KR20130028664A - State controlling apparatus, equalization of electrical storage device - Google Patents

Abstract

Provided is a technique for uniformly charging a plurality of secondary batteries.
The BMS 20 is an apparatus for managing the state of a plurality of secondary batteries 50 connected in series, including: a voltmeter 24 for individually measuring the voltage value V of the secondary battery 50; After the time change rate of the voltage value V of one of the secondary batteries 50 reaches the reference value K, the time change rate of the voltage value V of the other secondary battery 50 reaches the reference value K. A time measuring unit 42 for measuring a time difference until reaching; A discharge circuit 26 for separately discharging the secondary batteries 50; And an equalization control section 44 that controls the discharge circuit 26 using the time difference. According to the BMS 20, even when the SOC charged in the power storage element cannot be equalized by the voltage value of the power storage element, the SOC charged in the power storage element can be equalized according to the rate of change of the voltage of the power storage element.

Description

How to equalize state management devices and power storage devices {STATE CONTROLLING APPARATUS, EQUALIZATION OF ELECTRICAL STORAGE DEVICE}

The invention disclosed herein relates to a technique for equalizing the capacitance charged and discharged in a plurality of power storage elements.

Conventionally, the electrical storage element which can be used repeatedly is used. The storage element can be used any number of times by repeating charging and discharging, and is more environmentally friendly than a battery that cannot be charged and discharged, and is currently expanding its field of use, such as an electric vehicle.

In an apparatus in which a plurality of power storage elements are used, the capacity of the power storage element may be uneven due to unevenness of the initial capacity or deterioration rate of each power storage element. If the capacity of the power storage element becomes uneven, at the time of charging, the voltage of one or several power storage elements is advanced or delayed before other power storage elements to reach the full charge voltage, so that charging is terminated, and all the power storage elements can be sufficiently charged. There may not be. At the time of discharge, the voltage of one or several power storage elements has reached or reached the discharge end voltage in advance of or before other power storage elements, and thus the discharge is terminated. have. In this manner, when the capacity of the power storage element becomes uneven, the capacity of the power storage element cannot be taken out to the maximum. Background Art Conventionally, a technique has been known in which a secondary battery having an uneven capacity is discharged using a discharge circuit such as a resistor to equalize the capacity of the secondary battery (for example, Patent Document 1). In this technique, the capacity of the secondary battery is equalized by obtaining the remaining energy capacity of the secondary battery from the voltage information of the secondary battery obtained in the non-current state and discharging each secondary battery based on the capacity difference.

Patent Document 1: Japanese Unexamined Patent Publication No. 2011-19329

Recently, olivine iron-based lithium ion secondary batteries (hereinafter, olivine iron-based batteries) have attracted attention as secondary batteries of electric vehicles and the like. An olivine iron battery is a kind of lithium ion battery, and an olivine-type iron phosphate is used for a positive electrode (positive electrode), and a graphite type material etc. are used for a negative electrode (negative electrode), for example. Therefore, in the olivine iron-based battery, there is no need to use a cobalt-based electrode material as the electrode, and there is an advantage of low cost and high safety as compared with a secondary battery using a cobalt-based electrode material.

The olivine iron-based battery has a region (hereinafter referred to as a change region) in which the voltage rapidly increases with respect to the increase in the remaining capacity. For example, when the graphite-based material is used as the negative electrode, the residual capacity of the secondary battery is reduced. It is known that it becomes a change area in the area | region whose SOC to show is 10% or less, and the area | region which is 90% or more. If the change area is in a region where the SOC is relatively high or the SOC is relatively low, even if an attempt is made to equalize the capacitance of the power storage element from the voltage information of the power storage element in the change region, the SOC of the power storage element is equalized before the capacity of the power storage element is equalized. About 100% or about 0% is reached, and charging / discharging of a power storage element is complete | finished. When the charge / discharge of the power storage element ends, the equalization of the capacity of the power storage element also ends, so it is difficult to fully equalize the capacity of the power storage element. Therefore, a technique for equalizing the capacitance of the power storage element using an area other than the change area is required.

On the other hand, the olivine iron-based battery has a planar region in combination with the negative electrode, for example, when a graphite-based material is used as the negative electrode, the SOC representing the remaining capacity of the secondary battery is 10% to 90%. It is known to have a flat area that extends over%. Here, the flat region means a region where the voltage of the secondary battery is substantially constant even if the SOC of the secondary battery is changed. Therefore, in a power storage element such as a secondary battery having a flat region, it is difficult to estimate the capacity of the power storage element from the voltage information of the power storage element acquired in this flat region during charging, and it is difficult to equalize the capacity of the power storage element.

In this specification, a technique of equalizing a capacity charged in a plurality of power storage elements is disclosed.

The state management apparatus disclosed in this specification is a state management apparatus which manages the state of the some electrical storage element connected in series, Comprising: The voltage measuring part which measures the voltage of each electrical storage element individually; A time measuring unit for measuring a time difference from when the time change rate of the voltage of one power storage element reaches a reference value, and then until the time change rate of the voltage of another power storage element reaches a reference value; A discharge unit for discharging the respective power storage elements individually; And an equalization control unit controlling the discharge unit using the time difference.

In this state management device, the voltage of each power storage element is measured, and the discharge of each power storage element is controlled using the time difference until the time change rate of the said voltage reaches a reference value. According to this state management device, even when the power storage element has a flat area and it is difficult to control equalization according to the voltage, the discharge can be controlled in accordance with the rate of change of the voltage of the power storage element, and the battery is charged and discharged. The dose can be equalized.

In the state management apparatus, the plurality of power storage elements include a first power storage element and a second power storage element, and the equalization control unit performs the second power storage element after the rate of change of time of the first power storage element reaches a reference value. It is good also as a structure which acquires the 1st time difference until a time change rate reaches a reference value, and has a reference time. When the plurality of power storage elements are being charged and the first time difference is greater than or equal to the reference time, the first power storage element is discharged using the first time difference, and the first time difference is less than the reference time. It is good also as a structure which does not discharge a 1st power storage element and a said 2nd power storage element, and when the said some power storage element is discharging and the said 1st time difference is more than the said reference time, the said 2nd power storage using a said 1st time difference When the element is discharged and the first time difference is less than the reference time, the first power storage element and the second power storage element may not be discharged.

In this state management apparatus, when a 1st time difference is more than a reference time, a 1st electrical storage element or a 2nd electrical storage element is discharged. In general, the difference in arrival time indicating the time from when the power storage element starts charging or discharging until reaching a constant state indicates a difference in capacity of the power storage element due to deterioration.

