JP2014092431A - Charging system and method for calculating voltage drop quantity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it is not possible to grasp the voltage drop quantity of a power storage device unless the polarization of the power storage device is solved in the case of charging the power storage device.SOLUTION: A charging system (20) includes: a voltage sensor (22) for detecting the voltage of a power storage device to be charged/discharged; and a controller (24) for allowing the power storage device to be charged during a predetermined time with constant currents. The controller subtracts the variation of the voltage of the power storage device after the occurrence of a voltage rise accompanied by polarization from the variation of the voltage of the power storage device during charging to calculate voltage drop quantity after the end of the charging.

Description

  The present invention relates to a technique for calculating a voltage drop amount associated with elimination of polarization without leaving a power storage device.

  When the secondary battery is charged / discharged, polarization occurs, so the CCV (Closed Circuit Voltage) of the secondary battery is equal to the amount of voltage change associated with the polarization by the OCV (Open Circuit Voltage) of the secondary battery. Deviation from the open circuit voltage. Here, if the secondary battery is left without being charged / discharged, the polarization can be eliminated. Therefore, the OCV of the secondary battery can be obtained after the polarization is eliminated.

JP 2005-043339 A

  If the secondary battery must be left until the polarization of the secondary battery is eliminated, the time required to obtain the OCV of the secondary battery will increase. In other words, the time until the voltage drop amount of the secondary battery is grasped is extended. For example, when inspecting a secondary battery based on the OCV of the secondary battery after charging the secondary battery, the time for inspecting the secondary battery is increased as the time for acquiring the OCV of the secondary battery is extended. Will extend.

  A charging system according to a first invention of the present application includes a voltage sensor that detects a voltage of a power storage device that performs charging and discharging, and a controller that charges the power storage device with a constant current for a predetermined time. Here, the controller subtracts the amount of change in the voltage of the power storage device after the voltage increase caused by the polarization from the amount of change in the voltage of the power storage device between the start and end of charging, The amount of voltage drop after charging is calculated.

  When the charging of the power storage device is started, a voltage increase due to the polarization of the power storage device occurs, and when the charging of the power storage device is finished, a voltage drop due to the cancellation of the polarization occurs. Here, in the first invention of this application, since the power storage device is charged with a constant current, it can be considered that the voltage increase amount and the voltage decrease amount are equal to each other.

  For this reason, a value obtained by subtracting the voltage change amount after the voltage increase caused by the polarization from the voltage change amount from the start to the end of charging is the voltage drop amount. Here, the amount of voltage change after the voltage increase due to polarization occurs is the amount of change in the voltage of the power storage device from immediately after the voltage increase due to polarization to the end of charging.

  According to the first invention of this application, the voltage drop amount after the charging is stopped can be calculated only by monitoring the voltage change while charging the power storage device. Accordingly, the power storage device does not need to be left without being charged / discharged until the polarization is eliminated, in other words, until the voltage drop does not occur. That is, the voltage drop amount can be quickly grasped without leaving the power storage device.

  Specifically, the voltage drop amount can be calculated based on the following formula (I).

  In the above formula (I), ΔVd represents a voltage drop amount. Vs indicates the voltage of the power storage device at the start timing of charging. Since the voltage Vs can be detected before the charging of the power storage device is started, the voltage Vs as an open circuit voltage can be acquired. Ve ′ indicates the voltage (closed circuit voltage) of the power storage device at the end timing of charging.

  In the above formula (I), Vm ′ represents the voltage (closed circuit voltage) of the power storage device at the timing (referred to as the central timing) located at the center between the start timing and the end timing. The center timing is a timing during charging, and the interval (time) between the start timing and the center timing is equal to the interval (time) between the center timing and the end timing.

  In the first invention of this application, since the power storage device is charged for a predetermined time, the start timing and the end timing can be determined in advance. If the start timing and end timing are determined, the central timing can be determined. According to the above formula (I), the voltage drop amount ΔVd can be calculated only by detecting the voltages Vs, Ve ′, and Vm ′ using the voltage sensor. In other words, the amount of voltage drop ΔVd can be specified as charging of the power storage device is terminated.

