JP2007166789A - Method of determining fully charged capacity of secondary battery and determining device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of estimating a deterioration state of a secondary battery and a determining device capable of realizing the method. <P>SOLUTION: This method is a method for estimating the deterioration state of the secondary battery. This method is provided with a process of continuously measuring the voltage of the secondary battery while charging the secondary battery with a constant current; a process of storing the continuously measured voltage in association with a charging time; a process of calculating a voltage change ratio indicating the relation between a change of the voltage in time of the secondary battery which has been stored before the voltage of the secondary battery reaches a predetermined voltage and the charging time, from the data, when the continuously measured voltage of the secondary battery reaches the predetermined voltage; and a process of estimating the fully charged capacity of the second battery from the calculated voltage change ratio. In this case, the predetermined voltage is set at a voltage level in which the polarization voltage of the second battery is saturated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for estimating a full charge capacity of a secondary battery. The present invention also relates to an apparatus for discriminating between a secondary battery with a sufficient full charge capacity and a secondary battery with an insufficient full charge capacity based on the estimated full charge capacity.

In the secondary battery, the full charge capacity is reduced by repeating the charge / discharge cycle. When an overdischarge phenomenon or an overcharge phenomenon occurs, a decrease in the full charge capacity is promoted. On the other hand, it is difficult to directly measure the full charge capacity of a secondary battery currently used, for example, a secondary battery mounted on an electric vehicle or a hybrid vehicle.
Therefore, a technique for estimating the full charge capacity of the secondary battery being used is required.

  In order to estimate the full charge capacity of a secondary battery mounted on an automobile, the technique of Patent Document 1 has been developed. With the technology of Patent Document 1, the capacity of a secondary battery in an unused state (not deteriorated) can be charged and discharged, and the secondary battery that has started use (a state in which deterioration has progressed) can be charged and discharged. The degree of deterioration of the secondary battery is calculated from the capacity, and the full charge capacity of the secondary battery is estimated from the degree of deterioration.

JP 2004-354050 A

The inventors' research has shown that the full charge capacity estimated by the prior art has a poor correlation with the actual full charge capacity.
The cause is presumed as follows. The progress of charging and the change in battery voltage are not necessarily linear. In general, the battery voltage increases rapidly at the initial stage of charging, but gradually changes thereafter. In order to estimate the full charge capacity, it is necessary to distinguish and estimate what state the secondary battery being charged is in. However, the conventional technology does not consider what state the secondary battery being charged is in. In order to estimate the full charge capacity without distinguishing between the measurement result during the period when the battery voltage rises rapidly and the measurement result during the period when the battery voltage rises stably at a constant speed, the reliability of the estimation result Is estimated to be low.

The inventors have found that the above problem can be overcome by the following very simple method.
(1) Do not rely on measurement results during a period when the battery voltage rises rapidly. The full charge capacity is estimated based only on the measurement result during the period when the battery voltage rises stably at a constant speed. In order to adopt the measurement value in the latter period, the battery voltage of the secondary battery being charged is continuously measured and memorized, while when the predetermined voltage is reached, it is measured within the previous previous period. The full charge capacity is estimated from the stored measurement value. According to this, the full charge capacity can be estimated based only on the measurement result in the period in which the battery voltage rises stably at a constant speed.
(2) The full charge capacity is estimated from the voltage change rate with respect to time of the secondary battery charged with a constant current.
When the voltage change rate of (2) is calculated during the period in which the battery voltage is known to be stably rising at a constant speed according to (1), the voltage change rate becomes the actual full charge capacity. A good correlation was confirmed. In the present invention, the above knowledge is utilized.

The full charge capacity estimation method of the present invention includes a step of continuously measuring the voltage of the secondary battery while charging the secondary battery at a constant current, and storing the voltage continuously measured in association with the charging time. The voltage change rate with respect to the charging time is obtained from the data indicating the time change of the voltage of the secondary battery previously stored when the voltage of the secondary battery measured continuously reaches the predetermined voltage. And a step of estimating the full charge capacity of the secondary battery from the calculated voltage change rate. Here, the predetermined voltage is set to a voltage level at which a polarization voltage of the secondary battery is saturated.
Here, the case where the voltage of the secondary battery is continuously measured includes not only the case where the voltage is continuously measured by an analog circuit, but also the case where the voltage is intermittently measured by a digital circuit at fine sampling intervals. If measurement is performed at a sampling interval sufficiently fine with respect to the charging time, it can be evaluated that measurement is continuous in a practical sense.