According to this state management apparatus, when the 1st time difference which is the difference of arrival time is more than a reference time, the 1st electrical storage element or a 2nd electrical storage element is discharged, and the difference of the capacitance charged and discharged in a 1st electrical storage element and a 2nd electrical storage element is made. It can be kept constant within a constant capacity difference corresponding to a reference time.

The state management apparatus further includes a deterioration determining unit that determines deterioration of the power storage element, wherein the deterioration determination unit is charging the plurality of power storage elements, and a time change rate of the voltage of the second power storage element reaches the reference value. In the case where the charging of the plurality of power storage elements is completed before the charging of the second power storage element is completed, the configuration may be determined that the second power storage element is deteriorated, and the plurality of power storage elements are being discharged. A configuration in which the first power storage element is deteriorated when the discharge of the plurality of power storage elements is completed and the discharge of the second power storage element is completed before the time change rate of the voltage of the second power storage element reaches the reference value. You may make it.

When charging the power storage element, when the charge of the first power storage element is terminated before the time change rate of the voltage of the second power storage element changes beyond the reference value, the capacity of the first power storage element and the second power storage element due to deterioration. It can be seen that the difference is more than a constant capacity difference corresponding to the reference time. In the case of discharging the power storage element, when the discharge of the first power storage element is terminated before the time change rate of the voltage of the second power storage element changes beyond the reference value, the first power storage element and the second power storage element and It can be seen that the dose difference of is different from the constant dose difference corresponding to the reference time. According to this state management device, it is judged that the first power storage element or the second power storage element is deteriorated in the above-described case, so that the plurality of power storage elements, such as equalizing the capacity of the power storage element and prohibiting the use of the plurality of power storage elements, are used. Take the necessary measures.

The state management apparatus further includes a deterioration determining unit that determines deterioration of the power storage element, wherein the deterioration determination unit is charging the plurality of power storage elements, and a time change rate of the voltage of the second power storage element reaches the reference value. Before the above, when the elapsed time after the time change rate of the voltage of the first power storage element reaches the reference value reaches the prescribed time, it may be configured to determine that the second power storage element is deteriorated, the plurality of power storage elements Is discharged, and when the elapsed time after the time change rate of the voltage of the first power storage element reaches the reference value reaches the prescribed time before the time change rate of the voltage of the second power storage element reaches the reference value, It is good also as a structure which judges that a single electrical storage element is deteriorated.

When the elapsed time after the time change rate of the voltage of the first power storage element reaches the reference value reaches the prescribed time before the time change rate of the voltage of the second power storage element changes beyond the reference value, charging of the second power storage element occurs due to deterioration. It can be seen that the time is prolonged or the discharge time of the first power storage element is shortened, so that the rate of change of the voltage of the second power storage element does not reach the reference value within the prescribed time. According to this state management device, it is judged that the first power storage element or the second power storage element is deteriorated in the above-described case, so that the plurality of power storage elements, such as equalizing the capacity of the power storage element and prohibiting the use of the plurality of power storage elements, are used. Take the necessary measures.

In the state management apparatus, the equalization control unit may be configured to set a discharge time for discharging the first power storage element or the second power storage element using the first time difference. According to the state management device, the first power storage device or the second power storage device is used by using the capacity difference between the capacity charged and discharged in the first secondary battery corresponding to the first time difference and the capacity charged and discharged in the second secondary battery. Since the discharge time for discharging is set, the capacitance charged and discharged to the first power storage element and the second power storage element can be equalized.

In the state management apparatus, when the voltage of the power storage element reaches a reference voltage and the time change rate of the voltage of the power storage element reaches a reference value, the time change rate of the voltage of the power storage element is It is good also as a structure which judges that the reference value was reached. According to this state management device, in addition to the time change rate of the voltage of the power storage element, the discharge is controlled based on the voltage of the power storage element. For example, when the time change rate reaches the reference value a plurality of times, A specific one can be selected from a plurality of times, and the capacity charged and discharged to the plurality of power storage elements can be equalized with good accuracy.

In the state management apparatus, the power storage element may be configured to be constant current charged or constant current discharged. According to this state management device, since the power storage element is charged and discharged with a constant current, it is easy to correspond the time difference and the capacitance difference of the power storage element, and to easily equalize the capacity charged and discharged to the power storage element.

In the said state management apparatus, the charge / discharge rate of the said electrical storage element may be set as the structure set to 1C or less, More preferably, it is good also as a structure set to less than 0.9C. When the power storage element is charged and discharged with a constant current, the lower the charge / discharge rate, the greater the rate of change in the voltage of the power storage element during charge and discharge. According to this state management device, since the charge / discharge rate is set relatively low, it is easy to detect the time change rate of the power storage element and to easily acquire the time difference.

In the state management apparatus, the cathode of the power storage element may be formed of a graphite-based material. The power storage element in which the cathode is formed of a graphite material includes a change point at which the rate of change of the power storage element is larger than other regions. According to this state management apparatus, it is easy to detect the time change rate of an electrical storage element using the said inflection point, and is easy to acquire a time difference.

In the state management apparatus, each of the power storage elements may be an olivine iron-based lithium ion secondary battery. In an olivine iron-based lithium ion secondary battery, the SOC has a flat region that is widened from 10% to 90%, and in the flat region, it is difficult to estimate the SOC value of the power storage element based on the voltage value of the power storage element. . In this state management device, since the SOC value of the power storage element is estimated based on the time change rate of the voltage of the power storage element, the capacity charged and discharged in the power storage element can be equalized even in the flat region.

The state management device disclosed in the present specification further includes a state management device for managing a state of a plurality of power storage elements connected in series, the voltage management unit measuring voltages of each power storage element individually; A discharge unit for discharging the respective power storage elements individually; A storage unit in which discharge time is stored in correspondence with the order in which the time change rate of the voltage of each power storage element reaches a reference value; And an equalization control unit for controlling the discharge unit, wherein the equalization control unit is configured to discharge the power storage element over the discharge time stored in correspondence with the order in which the time change rate of the voltage of each power storage element reaches the reference value. You may make it.

In this state management apparatus, the voltage of each power storage element is measured, and the discharge of each power storage element is controlled using the rank which the rate of time change of the said voltage reaches a reference value. According to this state management device, even when the power storage element has a flat area and it is difficult to control equalization based on the voltage, the discharge can be controlled based on the time change rate of the voltage of the power storage element, and the power storage element is charged. The discharged capacity can be equalized. In setting the discharge time, the discharge time can be set using the discharge time stored in the storage unit in advance, and the discharge time can be set early.

The state management device disclosed in the present specification further includes a state management device for managing a state of a plurality of power storage elements connected in series, the voltage management unit measuring voltages of each power storage element individually; A discharge unit for discharging the respective power storage elements individually; And an equalization control unit for controlling the discharge unit. The equalization control unit may be configured to start discharging the power storage element when the rate of change of the voltage of each power storage element reaches a reference value.