  If the amount of voltage drop is subtracted from the closed circuit voltage of the power storage device when charging is completed, the open circuit voltage of the power storage device when charging is completed can be calculated. If the power storage device is left until the polarization of the power storage device is eliminated, the open circuit voltage of the power storage device can be detected. However, according to the first invention of this application, the power storage device can be provided without leaving the power storage device. With the end of charging, the open circuit voltage of the power storage device can be specified.

  Since the open circuit voltage and the state of charge (SOC) have a predetermined correspondence, the state of charge corresponding to the open circuit voltage can be specified by obtaining this correspondence in advance. As described above, since the open circuit voltage of the power storage device can be calculated without leaving the power storage device unattended, the state of charge of the power storage device can be quickly identified accordingly.

  The amount of voltage drop depends on the temperature of the power storage device. Here, when charging the power storage device, the temperature of the power storage device may increase with the charging. In this case, the voltage drop amount can be corrected in consideration of the temperature rise of the power storage device. The temperature of the power storage device can be detected using a temperature sensor.

  Specifically, the correspondence relationship between the temperature of the power storage device and the amount of voltage drop is obtained in advance, the amount of change in the voltage drop when the temperature of the power storage device changes with charging, and the amount of change is corrected. Can be used as a value. That is, the difference between the voltage drop amount corresponding to the temperature of the power storage device before the change and the voltage drop amount corresponding to the temperature of the power storage device after the change can be used as a correction value for the voltage drop amount. When correcting the voltage drop amount, a correction value may be added to the voltage drop amount calculated as described above.

  By correcting the voltage drop amount in consideration of the temperature change of the power storage device, the accuracy of the voltage drop amount can be improved. If the accuracy of the voltage drop amount can be improved, the open circuit voltage and the charged state of the power storage device can be calculated with high accuracy.

  A second invention of the present application is a method for calculating a voltage drop amount of a power storage device. The method includes a step of charging the power storage device at a constant current for a predetermined time, a step of detecting a voltage of the power storage device, and a step of calculating a voltage drop amount after the charging is finished. Here, the amount of voltage drop is obtained by subtracting the amount of change in the voltage of the power storage device after the voltage increase due to polarization occurs from the amount of change in the voltage of the power storage device between the start and end of charging. Is calculated by Also in the second invention of the present application, the same effect as that of the first invention of the present application can be obtained.

It is a figure which shows the structure of a charge tester. It is a flowchart which shows the process of a charge tester. It is a figure which shows the relationship between charging time and the voltage value of an assembled battery. It is a figure explaining the timing which detects the voltage value of an assembled battery during charge time. It is a figure which shows the relationship between the amount of voltage drops, and the temperature of an assembled battery.

  Examples of the present invention will be described below.

  FIG. 1 is a diagram showing a configuration of a charge inspection machine (corresponding to a charging system) for inspecting a assembled battery (corresponding to a power storage device) after manufacture. The charge inspection machine 20 of the present embodiment charges the assembled battery 10 after manufacture, and determines whether or not the SOC (State of Charge) of the assembled battery 10 is included in an allowable range. Here, when the SOC of the assembled battery 10 is within the allowable range, the charging process of the assembled battery 10 (part of the inspection process) is completed.

  The SOC is the ratio of the current charge capacity to the full charge capacity. Since the SOC and the OCV have a predetermined correspondence relationship, the SOC of the assembled battery 10 can be specified by detecting the OCV of the assembled battery 10 by using this correspondence relationship. Here, the correspondence relationship between the SOC and the OCV can be obtained in advance by an experiment or the like.

  The assembled battery 10 is configured by electrically connecting a plurality of unit cells 11 in series. As the cell 11, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. In addition, an electric double layer capacitor can be used instead of the secondary battery.

  The assembled battery 10 can be mounted on a vehicle, for example. Here, if the motor / generator converts the electrical energy output from the assembled battery 10 into kinetic energy, the vehicle can be driven using this kinetic energy. Further, if the motor / generator converts kinetic energy generated during braking of the vehicle into electric energy, the electric energy can be stored in the assembled battery 10.

  In this embodiment, all the unit cells 11 constituting the assembled battery 10 are electrically connected in series, but the present invention is not limited to this. Specifically, the assembled battery 10 may include a plurality of unit cells 11 electrically connected in parallel.

