to improve the usage efficiency of the battery performance.

Further, the battery ECU 10 according to the embodiment includes an acquisition unit 12c, an equalization control unit 12a, and a calculation unit 12d. When calculating the full charge capacity of LiB2, the acquisition unit 12c acquires the OCV _{Hi of LiB2 before the start of discharge of LiB2 and the OCV Lo of} LiB2 after the discharge of LiB2 is stopped. The equalization control unit 12a executes equalization of the cell C of LiB2 before the acquisition unit 12c acquires the OCV _Lo. The calculation unit 12d calculates the full charge capacity based on the current integrated amount during discharge of _{OCV Hi} , OCV _{Lo, and LiB2.}

Therefore, according to the battery ECU 10 according to the embodiment, it is possible to improve the calculation accuracy of the full charge capacity by eliminating the variation in the voltage of the cell C before acquiring _{the OCV Lo.} Further, by improving the calculation accuracy of the full charge capacity, it is possible to improve the usage efficiency of the battery performance.

Further, the equalization control unit 12a executes equalization only for the cell C exceeding the predetermined target voltage before the acquisition _{of the OCV Lo and after the polarization is eliminated.}

Therefore, according to the battery ECU 10 according to the embodiment, the calculation accuracy of the full charge capacity is improved by eliminating the voltage variation only in the cell C exceeding the target voltage before the acquisition of _{the OCV Lo and after the polarization is eliminated.} be able to.

In the above-described embodiment, as shown in FIG. 2, an example in which the battery ECU 10 is configured separately from the LiB2 is given, but the present invention is not limited to this, and for example, the battery ECU10 and the LiB2 are used as one battery pack. May be integrally configured.

Further, the battery ECU 10 may be configured integrally with the host ECU 20 and may be configured as a part of the function of the control device that controls the entire vehicle in an integrated manner, for example.

Further, in the above-described embodiment, the case where the battery ECU 10 is a calculation device for calculating the full charge capacity of the LiB2 mounted on the vehicle is given as an example, but the present invention is not limited to this, and the mounting destination of the LiB2 is not questioned. Absent. Therefore, it can be applied to the case where LiB2 is mounted in addition to the vehicle.

Further effects and variations can be easily derived by those skilled in the art. For this reason, the broader aspects of the invention are not limited to the particular details and representative embodiments expressed and described as described above. Therefore, various modifications can be made without departing from the spirit or scope of the general concept of the invention as defined by the appended claims and their equivalents.

1 Battery control system 2 LiB
3 Cell balance IC
4 Charge / discharge IC
5 Voltage sensor 6 Current sensor 10 Battery ECU
11 Storage unit 11a OCV-SOC curve 12 Control unit 12a Equalization control unit 12b Charge / discharge control unit 12c Acquisition unit 12d Calculation unit 20 Upper ECU
C cell

Claims (5)

When calculating the full charge capacity of a battery composed of a secondary battery, the first open voltage of the battery is acquired before the start of discharging the battery, and the second open voltage of the battery is obtained after the discharge of the battery is stopped. Acquisition department and
An equalization control unit that executes equalization of the cells of the battery before the acquisition of the first open circuit voltage by the acquisition unit.
A calculation device including a calculation unit that calculates the full charge capacity based on the first open circuit voltage, the second open circuit voltage, and the integrated current amount during discharge of the battery. When calculating the full charge capacity of a battery composed of a secondary battery, the first open voltage of the battery is acquired before the start of discharging the battery, and the second open voltage of the battery is obtained after the discharge of the battery is stopped. Acquisition department and
An equalization control unit that executes equalization of the cells of the battery before the acquisition of the second open circuit voltage by the acquisition unit.
A calculation device including a calculation unit that calculates the full charge capacity based on the first open circuit voltage, the second open circuit voltage, and the integrated current amount during discharge of the battery. The equalization control unit
The calculation device according to claim 2, wherein equalization is executed only for the cells exceeding a predetermined target voltage before the acquisition of the second open circuit voltage and after the polarization is eliminated. When calculating the full charge capacity of a battery composed of a secondary battery, the first open voltage of the battery is acquired before the start of discharging the battery, and the second open voltage of the battery is obtained after the discharge of the battery is stopped. Acquisition process and
Before the acquisition of the first open circuit voltage in the acquisition step, the equalization control step of executing the equalization of the cells of the battery, the first open circuit voltage, the second open circuit voltage, and the discharge of the battery. A method for calculating a full charge capacity, which comprises a calculation step of calculating the full charge capacity based on the integrated current amount in the medium. When calculating the full charge capacity of a battery composed of a secondary battery, the first open voltage of the battery is acquired before the start of discharging the battery, and the second open voltage of the battery is obtained after the discharge of the battery is stopped. Acquisition process and
Before the acquisition of the second open circuit voltage in the acquisition step, the equalization control step of executing the equalization of the cells of the battery and the equalization control step.
Full charge capacity calculation including a calculation step of calculating the full charge capacity based on the first open circuit voltage, the second open circuit voltage, and the integrated current amount during discharge of the battery. Method.

Images