In this state management device, the voltage of each power storage element is measured, and when the time change rate of the voltage reaches a reference value, the power storage element is discharged. According to this state management device, even when the power storage element has a flat area and it is difficult to control equalization based on the voltage, the discharge can be controlled based on the time change rate of the voltage of the power storage element, so that the power storage element is charged. The discharged capacity can be equalized. In addition, since the discharge of the power storage element is started when the rate of change of the voltage of the power storage element reaches a reference value, the discharge start time of the power storage element can be advanced.

The present invention is also implemented in an equalization method of a power storage element realized using the state management apparatus. The equalization method of the power storage element disclosed in the present specification includes a voltage measuring step of individually measuring a voltage of each power storage element during charging and discharging, the method of equalizing the power storage element equalizing a state of a plurality of power storage elements connected in series; A time measurement step of measuring a time difference from when the time change rate of the voltage of one power storage element reaches a reference value, and then until the time change rate of the voltage of another power storage element reaches a reference value; And a discharge step of individually discharging each of the power storage elements using the time difference.

Moreover, the equalization method of the electrical storage element disclosed by this specification is a equalization method of the electrical storage element which equalizes the state of the some electrical storage element connected in series, The voltage measuring step of measuring the voltage of each electrical storage element during charge / discharge separately. Wow; And a discharge step of discharging each of the power storage elements individually, wherein in the discharge step, the power storage element is discharged over a preset discharge time corresponding to a ranking in which a time change rate of the voltage of each power storage element reaches the reference value. A configuration may be employed.

Moreover, the equalization method of the electrical storage element disclosed by this specification is a equalization method of the electrical storage element which equalizes the state of the some electrical storage element connected in series, The voltage measuring step of measuring the voltage of each electrical storage element during charge / discharge separately. Wow; A discharge step of discharging the respective power storage elements individually may be included, and in the discharge step, the discharge of the power storage element may be started when the rate of change of the voltage of each power storage element reaches the reference value.

According to the present invention, it is possible to equalize the capacitances charged and discharged in a plurality of power storage elements.

1 is a block diagram of a charging system (discharge system).
2 is a schematic diagram of a discharge circuit.
3 is a flowchart showing an equalization process of the first embodiment.
4 is a view showing charge and discharge characteristics of a secondary battery.
5 is a view showing charge and discharge characteristics of a secondary battery.
6 is a view showing charge and discharge characteristics of a secondary battery.
7 is a flowchart showing the equalization process of the second embodiment.
8 is a flowchart showing an equalization process of the third embodiment.
9 is a flowchart showing an equalization process of the fourth embodiment.
10 is a flowchart showing an equalization process of another embodiment.

≪ Example 1 >

EMBODIMENT OF THE INVENTION Hereinafter, Example 1 of this invention is described using FIGS.

1. Configuration of the state judgment device

1 is a diagram showing the configuration of a charging system (discharge system) 10 of the present embodiment. The charging system (discharge system) 10 is comprised by the battery group 12, the state management apparatus (hereinafter, BMS) 20, and the charger (load) 18. As shown in FIG. The battery group 12 is mounted in an electric vehicle and includes a plurality of secondary batteries 50 (an example of power storage element) connected in series therein. The battery group 12 is constant current charged by being connected to a charger 18 provided inside or outside of an electric vehicle, and is discharged by being connected to a load 18 such as a power source provided inside of the electric vehicle. The BMS 20 monitors the voltage value V, the current value I, and the like of each of the secondary batteries 50 of the battery group 12 during charging, indicating the charge and discharge state of the secondary battery 50. Manage SOC and equalize SOC.

In this embodiment, an example in which an olivine iron-based lithium ion secondary battery (hereinafter, an olivine iron-based battery) is used as the secondary battery 50 is shown. This secondary battery 50 is a type of lithium ion battery, in which an olivine-type iron phosphate is used for the positive electrode and a graphite material is used for the negative electrode. As shown in FIG. 4, the secondary battery 50 has a battery voltage with respect to an increase in SOC in an initial charge (end of discharge) having an SOC of less than 10% and an end of charge (end of discharge) having an SOC of 90% or more. Has a rapidly rising area. Further, in the charging medium period (during discharge) in which the SOC is 10% or more and less than 90%, the battery voltage has a substantially constant region (hereinafter, a flat region) with respect to the increase of the SOC.

The BMS 20 includes a central processing unit (hereinafter referred to as CPU) 30, an analog-to-digital converter (hereinafter referred to as an ADC) 34, an ammeter 22, a voltmeter (an example of a voltage measuring unit) 24, and a discharge circuit ( An example of a discharge portion) 26, and a thermometer 28.

The CPU 30 incorporates a memory (an example of a storage unit) 32 such as a ROM or a RAM, and various programs for controlling the operation of each configuration of the BMS 20 are stored in the memory 32. The CPU 30 functions as a time measurement section 42, an equalization control section 44, a deterioration determination section 46, and the like according to a program read from the memory 32, and includes a BMS 20 including a discharge circuit 26. Each part in () is controlled.

The thermometer 28 measures the temperature of the battery group 12 in a contact or non-contact manner and stores the measured temperature in the memory 32. As shown in FIG. 2, the voltmeter 24 is directly connected to both ends of each of the secondary batteries 50 through the wiring 54, and the voltage value V of the secondary battery 50 during charging and discharging is measured. Individual measurements are taken at regular (predetermined) time periods. The battery group 12 includes N (N: 2 or more) secondary batteries 50A, 50B,... 50N, and the voltmeter 24 includes the voltage VA of each secondary battery 50. , VB, ... VN) are measured, respectively. The voltmeter 24 transmits these measured voltage values V to the ADC 34.

In the wiring 54 connecting the secondary battery 50 and the voltmeter 24, a discharge circuit 26 for discharging the secondary battery 50 individually is provided.

As shown in FIG. 2, in the discharge circuit 26, discharge circuits 26A and 26B for discharging each secondary battery 50 between the wirings 54 connected to both ends of the respective secondary batteries 50. 26N) is provided. Each discharge circuit 26 is constituted by a resistor R and a switch Q. FIG. When the switch Q of the discharge circuit 26 is controlled to be opened and closed by the CPU 30 functioning as the equalization control section 44, and the switch Q is closed by the CPU 30, the wiring 54 And a current flows from the secondary battery 50 through the resistor R to discharge the corresponding secondary battery 50. When the switch Q is opened by the CPU 30, the discharge from the corresponding secondary battery 50 is stopped.