  The positive electrode terminal of the assembled battery 10 is connected to the charge inspection machine 20 via the positive electrode line PL. Specifically, the charging tester 20 has a power supply device 21, and the positive terminal of the assembled battery 10 is connected to the power supply device 21 via the positive electrode line PL.

  The power supply device 21 can supply DC power to the assembled battery 10 at a constant current (charging current). That is, the power supply device 21 can perform constant current charging of the assembled battery 10. The current value (constant value) when charging the assembled battery 10 using the power supply device 21 can be set as appropriate.

  Here, as the current rate at the time of charging is increased, the time for charging the assembled battery 10 can be shortened. On the other hand, as the current rate at the time of charging is increased, the internal resistance of the unit cell 11 may be increased with the uneven salt concentration inside the unit cell 11. In consideration of this point, the current value when charging the assembled battery 10 can be set.

  On the other hand, the negative electrode terminal of the assembled battery 10 is connected to the charge inspection machine 20 via the negative electrode line NL. Specifically, the negative electrode terminal of the battery pack 10 is connected to the power supply device 21 via the negative electrode line NL.

  The charging tester 20 has a voltage sensor 22. The voltage sensor 22 is connected to the positive terminal and the negative terminal of the assembled battery 10 and detects the voltage between the terminals of the assembled battery 10. The charging tester 20 has a controller 24, and the detection result of the voltage sensor 22 is output to the controller 24.

  Moreover, the charge inspection machine 20 has the current sensor 23, and the current sensor 23 is provided in the positive electrode line PL. When the battery pack 10 is charged using the power supply device 21, the current sensor 23 detects the value of the current flowing through the battery pack 10 and outputs the detection result to the controller 24.

  In the present embodiment, the current sensor 23 is provided in the positive electrode line PL, but is not limited thereto. That is, the current sensor 23 only needs to detect the value of the current flowing through the assembled battery 10 when charging the assembled battery 10. For this reason, the current sensor 23 can be provided in either the positive electrode line PL or the negative electrode line NL.

  In the present embodiment, the charging tester 20 is connected to the assembled battery 10, but the present invention is not limited to this. That is, the charge inspection machine 20 may be connected to the inspection object. For example, when inspecting the unit cell 11, the charge inspection machine 20 can be connected to the positive terminal and the negative terminal of the unit cell 11. Moreover, when comprising one battery module using the several cell 11, the charge tester 20 can be connected with respect to the positive electrode terminal and negative electrode terminal of a battery module.

  Next, operation | movement of the charge inspection machine 20 in a present Example is demonstrated using the flowchart shown in FIG. The process shown in FIG. 2 is a process for charging the assembled battery 10 and calculating the SOC of the assembled battery 10 after charging. The process shown in FIG. 2 is executed by the controller 24.

  In step S <b> 101, the controller 24 detects the voltage value Vs of the assembled battery 10 using the voltage sensor 22. Information regarding the voltage value Vs can be stored in a memory. Here, when the process shown in FIG. 2 is started, the assembled battery 10 is left unattended, and the polarization of the assembled battery 10 is eliminated. For this reason, the voltage value (CCV) Vs detected by the voltage sensor 22 can be regarded as the OCV of the assembled battery 10.

  In step S <b> 102, the controller 24 starts charging the assembled battery 10 using the power supply device 21. Here, the battery pack 10 is charged under a constant current. When the charging of the assembled battery 10 is started, the voltage value of the assembled battery 10 rises by the amount of polarization as polarization occurs in the assembled battery 10. Moreover, the controller 24 starts measurement of time t1 using a timer, when charging of the assembled battery 10 is started. The measurement time t1 is the time from when charging of the assembled battery 10 is started until now.

  In step S103, the controller 24 determines whether or not the measurement time t1 using the timer has reached a predetermined time t_th. The predetermined time t_th is a time corresponding to half of the time until the battery pack 10 is completely charged.

  In the charging inspection machine 20 of the present embodiment, the charging process of the assembled battery 10 is completed after increasing the SOC of the assembled battery 10 by a predetermined amount. Here, since charging of the assembled battery 10 is performed at a constant current, the time for completing the charging process of the assembled battery 10 is known based on the charging current value. That is, the value obtained by integrating the charging current value for the charging time is the amount of increase in the SOC, so if the amount of increase in the SOC and the charging current value are determined in advance, the time until the charging process is completed is specified. can do.