In this method, since charging is performed at a constant current, the charging time and the charging capacity are proportional. The voltage change rate with respect to time and the voltage change rate with respect to the charge capacity are proportional and can be converted.
Polarization occurs in an actual secondary battery. In the initial stage of charging, a part of the charging current is consumed for the generation of polarization. The battery voltage changes rapidly due to the influence of polarization. The change in battery voltage at this stage is not proportional to the charge capacity. If the full charge capacity is estimated using the measured value during this period, the error is large. When charging is continued, the polarization generated in the secondary battery is saturated, and the influence of the polarization does not affect the rate of change of the battery voltage.
In the second half of charging, the battery voltage rises stably at a constant speed. Therefore, if the voltage that reaches the second half of charging is set as a predetermined voltage, it can be seen that it is a period in which the battery voltage rises stably at a constant speed in the immediately preceding period.
According to the studies by the present inventors, it is found that the voltage change rate obtained when the secondary battery is charged at a constant current during the period when the battery voltage stably rises at a constant speed correlates well with the full charge capacity. I came. It has been found that the full charge capacity is small when the voltage change rate is large, and the full charge capacity is large when the voltage change rate is small.
In this method, a simple process of charging with a constant current is performed, and the full charge capacity is accurately estimated by paying attention to the voltage change rate in the period immediately before the predetermined voltage is reached.

  The present invention can also be embodied in an apparatus that discriminates between a secondary battery having a sufficient full charge capacity and a secondary battery having an insufficient full charge capacity from the estimated full charge capacity. This device stores charging means for charging a secondary battery at a constant current, means for continuously measuring the voltage of the secondary battery being charged, and the continuously measured voltage in association with the charging time. The voltage change rate with respect to the charging time is calculated from the data indicating the time change of the voltage of the secondary battery previously stored when the voltage of the secondary battery reaches a predetermined voltage. And a means for comparing the calculated voltage change rate with a threshold value. Here, the predetermined voltage is set to a voltage level at which the polarization voltage of the secondary battery is saturated.

  According to the above apparatus, since the voltage change rate that correlates well with the full charge capacity is used, it is possible to accurately distinguish between a secondary battery with a sufficient full charge capacity and a secondary battery with an insufficient full charge capacity.

The main forms of the embodiments described in detail below are listed first.
(Embodiment 1) The secondary battery is a vehicle-mounted secondary battery.
(Mode 2) The secondary battery is a secondary battery that drives an electric motor of a hybrid vehicle.
(Mode 3) The secondary battery is a nickel metal hydride battery.
(Mode 4) The secondary battery is charged with a low current. When the secondary battery is charged with a large current, the battery voltage rises to the battery voltage at the later stage of charging before the polarization voltage is saturated. When charging at a low current, the polarization voltage saturates before the battery voltage rises to the battery voltage at the later stage of charging. When charged at a relatively low current, the full charge capacity can be estimated with high accuracy.
(Embodiment 5) The determination device includes a temperature sensor that measures the temperature of the secondary battery, and a unit that corrects a threshold value to be compared with the voltage change rate based on the detection result of the temperature sensor.
(Mode 6) The discriminating apparatus waits for a predetermined time to elapse after the start of operation of the discriminating apparatus and starts charging. The time is adjusted to a time when the activation polarization of the electrode is eliminated.