The ammeter 22 measures the current flowing in the wiring 52 connecting the battery group 12 and the charger 18, and measures the current value of the charge / discharge current ZI flowing in common to the secondary battery 50. Measure In addition, the ammeter 22 measures the current values IA, IB, ... IN of the currents (hereinafter, equalized discharge currents) HI discharged individually from the respective secondary batteries 50 through the wiring 54. Measure The ammeter 22 transmits these measured current values I to the ADC 34.

The ADC 34 is connected to the ammeter 22, the voltmeter 24, and the CPU 30, and includes the current value I and the voltage value V, which are analog data transmitted from the ammeter 22 and the voltmeter 24. ) Is converted into digital data, and the converted current value I and voltage value V are stored in the memory 32. The CPU 30 functioning as the time measuring unit 42 and the deterioration determining unit 46 or the like executes the equalization process described later using the current value I and the voltage value V stored in the memory 32. do.

2. Equalization Treatment

The equalization process performed by the BMS 20 at the time of charging the battery group 12 is demonstrated using FIG. 3 or FIG. In this embodiment, the battery group 12 is charged with constant current at low charge of 0.5C charge. The equalization process is performed in conjunction with the charge control process for the battery group 12. 3 shows a flowchart of the charge control process for the battery group 12 executed in the CPU 30.

When the battery group 12 is connected to the charger 18 by the user and the power supply from the charger 18 to the battery group 12 is started by the user, the CPU 30 executes the charge control process and the equalization process. do. When the CPU 30 starts the equalization process, the voltage value V of each secondary battery 50 is repeatedly measured at a predetermined time ΔX, and the difference value ΔV of the continuously measured voltage values V is measured. The time change rate DV of the voltage value V obtained by dividing the absolute value of) by the predetermined time ΔX is calculated. The CPU 30 detects that the calculated time change rate DV reaches the reference value K (K> 0) (S2: NO).

As described above, since the voltage value V of the secondary battery 50 is substantially constant with respect to the increase of the SOC, the voltage value V of the secondary battery 50 reaches the reference voltage value. Even if it is detected, the SOC of the secondary battery 50 cannot be estimated with good accuracy.

In this embodiment, as shown in FIG. 5, in the flat region of the olivine iron-based battery using the graphite-based material as the negative electrode, the rate of change in the time value of the voltage value V of the secondary battery 50 during charging is different. It is noted that there is a change point that becomes larger. In a battery using a graphite-based material as a negative electrode, there is a change point in which the rate of change of time is significantly changed compared with other ranges. In the olivine iron-based battery using the graphite-based material as the negative electrode, it was noted that the change point is located in the flat region. That is, in the olivine iron-based battery, two change points KS1 and KS2 exist in which the rate of change of time becomes larger than the reference value K in the flat region. In the following description, the case where the voltage value corresponding to a change point reaches the larger change point KS2 among these change points KS1 and KS2 is demonstrated. That is, the CPU 30 increases the voltage value V to the voltage value (an example of the reference voltage) KV2 corresponding to the change point KS2, and the time change rate DV reaches the reference value K. To detect that. And when the change point KS1 is reached, the same process may be performed.

When the CPU 30 detects that the time change rate DV of any of the secondary batteries 50 reaches the reference value K (S2: YES), the CPU 30 starts to measure the time since the arrival (S2: YES) ( S4). The CPU 30 functioning as the time measuring unit 42 has a time change rate DV of the other secondary battery 50 after the time change rate DV of the one secondary battery 50 reaches the reference value K. Elapsed time (an example of time difference) DELTA T until) reaches the reference value K, and the elapsed time DELTA T is compared with the reference time KT stored in the memory 32 ( S6).

In the following description, for the sake of understanding, the secondary battery 50 in which the time-varying rate DV reached the reference value K is called the first secondary battery 50, among other secondary batteries 50. One is called the 2nd secondary battery 50, and the equalization process in the 1st secondary battery 50 and the 2nd secondary battery 50 is demonstrated. That is, in the first secondary battery 50, the voltage value V rises (ie, SOC is large) to the change point KS2 as soon as possible among the plurality of secondary batteries 50. The battery 50 assumes that the voltage value V increases (that is, the SOC is small) to the latest change point KS2 among the plurality of secondary batteries 50.

As shown in FIG. 6, the time change rate of the first secondary battery 50 is referred to as time change rate DV1, the time change rate of second secondary battery 50 is referred to as time change rate DV2, and the time change rate DV1 is a reference value. The elapsed time from reaching (K) until the time change rate DV2 reaches the reference value K is referred to as elapsed time (an example of the first time difference) ΔT1. In addition, in the following description, all the secondary batteries 50 which exist in multiple numbers are demonstrated by applying the 1st secondary battery 50 to each secondary battery 50 other than the 2nd secondary battery 50. FIG. can do.

When the time change rate DV2 reaches the reference value K and the elapsed time ΔT1 becomes less than the reference time KT before the reference time KT elapses (S6: NO), the CPU 30 It is determined that the first secondary battery 50 and the second secondary battery 50 are evenly charged. In this case, the CPU 30 ends the equalization process without discharging any secondary batteries 50.

On the other hand, when the time change rate DV2 does not reach the reference value K and the elapsed time ΔT1 is equal to or greater than the reference time KT before the reference time KT elapses (S6). : YES), while monitoring the time-variation rate DV2 reaching the reference value K, the total voltage, which is the sum of the voltage values V of the secondary battery 50, increases to reach the end-of-charge voltage. To monitor (S8, S10).

When the time change rate DV2 reaches the reference value K and the elapsed time DELTA T1 is measured (S8: YES, S10: NO) before the total voltage reaches the end-of-charge voltage, the CPU 30 It is determined that the first secondary battery 50 and the second secondary battery 50 are unevenly charged. The CPU 30 sets a discharge time HT for discharging the first secondary battery 50 in order to equalize the SOCs of the first secondary battery 50 and the second secondary battery 50. Discharge time HT can also be called equalization control time for equalizing SOC of the 1st secondary battery 50 and the 2nd secondary battery 50. FIG.

In the memory 32 of the CPU 30, a correspondence table that associates the elapsed time ΔT1 and the discharge time HT is stored in advance. The CPU 30 functioning as the equalization control section 44 sets the discharge time HT based on the elapsed time ΔT1 and this correspondence table (S12). After setting the discharge time HT, the CPU 30 starts to discharge the first secondary battery 50 (S14). Specifically, the CPU 30 supplies the first secondary battery 50 to the first secondary battery 50. The switch Q of the corresponding discharge circuit 26 is placed in the closed state, and the elapsed time DELTA T2 after the switch Q is placed in the closed state is measured (S16). The CPU 30 discharges the first secondary battery 50 until the elapsed time ΔT2 reaches the discharge time HT (NO in S16), and the elapsed time ΔT2 is the discharge time HT. ) (S16: YES), the discharge of the 1st secondary battery 50 is complete | finished (S18), and the equalization process is complete | finished.