  When the measurement time t1 reaches the predetermined time t_th, the controller 24 performs the process of step S104. On the other hand, when the measurement time t1 has not reached the predetermined time t_th, the controller 24 continues charging the assembled battery 10.

  In step S104, the controller 24 uses the voltage sensor 22 to detect the voltage value Vm ′ of the assembled battery 10 when the measurement time t1 reaches the predetermined time t_th. Information on the voltage value Vm ′ can be stored in a memory.

  Here, the voltage value Vm ′ is higher than the OCV of the assembled battery 10 when the measurement time t1 reaches the predetermined time t_th by the amount of voltage increase associated with the polarization of the assembled battery 10. When the voltage value Vm ′ of the assembled battery 10 is detected, the controller 24 starts measuring the time t2 using a timer. The measurement time t2 is a time from when the voltage value Vm ′ of the assembled battery 10 is detected to the present time.

  In step S105, the controller 24 determines whether or not the measurement time t2 using the timer has reached a predetermined time t_th. Here, the predetermined time t_th is the same as the predetermined time t_th used in the process of step S103. That is, the predetermined time t_th is a time corresponding to half of the time until the battery pack 10 is completely charged.

  When the measurement time t2 reaches the predetermined time t_th, the controller 24 performs the process of step S106. On the other hand, when the measurement time t2 has not reached the predetermined time t_th, the controller 24 continues charging the assembled battery 10.

  In step S <b> 106, the controller 24 stops the charging of the assembled battery 10 and detects the voltage value Ve ′ of the assembled battery 10 using the voltage sensor 22. Information regarding the voltage value Ve ′ can be stored in a memory. The voltage value Ve ′ is a voltage value (CCV) immediately after the charging of the assembled battery 10 is stopped. For this reason, the voltage value Ve ′ includes a voltage change amount associated with the polarization of the battery pack 10.

  In step S107, the controller 24 uses the voltage value Vs detected in the process of step S101, the voltage value Vm ′ detected in the process of step S104, and the voltage value Ve ′ detected in the process of step S106. The voltage drop amount ΔVd of the assembled battery 10 is calculated.

  Specifically, the controller 24 can calculate the voltage drop amount ΔVd based on the following formula (1). The voltage drop amount ΔVd is a voltage drop amount that is generated along with the elimination of polarization after the charging of the assembled battery 10 is stopped.

  In step S108, the controller 24 calculates the SOC of the battery pack 10 using the voltage drop amount ΔVd calculated in the process of step S107. Here, if the voltage drop amount ΔVd can be calculated, the OCV of the battery pack 10 can be calculated by subtracting the voltage drop amount ΔVd from the voltage value Ve ′ when charging of the battery pack 10 is stopped. If the OCV of the assembled battery 10 can be calculated, the SOC of the assembled battery 10 can be calculated (estimated) by using the correspondence relationship between the OCV and the SOC.

  Here, the meaning of the formula (1) will be described with reference to FIG. In FIG. 3, the horizontal axis represents time (charging time), and the vertical axis represents the voltage value (CCV) of the assembled battery 10 detected by the voltage sensor 22. A solid line L1 illustrated in FIG. 3 indicates the behavior of the voltage value (CCV) of the assembled battery 10 while the assembled battery 10 is being charged.

  In FIG. 3, ts, tm, and te indicate timings when the voltage values Vs, Vm ′, and Ve ′ are detected, respectively. The voltage value Vm indicates an OCV corresponding to the voltage value (CCV) Vm ′, and when the battery pack 10 is charged, the voltage value Vm is lower than the voltage value Vm ′. The voltage value Ve indicates an OCV corresponding to the voltage value (CCV) Ve ′. When the assembled battery 10 is charged, the voltage value Ve is lower than the voltage value Ve ′.