<Example 1>
FIG. 1 shows a secondary battery 30 mounted on the hybrid vehicle 1 and an apparatus 10 for determining whether the secondary battery 30 has been fully charged or has deteriorated until it becomes insufficient. The hybrid vehicle 1 includes an engine 2 and a motor 3 that is a second drive source. The motor 3 is a generator motor that operates as an electric motor that generates driving force using the electric power of the secondary battery 30 and also operates as a charger that generates electric power using the rotational force and charges the secondary battery 30. is there. The output of the engine 2 and the output of the motor 3 are transmitted to the wheels 6 through the power distributor 4 and the drive shaft 5.
The motor 3 is connected to the secondary battery 30 via the inverter 7 and the wiring switching means 32. The motor 3 is also connected to the determination device 10 via the wiring switching means 32. The discriminating apparatus 10 includes a low current power supply 16.
In a state where the hybrid vehicle 1 is used, the wiring switching unit 32 connects the motor 3 and the secondary battery 30. In a state where the hybrid vehicle 1 is not used, the wiring switching unit 32 connects the motor 3 and the determination device 10. In a state where the motor 3 and the determination device 10 are connected, the secondary battery 30 is charged using the low current power source 16 to determine whether the full charge capacity is sufficient or has deteriorated until it becomes insufficient.
Note that the low current power supply 16 only needs to be connectable to a control unit 20 (see FIG. 2) of the determination device 10 described in detail later, and does not need to be built in the determination device 10. Moreover, the structure which removes the secondary battery 30 from the hybrid vehicle 1, and connects the removed secondary battery 30 with the determination apparatus 10 may be sufficient.

The determination device 10 charges the secondary battery 30, estimates the full charge capacity of the secondary battery 30, and determines whether the estimated full charge capacity is sufficient or has deteriorated until it becomes insufficient.
The configuration of the discrimination device 10 is shown in FIG. The discrimination device 10 includes a voltage sensor 14 that measures a voltage between terminals of the secondary battery 30, a temperature sensor 12 that measures the temperature of the secondary battery 30, a constant current power supply 16 that charges the secondary battery 30, and a control. The unit 20 is configured.

The control unit 20 is composed of a microprocessor centered on the CPU 22. In addition to the CPU 22, the control unit 20 includes a ROM 24 that stores a control program, a RAM 26 that temporarily stores measurement data of the voltage sensor 13 and the temperature sensor 12, and a timer 28.
The control unit 20 controls the constant current power supply 16 according to the control program stored in the ROM 24, and charges the secondary battery 30 in a state where the charging current is kept constant. The control unit 20 measures the battery voltage being charged by the voltage sensor 14, samples the battery voltage continuously measured by the voltage sensor 14 at fine time intervals, and stores the sampled voltage in the RAM 26. Similarly, the control unit 20 measures the battery temperature during charging by the temperature sensor 12, samples the battery temperature continuously measured by the temperature sensor 12 at fine time intervals, and stores the sampled temperature in the RAM 26. The RAM 26 stores the battery voltage and the battery temperature in a state associated with the elapsed time from the start of charging. The RAM 26 stores data indicating changes over time in the battery voltage and battery temperature, and stores data that can be used to calculate the change width (voltage change rate) of the battery voltage per unit time by subsequent analysis. is doing. The control unit 20 calculates the change width (voltage change rate) of the battery voltage from the battery voltage and battery temperature stored in the RAM 26 with time, compares the calculated voltage change rate with a threshold value, and compares the comparison result. Output to a display device (not shown).

FIG. 3 is a flowchart showing the processing contents executed by the determination device 10. The determination procedure will be described with reference to FIG.
When the engine 2 and the motor 3 of the hybrid vehicle 1 are stopped, the wiring switching unit 32 is switched, and the secondary battery 30 is connected to the determination device 10. Next, the space between the positive terminal and the negative terminal of the secondary battery 30 is opened for a predetermined time, and charging and discharging are maintained (S1). If the secondary battery 30 is maintained for a certain period of time without being charged or discharged, the activated polarization of the electrode disappears. In Step 1, the secondary battery 30 is maintained in a state in which neither charging nor discharging is performed for a time (1 hour) when the activation polarization of the electrode disappears. Instead, the open circuit voltage is measured while maintaining the secondary battery 30 in a state in which neither the charging nor discharging is performed, the voltage change rate with respect to time of the open circuit voltage is obtained, and until the change rate becomes a certain value or less. The time may be a predetermined time. When the activation polarization of the electrode disappears, the voltage change rate of the open circuit voltage decreases to near zero.