On the other hand, the CPU 30 functioning as the deterioration determination unit 46, when the total voltage reaches the end-of-charge voltage before the time change rate DV2 reaches the reference value K (S8: NO, S10: YES) It is determined that the deterioration of the second secondary battery 50 is in progress with respect to the first secondary battery 50, and it is determined that the battery group 12 has reached the end of life (S20). The CPU 30 notifies the user that the battery group 12 is deteriorated and that the battery group 12 needs to be replaced through a display unit such as a display and the like, and ends the equalization process.

3. Effect of this embodiment

(1) In the BMS 20 of this embodiment, the BMS 20 measures the voltage value V of the secondary battery 50 during charging, and the time change rate DV calculated from the voltage value V is The equalization of the secondary battery 50 is controlled using the elapsed time ΔT1 which is the time difference at which the reference value K is reached. According to the BMS 20, even in a flat area where it is difficult to equalize and control the secondary battery 50 based on the voltage value V, the SOC of the plurality of secondary batteries 50 during charging can be equalized and charged. have.

In particular, in the present embodiment, an olivine iron-based lithium ion secondary battery is used as the secondary battery 50 and has a flat region in which the SOC is widened in the range of 10% or more and less than 90%. On the other hand, in an olivine iron type lithium ion secondary battery, battery voltage rises rapidly with increase of SOC at the end of the charge which SOC is 90% or more. Therefore, even when attempting to equalize the plurality of secondary batteries 50 using the voltage value V of the secondary battery 50 at the end of charging, the SOC reaches up to approximately 100% due to the slight increase in the SOC. The equalization process of the secondary battery 50 cannot be completed. Therefore, it is required to equalize the plurality of secondary batteries 50 by using a flat region in which SOC exists in a range smaller than the end of charging.

In this BMS 20, the discharge of the secondary battery 50 is controlled using the time change rate DV. In addition, in the present embodiment, an olivine iron-based lithium ion secondary battery using a graphite-based material as a negative electrode is used as the secondary battery 50, and the change point at which the rate of change of time becomes larger than the reference value K in the flat region ( KS1, KS2) are present. Therefore, using these change points KS1 and KS2, the SOC of the secondary battery 50 can be estimated from the time change rate DV, and the SOC of the plurality of secondary batteries 50 is equalized using the flat region. Can be completed by one equalization process to charge the secondary battery 50.

(2) In the BMS 20 of the present embodiment, when the elapsed time ΔT1 which is the time difference between the first secondary battery 50 and the second secondary battery 50 is equal to or greater than the reference time KT, the BMS ( 20 discharges the first secondary battery 50. Generally, elapsed time (DELTA) T1 has shown the difference of SOC of these secondary batteries 50. FIG. According to this BMS 20, when the elapsed time (DELTA) T1 is more than the reference time KT, the 1st secondary battery 50 is discharged when the battery group 12 is charged by discharging the 1st secondary battery 50 ( The difference between the SOC of 50) and the second secondary battery 50 can be kept constant within a constant capacity difference corresponding to the reference time KT.

(3) In the BMS 20 of the present embodiment, the elapsed time ΔT1, that is, the time difference corresponding to the difference between the SOC of the first secondary battery 50 and the SOC of the second secondary battery 50 is used. Since the discharge time HT which equalizes the primary secondary battery 50 is set, the discharge time HT can be set with good precision, and the primary secondary battery 50 and the secondary secondary battery 50 can be set. The SOC to be charged can be equalized.

(4) In the BMS 20 of the present embodiment, the second secondary battery 50 after the elapsed time ΔT1, that is, the time change rate DV1 of the first secondary battery 50 reaches the reference value K When the time until the time change rate DV2 reaches the reference value K is greater than or equal to the reference time KT, it is determined that these secondary batteries 50 are unevenly charged. In this BMS 20, when the battery group 12 is charged by discharging the first secondary battery 50 in the above case, the secondary batteries 50 included in the battery group 12 are equalized. Can be charged.

(5) In the BMS 20 of this embodiment, before the time change rate DV2 of the second secondary battery 50 reaches the reference value K, the total voltages of the plurality of secondary batteries 50 stop charging. When charging is completed because the voltage is reached, the second secondary battery 50 is deteriorated, and it is determined that the SOC of the first secondary battery 50 and the second secondary battery 50 cannot be equalized. In this BMS 20, the battery group 12 including the secondary battery 50 which cannot be equalized by the deterioration is determined by judging that the secondary battery 50 is deteriorated in this case. It can be suppressed from being used.

(6) In the BMS 20 of the present embodiment, when detecting whether the secondary battery 50 has reached the change point during charge and discharge, the time change rate DV reaches the reference value K, Check that the voltage value V has risen to the voltage value KV2. Therefore, for example, when the second secondary battery 50 reaches the change point KS1 after the first secondary battery 50 reaches the change point KS2, the time difference therebetween is measured. The time difference at which different change points are reached may be measured to prevent the secondary battery 50 from being equalized incorrectly.

(7) In the BMS 20 of the present embodiment, since the battery group 12 is constant current charged at 0.5C charge, the battery group 12 generates a larger time change rate than the case of charging at a relatively high speed greater than 1C charge and more than 0.9C charge. can do. In the secondary battery 50, the time change rate DV caused by deterioration decreases, and it becomes difficult to detect whether the time change rate DV has reached the reference value K. As shown in FIG. In this BMS 20, since the secondary battery 50 is charged at a relatively low speed, it is easy to detect whether or not the time change rate DV has reached the reference value K even when the secondary battery 50 is deteriorated. .

<Example 2>

Embodiment 2 of this invention is demonstrated using FIG. In the present embodiment, the contents explained using the charging system 10 in the first embodiment will be described using the discharge system 10. That is, the equalization process performed in connection with the discharge control process using the discharge system 10 is demonstrated.

In this embodiment, the battery group 12 is constant current discharged. In the present embodiment, the case where the voltage value corresponding to the change point reaches the change point KS1 which is smaller among the change points KS1 and KS2 existing in the flat region is described. That is, the CPU 30 detects that the voltage value V falls to the voltage value KV1 corresponding to the change point KS1 and the time change rate DV reaches the reference value K. Also in this embodiment, the secondary battery 50 in which the time change rate DV reaches the reference value K is called the first secondary battery 50 at the earliest, and the time change rate DV is the reference value ( The secondary battery 50 which reached K) is called the 2nd secondary battery 50. FIG. That is, the first secondary battery 50 is assumed to have the lowest voltage value V (that is, the small SOC) among the plurality of secondary batteries 50, and the second secondary battery 50 has a plurality of secondary batteries 50. It is assumed that the voltage value V decreases (that is, the SOC is large) at the latest of the secondary batteries 50. In the following description, duplicate description is abbreviate | omitted about the content similar to Example 1.