  In the present embodiment, since the assembled battery 10 is charged with a constant current, it can be considered that the polarization component generated by charging / discharging the assembled battery 10 is equal to the polarization component that is eliminated by leaving the assembled battery 10 unattended. In this case, the voltage increase amount ΔVu immediately after starting the charging of the assembled battery 10 becomes equal to the voltage decrease amount ΔVd after stopping the charging of the assembled battery 10.

  When the voltage rise amount ΔVu and the voltage drop amount ΔVd are equal, the slope of the solid line L1 is equal to the slope of the alternate long and short dash line L2 shown in FIG. Here, the inclination of the solid line L1 is an inclination in an area of the solid line L1 excluding an area where the voltage changes with polarization. The alternate long and short dash line L2 indicates the behavior of the voltage value when the voltage increase amount ΔVu and the voltage drop amount ΔVd are not taken into consideration. That is, the alternate long and short dash line L2 indicates the OCV behavior of the battery pack 10.

  In FIG. 3, the interval between timings ts and tm (predetermined time t_th) is equal to the interval between timings tm and te (predetermined time t_th). The assembled battery 10 is charged with a constant current. Therefore, the voltage difference between the voltage values Ve and Vm is equal to the voltage difference between the voltage values Vm and Vs. Thereby, the voltage value Ve is represented by the following formula (2).

  Here, since the voltage value Ve is a value obtained by subtracting the voltage drop amount ΔVd from the voltage value Ve ′, the above equation (2) is expressed by the following equation (3).

  Here, since the voltage value Vm is a value obtained by subtracting the voltage increase amount ΔVu from the voltage value Vm ′, the above equation (3) is expressed by the following equation (4).

  Since it is assumed that the voltage drop amount ΔVd and the voltage rise amount ΔVu are equal to each other, the above equation (4) is expressed by the following equation (5).

  If the formula (5) is modified, the formula (1) is obtained.

  In the above formula (1), the voltage values Ve ′, Vm ′, and Vs can be detected by the voltage sensor 22. Therefore, the controller 24 can calculate the voltage drop amount ΔVd by substituting the voltage values Ve ′, Vm ′, and Vs acquired from the voltage sensor 22 into the above equation (1). If the voltage drop amount ΔVd can be calculated, the voltage value Ve representing the OCV of the assembled battery 10 can be calculated by subtracting the voltage drop amount ΔVd from the voltage value Ve ′.

  If the assembled battery 10 is left after the assembled battery 10 is stopped being charged, the polarization of the assembled battery 10 can be eliminated, and the voltage value (OCV) Ve of the assembled battery 10 can be detected. However, in this case, the assembled battery 10 must be left until the polarization of the assembled battery 10 is eliminated, and the time until the voltage value (OCV) Ve of the assembled battery 10 is detected, in other words, the assembled battery 10 The time for inspecting the battery 10 is extended.

  According to the present embodiment, as described above, the voltage value (OCV) Ve of the assembled battery 10 is calculated only by detecting the voltage values Ve ′, Vm ′, and Vs that can be acquired during charging of the assembled battery 10. Can do. Thereby, it is not necessary to leave the assembled battery 10 until the polarization of the assembled battery 10 is eliminated. If the time for leaving the assembled battery 10 is omitted, the time for inspecting the assembled battery 10 can be shortened.

  In this embodiment, the voltage value Vm ′ is detected at the timing tm located between the timings ts and te, but the present invention is not limited to this. Specifically, the interval between the timings ts and te is equally divided into three or more times, and the voltage value of the assembled battery 10 can be detected at an arbitrary timing when the division is performed. FIG. 4 shows a state where the intervals between the timings ts and te are equally divided into three intervals Δt. In the example shown in FIG. 4, the voltage value of the assembled battery 10 can be detected at either timing tm1 or tm2.

  In the case shown in FIG. 4, the voltage drop amount ΔVd can be calculated based on the following equation (6).

  In the above equation (6), Vm2 ′ is a voltage value detected by the voltage sensor 22 at the timing tm2. Here, in the above formula (6), the voltage difference represented by “Ve′−Vm2 ′” is calculated, but the present invention is not limited to this. Specifically, the voltage difference “Vm2′−Vm1 ′” can be used instead of the voltage difference “Ve′−Vm2 ′”.