After the opening process of the secondary battery 30 has elapsed for a predetermined time, the CPU 22 controls the constant current power supply 16 and starts the charging process for the secondary battery 30. Here, charging is performed with the charging current kept constant. During charging, the CPU 22 samples the battery voltage continuously measured by the voltage sensor 14 at fine time intervals and stores it in the RAM 26. Similarly, the battery temperature continuously measured by the temperature sensor 12 is sampled at fine time intervals and stored in the RAM 26 (S2). The charging current is adjusted to a low current. For example, in the case of the secondary battery 30 having an initial full charge capacity of 6.5 Ah (initial state that is not deteriorated), the battery is charged with a constant current of 1 A or less that requires 6 hours or more to complete charging. When charging is performed at a low current, the polarization voltage is saturated at the initial stage of charging, and the subsequent polarization electrode is maintained constant. When charged with a low current, the polarization electrode can be kept constant during the latter half of the charging. In the second half of charging, a relationship in which the battery voltage increases in proportion to the charging capacity can be obtained.
The charging process of the secondary battery 30 is performed until a predetermined voltage is reached (S3). The predetermined voltage may be set to a voltage value between the upper limit of the SOC (state of charge) range in which the secondary battery is normally used and the SOC at which the overcharge phenomenon starts. For example, in the case of a nickel metal hydride battery, the SOC range during normal use is 40 to 80%. In the case of a nickel metal hydride battery, the SOC at which an overcharge phenomenon of gas generation occurs is 95% or more. Therefore, in the case of a nickel metal hydride battery, the predetermined voltage may be set to a voltage value between 80% and 95% SOC.
The predetermined voltage when the charging is stopped may be equal to the SOC that stops the charging of the secondary battery 30 during normal use. For example, if the secondary battery is used in the range of 40 to 80% SOC (for example, the nickel-metal hydride battery for hybrid vehicles is used in the range of 40 to 80%. 6-cell nickel connected in series The hydrogen battery has a battery voltage of 8.371 V when the SOC is 80% and stops charging when charged to that voltage.) The battery voltage when the SOC is 80% is set to a predetermined voltage.
Assuming that the battery voltage when the SOC is 80% is a predetermined voltage, the polarization electrode is already saturated and kept constant in the period immediately before that, and the battery voltage increases in proportion to the charge capacity. ing. Since the battery voltage when the SOC is 80% is a predetermined voltage, the charging current is a small current, and an open period is provided prior to the start of charging, immediately before the battery voltage increases when the SOC is 80%. In this period, the polarization electrode is already saturated and kept constant, and it is guaranteed that the battery voltage increases in proportion to the charge capacity.

If the answer is yes in step S3, the voltage change rate with respect to the charging time is calculated based on the data indicating the voltage change in the immediately preceding period stored in the RAM 26. The voltage change rate is a voltage change width per unit time, and as shown in FIG. 6, the unit time T is set shorter than the period in which the battery voltage increases in proportion to the charge capacity. The voltage change rate calculated in step S4 corresponds to a proportional count of the battery voltage with respect to the charge capacity. It has been found that the smaller the value is, the larger the full charge capacity is, and the larger the value is, the smaller the full charge capacity is.
In step S5 of FIG. 3, the calculated voltage change rate is compared with a threshold value. Here, a value that can be determined that the full charge capacity is insufficient if the threshold is less than the threshold and that the full charge capacity is not insufficient if the threshold is equal to or greater than the threshold is used. In this embodiment, a threshold indicated by L1 in FIG. 7 is used. Although L1 in FIG. 7 is shown as a voltage change rate with respect to the charge capacity, the charge capacity and the charge time are proportional to each other because of constant current charge, and can be converted into a voltage change rate with respect to the charge time.

If it is less than the threshold value, the full charge capacity is insufficient, and if it is greater than or equal to the threshold value, the threshold value for determining that the full charge capacity is not insufficient varies slightly depending on the battery temperature. If the battery temperature is high, the voltage change rate increases even with the same full charge capacity. It is correct to use a large threshold when the battery temperature is high. If the battery temperature is low, the voltage change rate decreases even with the same full charge capacity. If the battery temperature is low, it is correct to use a small threshold. In this embodiment, the reference threshold value is corrected by the battery temperature to be a threshold value. If the battery temperature is high, use a greatly modified threshold. When the battery temperature is low, a small corrected threshold value is used.
If the voltage change rate is equal to or greater than the threshold, it is determined that the battery is a deteriorated battery with insufficient full charge capacity. (S5).