1. Equalization Treatment

7 shows a flowchart of the equalization process of this embodiment executed in the CPU 30. The CPU 30 functioning as the time measuring unit 42 monitors that the time change rate DV2 of the second secondary battery 50 reaches the reference value K and at the same time the voltage value of the secondary battery 50 ( It is monitored that the total voltage which is the sum of V) decreases to reach the discharge end voltage (S8, S22). The CPU 30 functioning as the equalization control section 44 is the case where the time change rate DV2 reaches the reference value K and the elapsed time ΔT1 is measured before the total voltage reaches the discharge end voltage (S8: YES, S22: NO), the first secondary battery 50, and the second secondary battery 50 are determined to be unevenly discharged. The CPU 30 sets a discharge time HT for discharging the second secondary battery 50 in order to equalize the SOCs of the first secondary battery 50 and the second secondary battery 50 ( S12) The second secondary battery 50 is discharged over this discharge time HT (S24, S16, S26).

On the other hand, the CPU 30 functioning as the deterioration judging section 46, when the total voltage reaches the discharge end voltage before the time change rate DV2 reaches the reference value K (S8: NO, S22: YES) It is detected that the deterioration of the first secondary battery 50 is in progress with respect to the second secondary battery 50, and it is determined that the battery group 12 has reached the end of life (S28). The CPU 30 notifies the user that the battery group 12 is deteriorated through a display unit such as a display or the like and that the battery group 12 needs to be replaced, and ends the equalization process.

2. Effect of this example

(1) In the BMS 20 of this embodiment, the BMS 20 detects the time change rate DV of the secondary battery 50 during discharge, and calculates the elapsed time DELTA T1 calculated from the time change rate DV. To control the equalization of the secondary battery 50. According to this BMS 20, even in a flat area | region, SOC of the some secondary battery 50 during discharge can be equalized and discharged.

(2) In this embodiment, an olivine iron-based lithium ion secondary battery is used as the secondary battery 50, and has a flat region in which SOC is widened in the range of 10% or more and less than 90%. On the other hand, in an olivine iron-type lithium ion secondary battery, battery voltage falls rapidly with respect to the decrease of SOC at the end of discharge which SOC is less than 10%. Therefore, even when attempting to equalize the plurality of secondary batteries 50 using the voltage value V of the secondary battery 50 at the end of discharge, the SOC reaches up to approximately 0% by the slight decrease of the SOC, The equalization process of the some secondary battery 50 cannot be completed. Therefore, it is required to equalize the plurality of secondary batteries 50 by using the flat region that exists in the range where SOC is larger than the end of discharge.

In this BMS 20, the discharge of the secondary battery 50 is controlled using the time change rate DV rather than the voltage value V of the secondary battery 50. Therefore, the equalization of the SOC of the plurality of secondary batteries 50 using the flat region can be completed in one equalization process, and the secondary battery 50 can be discharged.

(3) In the BMS 20 of the present embodiment, when the elapsed time ΔT1 is equal to or greater than the reference time KT, the second secondary battery 50 is discharged to thereby discharge the first battery group 12. The difference between the SOCs of the secondary battery 50 and the secondary battery 50 can be maintained within a constant capacity difference corresponding to the reference time KT.

(4) In the BMS 20 of this embodiment, when the elapsed time ΔT1 is equal to or greater than the reference time KT, the first secondary battery 50 and the second secondary battery 50 are discharged unevenly. By judging, by discharging the second secondary battery 50, when discharging the battery group 12, these secondary batteries 50 included in the battery group 12 can be equalized and discharged.

(5) In the BMS 20 of this embodiment, before the time change rate DV2 of the second secondary battery 50 reaches the reference value K, the total voltages of the plurality of secondary batteries 50 end discharge. When the discharge is completed when the voltage is reached, the battery group 12 including the secondary battery 50 which cannot be equalized by the deterioration is determined by judging that the first secondary battery 50 is deteriorated. It can be suppressed from being used.

<Example 3>

Embodiment 3 of this invention is demonstrated using FIG. In the charging system 10 according to the present embodiment, the discharge time HT is set based on the discharge time HT stored in advance in the memory 32, and thus the discharge time HT is set during the equalization process. Different from the charging system 10. In the following description, duplicate description is abbreviate | omitted about the content similar to Example 1.

1. Equalization Treatment

8 shows a flowchart of the equalization process of this embodiment executed in the CPU 30. When the CPU 30 functioning as the time measuring unit 42 detects that the time change rate DV1 of the first secondary battery 50 reaches the reference value K (S2: YES), The measurement of time is started (S4) and the discharge of the first secondary battery 50 is started (S14). In addition, the CPU 30 includes, for all the secondary batteries 50 including the first and second secondary batteries 50, the secondary battery 50 having the time change rate DV reaching the reference value K. Is ranked and stored in the memory 32 temporarily.

Next, the CPU 30 functioning as the equalization control section 44 sets the discharge time HT of each secondary battery 50 (S32). As shown by a dotted line in FIG. 1, the memory 32 of the CPU 30 corresponds to the rank of the secondary battery 50 in which the time change rate DV reaches the reference value K, so that the discharge time HT is increased. It is memorize | stored, and it is set so that discharge time HT may become long, as the rank of the secondary battery 50 becomes high. The CPU 30 sets the discharge time HT stored in correspondence with the rank of each secondary battery 50 in the memory 32 as the discharge time HT of each secondary battery 50, The first secondary battery 50 is discharged (S34, S18) over the set discharge time HT, and the equalization process is completed.

In the charging system 10, charging is repeated for the battery group 12 a plurality of times, and the CPU 30 repeats the charging control process every time the battery group 12 is charged, and performs the equalization process. Repeat. When the equalization process is repeated, the CPU 30 repeats the equalization process using the discharge time HT stored in the memory 32.

2. Effect of this example

(1) In the BMS 20 of this embodiment, when the time change rate DV of the first secondary battery 50 reaches the reference value K during charging, the discharge of the first secondary battery 50 is started. . Therefore, the discharge of the first secondary battery 50 can be started before the time change rate DV of the other secondary battery 50 reaches the reference value K, so that the equalization at the time of charging the battery group 12 is achieved. In the process, the discharge start time of the first secondary battery 50 can be advanced.