  Here, the voltage value Vm1 'is a voltage value detected by the voltage sensor 22 at the timing tm1. The voltage difference “Vm1′−Vs” cannot be used in place of the voltage difference “Ve′−Vm2 ′”. In the process in which the voltage value of the assembled battery 10 increases from the voltage value Vs to the voltage value Vm1 ′, a voltage increase amount due to polarization occurs, and thus the voltage difference “Vm1′−Vs” cannot be used.

  As described above, when the interval between the timings ts and te is equally divided into the three intervals Δt, the voltage drop amount ΔVd can be calculated based on the above equation (6). Here, based on the same concept, when the interval between the timings ts and te is equally divided into a plurality of intervals Δt, the voltage drop amount ΔVd can be calculated based on the following equation (7).

  In the above equation (7), k is a number (an integer of 2 or more) obtained by dividing the interval between the timings ts and te evenly. Vm (k−1) ′ is a voltage value detected by the voltage sensor 22 at the timing tm (k−1). When the interval between the timings ts and te is evenly divided by the division number k, timings tm1 to tm (k−1) are generated between the timings ts and te.

  As in the case described in the above formula (6), instead of the voltage difference “Ve′−Vm (k−1) ′” shown in the above formula (7), the voltage values detected at other timings Differences can be used. However, the voltage difference based on the voltage value Vs cannot be used in place of the voltage difference “Ve′−Vm (k−1) ′” shown in the above equation (7).

  On the other hand, when calculating the voltage drop amount ΔVd, the voltage drop amount ΔVd can be corrected in consideration of the temperature of the assembled battery 10. When the SOC of the assembled battery 10 is a predetermined value, the voltage drop amount ΔVd and the temperature of the assembled battery 10 have, for example, the relationship shown in FIG. In FIG. 5, the horizontal axis indicates the temperature of the assembled battery 10, and the vertical axis indicates the voltage drop amount ΔVd. The relationship shown in FIG. 5 can be obtained by conducting an experiment in advance.

  As shown in FIG. 5, the voltage drop amount ΔVd tends to decrease as the temperature of the assembled battery 10 increases. In other words, the voltage drop amount ΔVd is likely to increase as the temperature of the battery pack 10 decreases. The voltage drop amount ΔVd depends on the internal resistance of the battery pack 10. Here, since the internal resistance of the assembled battery 10 tends to decrease as the temperature of the assembled battery 10 increases, the voltage drop amount ΔVd also tends to decrease. Moreover, since the internal resistance of the assembled battery 10 is likely to increase as the temperature of the assembled battery 10 decreases, the voltage drop amount ΔVd also tends to increase.

  A method of correcting the voltage drop amount ΔVd will be described with reference to FIG. First, the temperature Ts of the assembled battery 10 when charging of the assembled battery 10 is started is detected. Here, the temperature of the assembled battery 10 can be detected using a temperature sensor. Further, the temperature Te of the assembled battery 10 when the charging of the assembled battery 10 is stopped is detected.

  Next, by using the relationship shown in FIG. 5, voltage drop amounts ΔVd (Ts) and ΔVd (Te) corresponding to the temperatures Ts and Te are calculated. Here, the difference between the voltage drop amount ΔVd (Ts) and the voltage drop amount ΔVd (Te) is a correction value of the voltage drop amount ΔVd. Therefore, the corrected voltage drop amount ΔVd is calculated by adding a correction value (ΔVd (Ts) −ΔVd (Te)) to the voltage drop amount ΔVd calculated by the processing shown in FIG. Can do.

  Thus, the accuracy of the voltage drop amount ΔVd can be improved by considering the temperature of the assembled battery 10. Further, if the accuracy of the voltage drop amount ΔVd is improved, the OCV and SOC of the assembled battery 10 after the charging is stopped can be accurately estimated.

  In this embodiment, the voltage drop amount ΔVd is calculated based on the above formula (1), and the voltage value (OCV) of the assembled battery 10 when charging of the assembled battery 10 is stopped based on the voltage drop amount ΔVd. Although Ve is calculated, the present invention is not limited to this.

  For example, if the voltage increase amount ΔVu after starting charging of the assembled battery 10 can be detected, the voltage value of the assembled battery 10 is subtracted from the voltage value Ve ′ after stopping charging. (OCV) Ve can be calculated.

  As shown in FIG. 3, after the voltage value of the assembled battery 10 increases by the voltage increase amount ΔVu, the voltage value of the assembled battery 10 increases at a constant rate of change. That is, the rate of change of the voltage increase amount ΔVu is different from the rate of change of the voltage value of the assembled battery 10 after the occurrence of polarization.

  Therefore, if the amount of change in the voltage value of the assembled battery 10 is detected between the start of charging of the assembled battery 10 and the change rate of the voltage value changing, the voltage increase amount ΔVu can be specified. . Specifically, if the difference between the voltage value of the assembled battery 10 when charging is started and the voltage value of the assembled battery 10 when the change rate of the voltage value changes is calculated, it accompanies the polarization of the assembled battery 10. The voltage increase amount ΔVu can be specified.

  As described above, when the assembled battery 10 is charged with a constant current, the voltage increase amount ΔVu and the voltage decrease amount ΔVd become equal to each other. Therefore, the assembled battery 10 after charging is stopped by detecting the voltage increase amount ΔVu. The voltage value (OCV) of the battery 10 can be calculated.

  In this embodiment, when the assembled battery 10 is inspected, the voltage value (OCV) Ve of the assembled battery 10 is calculated. However, the present invention is not limited to this. For example, in a vehicle on which the assembled battery 10 is mounted, the assembled battery 10 can be charged using an external power supply (commercial power supply). Such charging is called external charging. When performing external charging, a charger for converting AC power supplied from an external power source into DC power is used.

  Usually, since external charging is performed at a constant current, the OCV of the assembled battery 10 when external charging is completed can be calculated by using the same method as in the present embodiment. Thereby, when performing external charging, OCV and SOC of the assembled battery 10 can be calculated according to completion of external charging.

10: assembled battery (power storage device), 11: single battery (power storage device),
20: Charge inspection machine (charging system), 21: Power supply device, 22: Voltage sensor,
23: Current sensor, 24: Controller, PL: Positive line, NL: Negative line

Claims (7)

A voltage sensor for detecting the voltage of the power storage device for charging and discharging;
A controller that charges the power storage device for a predetermined time at a constant current;
The controller subtracts the amount of change in the voltage of the power storage device after the voltage increase due to polarization from the amount of change in the voltage of the power storage device between the start and end of the charging. A charging system that calculates a voltage drop amount after the charging is finished. The controller calculates the voltage drop amount based on the following formula (I):

Here, ΔVd represents the voltage drop amount, Vs represents the voltage of the power storage device at the start timing of charging, Ve ′ represents the voltage of the power storage device at the end timing of charging, and Vm ′. Is a voltage of the power storage device at a timing located in the center between the start timing and the end timing,
The charging system according to claim 1.   The controller calculates an open circuit voltage of the power storage device when the charging is finished by subtracting the voltage drop amount from a closed circuit voltage of the power storage device when the charging is finished. The charging system according to claim 1 or 2.   The charging system according to claim 3, wherein the controller specifies a charging state corresponding to the calculated open circuit voltage using a correspondence relationship between the open circuit voltage and the charging state. It has a temperature sensor that detects the temperature of the power storage device,
The controller is
Using the correspondence relationship between the temperature of the power storage device and the amount of voltage drop, calculate the amount of change in the voltage drop corresponding to the temperature change of the power storage device accompanying the charging,
The charging system according to claim 1, wherein the calculated voltage drop amount is corrected using the change amount. Charging the power storage device for a predetermined time at a constant current; and
Detecting the voltage of the power storage device;
By subtracting the amount of change in the voltage of the power storage device after a voltage increase due to polarization from the amount of change in the voltage of the power storage device between the start and end of the charge, the charge is Calculating the amount of voltage drop after completion;
A voltage drop amount calculation method characterized by comprising: The voltage drop amount is calculated based on the following formula (II).

Here, ΔVd represents the voltage drop amount, Vs represents the voltage of the power storage device at the start timing of charging, Ve ′ represents the voltage of the power storage device at the end timing of charging, and Vm ′. Is a voltage of the power storage device at a timing located in the center between the start timing and the end timing,
The voltage drop amount calculation method according to claim 6.