(2) In the BMS 20 of the present embodiment, each secondary battery (from the order in which the time change rate DV reaches the reference value K during charging and the discharge time HT stored in the memory 32 in advance) Since the discharge time HT of 50) is set, the discharge time HT of each secondary battery 50 can be easily set early.

<Example 4>

Example 4 of this invention is demonstrated using FIG. In the present embodiment, the contents described using the charging system 10 in the third embodiment will be described using the discharge system 10. That is, the equalization process performed in connection with the discharge control process using the discharge system 10 is demonstrated.

In this embodiment, the case where the change point KS1 is reached will be described. Also in the present embodiment, the secondary battery 50 at which the voltage change rate DV reaches the reference value K is called the first secondary battery 50 at the earliest, and the voltage change rate DV is the reference value ( The secondary battery 50 which reached K) is called the 2nd secondary battery 50. FIG. In the following description, duplicate description is abbreviate | omitted about the content similar to Example 1 and Example 3.

1. Equalization Treatment

9 shows a flowchart of the equalization process of this embodiment executed in the CPU 30. When the CPU 30 functioning as the time measuring unit 42 detects that the time change rate DV1 of the second secondary battery 50 has reached the reference value K (S42: YES), The measurement of time is started (S4) and the discharge of the second secondary battery 50 is started (S24). Next, the CPU 30 functioning as the equalization control unit 44 stores the discharge time HT stored in correspondence with the rank of each secondary battery 50 in the memory 32, for each secondary battery 50. Is set as the discharge time HT (S32), the second secondary battery 50 is discharged over the set discharge time HT (S34, S26), and the equalization process is completed. The discharge time HT is stored in the memory 32 of the CPU 30 in correspondence with the rank of the secondary battery 50 in which the time change rate DV reaches the reference value K, and the secondary battery 50 is stored. Is lowered, the discharge time HT is set to be longer.

2. Effect of this example

In the BMS 20 of this embodiment, it is possible to advance the discharge start time of each secondary battery 50 during discharge, and in the equalization process at the time of discharging the battery group 12, the second secondary battery 50 The discharge start time of can be advanced.

<Other Embodiments>

This invention is not limited to the Example demonstrated by the said description and drawing, For example, the following various aspects are also included in the technical scope of this invention.

(1) In the above embodiment, the charging system (discharge system) 10 has one BMS 20, and functions BMS, the equalization control section 44, the deterioration determination section 46, and the like. Although shown using the example performed by one CPU 30 which 20 has, this invention is not limited to this. For example, each part may be comprised by mutually different CPU, BMS, etc., and each part may be comprised using independent apparatus etc ..

(2) In the above embodiment, description was made using an example in which an olivine iron-based battery using a graphite-based material as a negative electrode was used as the secondary battery 50, but the present invention is not limited thereto. For example, it can be used also in the other battery which used the graphite type material for the negative electrode, and can be used also in the battery which does not have a flat area | region. In this case, the reference value K is appropriately set according to the charge and discharge characteristics of each battery.

(3) In the above embodiment, the secondary battery 50 has been described using an example of constant current charging (constant current discharge), but the charging method (discharge method) of the secondary battery 50 is not limited to this. For example, the secondary battery 50 may be constant voltage charged (constant voltage discharge) or constant power charged (constant power discharge).

(4) In the above embodiment, an example in which the charging system (discharge system) 10 is mounted on the electric vehicle and the equalization processing is performed on the battery group 12 has been described. It is not limited to this embodiment.

(5) In the above embodiment, when the elapsed time ΔT is measured, the time change rate DV of the voltage value V of any of the secondary batteries 50 reaches the reference value K. Although measurement is started, you may measure time from the start of a charge control process (discharge control process). That is, the CPU 30 functioning as the time measuring unit 42 measures the time from the start of the charge control process (discharge control process), and the time change rate DV of the voltage value V of each secondary battery 50. ) May be measured until the reference value K is reached, and the elapsed time DELTA T may be measured as a difference between the arrival times.

(6) In Example 1 described above, an example of initiating the discharge of the first secondary battery 50 after setting the discharge time HT has been described. For example, as shown in FIG. The discharge may be started before the time HT is set, and the discharge time HT may be set after the start of the discharge.

10 shows a flowchart of an equalization process of another embodiment.

When the CPU 30 detects that the time change rate DV1 of the first secondary battery 50 reaches the reference value K (S2: YES), the CPU 30 starts to measure the time since the arrival (S4: S4). At the same time, discharge of the first secondary battery 50 is started (S14).

Next, the CPU 30 monitors that the time change rate DV2 of the second secondary battery 50 reaches the reference value K, and at the same time, is the sum of the voltage values V of the secondary battery 50. It is monitored that the total voltage increases to reach the charging end voltage (S8, S10). When the time change rate DV2 reaches the reference value K and the elapsed time DELTA T1 is measured (S8: YES, S10: NO) before the total voltage reaches the end-of-charge voltage, the CPU 30 1 The discharge time HT for discharging the secondary battery 50 is set (S 12). Then, the first secondary battery 50 is discharged (S16, S18) over the set discharge time HT, and the equalization process is completed.

On the other hand, when the total voltage reaches the end of charge voltage (S8: NO, S10: YES) before the time change rate DV2 reaches the reference value K, the CPU 30 receives the first secondary battery 50. Stopping the discharge of the battery (S42) and at the same time detect the deterioration of the second secondary battery 50 as compared to the first secondary battery 50, the battery group 12 has reached the end of life Determine (S 20). The CPU 30 notifies the user that the battery group 12 is deteriorated through a display unit such as a display or the like and that the battery group 12 needs to be replaced, and ends the equalization process.

(7) In Examples 1 and 2, an example in which the life judgment of the battery group 12 is executed when the total voltage of the plurality of secondary batteries 50 reaches the end of charge voltage (discharge end voltage) is used. Although it demonstrated, the termination voltage is set to each secondary battery 50, and when any one of the secondary batteries 50 reaches | attains the termination voltage, you may perform determination of the life of the battery group 12. FIG. That is, after the time change rate DV1 of the first secondary battery 50 reaches the reference value K, and before the time change rate DV2 of the second secondary battery 50 reaches the reference value K, When the voltage value V of the primary secondary battery 50 reaches the charge upper limit voltage (discharge end voltage), the life of the battery group 12 may be judged.

(8) In the first and second embodiments, the elapsed time ΔT is measured, and an explanation will be made using an example of setting the discharge time HT from the elapsed time ΔT and the correspondence table stored in the memory 32. However, the present invention is not limited thereto. For example, the charge-discharge current ZI to the battery group 12 is measured, and the capacitance difference ΔY is calculated by multiplying the elapsed time ΔT by the charge-discharge current ZI, and the capacitance difference ΔY. ) May be divided by the equalization control current HI flowing by switching the switch Q of the discharge circuit 26 to the closed state to obtain the discharge time HT. Further, only the discharge time HT determined by the predetermined elapsed time ΔT may be discharged.

Discharge time (HT) = capacity difference (ΔY) / equalization control current (HI)

10: charge system (discharge system), 12: battery group, 20: BMS, 22: ammeter, 24: voltmeter, 26: discharge circuit, 30: CPU, 42: time measurement unit, 44: equalization control unit, 46: deterioration determination unit , 50: secondary battery, DV: rate of change of time, HT: discharge time, KT: reference time, K: reference value, ΔT: elapsed time

Claims (19)

A state management apparatus for managing a state of a plurality of power storage elements connected in series,
A voltage measuring unit measuring voltage of each power storage element individually;
A time measuring unit for measuring a time difference from when the time change rate of the voltage of one power storage element reaches a reference value, and then until the time change rate of the voltage of another power storage element reaches a reference value;
A discharge unit for discharging the respective power storage elements individually; And
An equalization control unit controlling the discharge unit using the time difference
State management device comprising a. The method of claim 1,
The plurality of power storage elements include a first power storage element and a second power storage element,
The equalization control unit acquires a first time difference between when the time change rate of the first power storage element reaches a reference value and the time change rate of the second power storage element reaches a reference value, and has a reference time. The first power storage element when the power storage element of the battery is being charged and the first time difference is greater than or equal to the reference time, and the first power storage element is discharged using the first time difference, and the first time difference is less than the reference time. And a state management device which does not discharge said second power storage element. The method of claim 2,
Further comprising a deterioration determination unit for determining the deterioration of the power storage element,
The deterioration determination unit, the plurality of power storage elements are being charged, and before the time change rate of the voltage of the second power storage element reaches the reference value, the charging of the plurality of power storage elements is completed and the charging of the second power storage element is terminated. In one case, the state management device determines that the second power storage element is deteriorated. The method of claim 2,
Further comprising a deterioration determination unit for determining the deterioration of the power storage element,
The deterioration determination unit is an elapsed time after the plurality of power storage elements are being charged and the time change rate of the voltage of the first power storage element reaches the reference value before the time change rate of the voltage of the second power storage element reaches the reference value. And when it reaches this prescribed time, it is judged that the said 2nd electrical storage element has deteriorated. The method of claim 1,
The plurality of power storage elements include a first power storage element and a second power storage element,
The equalization control unit acquires a first time difference between when the time change rate of the first power storage element reaches a reference value and the time change rate of the second power storage element reaches a reference value, and has a reference time. The first power storage element when the power storage element is being discharged and the first time difference is greater than or equal to the reference time, and the second power storage element is discharged using the first time difference, and the first time difference is less than the reference time. And a state management device which does not discharge said second power storage element. The method of claim 5,
Further comprising a deterioration determination unit for determining the deterioration of the power storage element,
The deterioration determination unit is configured to discharge the plurality of power storage elements before the time change rate of the voltage of the second power storage element reaches the reference value when the plurality of power storage elements are being discharged, and thus the discharge of the second power storage element is terminated. In one case, the state management device determines that the first power storage element is deteriorated. The method of claim 5,
Further comprising a deterioration determination unit for determining the deterioration of the power storage element,
The deterioration determination unit is an elapsed time after the plurality of power storage elements are being discharged and the time change rate of the voltage of the first power storage element reaches the reference value before the time change rate of the voltage of the second power storage element reaches the reference value. The state management apparatus which judges that the said 1st power storage element has degraded when this prescribed time is reached. 8. The method according to any one of claims 2 to 7,
And the equalization control unit sets a discharge time for discharging the first power storage element or the second power storage element using the first time difference. The method according to any one of claims 1 to 8,
The time measuring unit determines that the time change rate of the voltage of the power storage element has reached the reference value when the voltage of the power storage element reaches the reference voltage and the rate of change of the voltage of the power storage element reaches the reference value. , State management device. 10. The method according to any one of claims 1 to 9,
And the power storage element is constant current charged or constant current discharged. The method of claim 10,
A state management device in which the charge / discharge rate of the power storage element is set to 1C or less. The method of claim 11,
The state management apparatus in which the charge / discharge rate of the power storage element is set to less than 0.9C. 13. The method according to any one of claims 1 to 12,
And a cathode of said power storage element is formed of a graphite-based material. The method according to any one of claims 1 to 13,
The power storage device is an olivine iron-based lithium ion secondary battery, the state management device. A state management apparatus for managing a state of a plurality of power storage elements connected in series,
A voltage measuring unit measuring voltage of each power storage element individually;
A discharge unit for discharging the respective power storage elements individually;
A storage unit in which discharge time is stored in correspondence with the order in which the time change rate of the voltage of each power storage element reaches a reference value; And
Equalization control unit for controlling the discharge unit
Including,
And the equalization control unit discharges the power storage element over the discharge time stored in correspondence with the order in which the time change rate of the voltage of each power storage element reaches the reference value. A state management apparatus for managing a state of a plurality of power storage elements connected in series,
A voltage measuring unit measuring voltage of each power storage element individually;
A discharge unit for discharging the respective power storage elements individually; And
Equalization control unit for controlling the discharge unit
Including,
And the equalization control unit starts discharging the power storage element when the rate of change of the voltage of each power storage element reaches a reference value. As a method of equalizing a power storage element for equalizing the states of a plurality of power storage elements connected in series,
A voltage measuring step of separately measuring the voltage of each power storage element during charge and discharge;
A time measurement step of measuring a time difference from when the time change rate of the voltage of one power storage element reaches a reference value, and then until the time change rate of the voltage of another power storage element reaches a reference value; And
A discharging step of individually discharging the respective power storage elements by using the time difference
Equalization method of the power storage device comprising a. As a method of equalizing a power storage element for equalizing the states of a plurality of power storage elements connected in series,
A voltage measuring step of separately measuring the voltage of each power storage element during charge and discharge;
A discharging step of discharging the respective power storage elements individually
Including,
In the discharging step, the power storage element is equalized by discharging the power storage element over a preset discharge time in correspondence with the order in which the time change rate of the voltage of each power storage element reaches the reference value. As a method of equalizing a power storage element for equalizing the states of a plurality of power storage elements connected in series,
A voltage measuring step of separately measuring the voltage of each power storage element during charge and discharge;
A discharging step of discharging the respective power storage elements individually
Including,
In the discharging step, when the time change rate of the voltage of each power storage element reaches the reference value, discharge of the power storage element is initiated.

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