FIG. 4 is a graph showing a change in voltage with respect to charge capacity when constant current charging (1 A) is performed using six nickel-metal hydride batteries in an unused state (hereinafter referred to as “unused batteries”) connected in series. It is. FIG. 4 shows the results of nickel-metal hydride batteries having SOCs of 40%, 50%, 60%, 70%, and 80% at the start of charging.
As is clear from the graph of FIG. 4, polarization occurs in the charging start period and the battery voltage rapidly increases. In the latter charging period, the battery voltage linearly changes with respect to the charging time. When the polarization voltage is saturated and maintained at a constant value, the rate of change of the voltage with respect to the charge capacity becomes equal even if the charge start SOC is different.

  The trend of voltage change will be described in detail with reference to FIG. FIG. 5 is a graph showing a change in battery voltage (V) when a nickel hydride battery is charged with a constant current at 1A. In the graph of FIG. 5, the vertical axis indicates the battery voltage (V), and the horizontal axis indicates the SOC. The SOC at the start of charging of the secondary battery is 40%. The battery voltage (V) of the secondary battery includes the electromotive voltage (Vsoc) depending on the SOC of the secondary battery, the product (IR) of the charging current (I) and the internal resistance (R) of the secondary battery, and the secondary battery. It is the sum of polarization voltage (Vp) related to polarization in the battery. In the case of a nickel metal hydride battery, the internal resistance value (R) when the SOC is 40 to 80% is substantially constant. If the charging current (I) is a constant current, the (IR) at an SOC of 40 to 80% is substantially constant.

In the graph of FIG. 5, the part indicated by A indicates the battery voltage at the start of charging. At this time, since charging current for polarization is not consumed at the start of charging, the influence of the polarization voltage Vp does not occur. Therefore, the battery voltage V is the sum of Vsoc and IR.
In the graph of FIG. 5, a portion indicated by B indicates a voltage change at the initial stage of charging. In the initial stage of charging, the polarization voltage (Vp) gradually increases. For this reason, the battery voltage V increases in a curve at the initial stage of charging.
A portion indicated by C in the graph of FIG. 5 indicates a voltage change during a period in which the polarization voltage Vp is saturated. When the polarization voltage Vp related to the initial charging is saturated, the battery voltage (V) with respect to the SOC is determined according to the electromotive voltage (Vsoc) depending on the SOC of the secondary battery. If the polarization voltage (Vp) is saturated, the change in the battery voltage V with respect to the SOC follows the same trajectory even when the SOC at the start of charging is different. Therefore, the voltage change rate calculated in the region C where the change of the polarization voltage (Vp) is saturated shows a substantially constant value. However, the voltage change rate differs for each battery.
Based on the voltage change rate, the full charge capacity of the secondary battery and the deterioration state of the secondary battery can be estimated and displayed (S5). At this time, the full charge capacity is corrected based on the battery temperature measured by the temperature sensor.

A battery in which deterioration has progressed compared to an unused battery has less full charge capacity than an unused battery. Therefore, a battery with a reduced full charge capacity indicates that it has deteriorated. A secondary battery having a larger voltage change rate has a reduced full charge capacity, indicating that the deterioration state is progressing. Such an event will be described with reference to FIG. FIG. 6 shows changes in battery voltage (V) when a nickel-metal hydride battery (unused battery) in an unused state and a nickel-metal hydride battery in a deteriorated state (hereinafter referred to as “deteriorated battery”) are charged at a constant current of 1 A. It is a graph to show. The SOC at the start of charging of the deteriorated battery and the unused battery was 40%, and the SOC at the end of charging was 80%. Therefore, the battery voltage at the end of charging is 8.317 V corresponding to a battery voltage value with an SOC of 80%. The temperature is 25 ° C.
In the graph of FIG. 6, the vertical axis indicates the battery voltage (V), and the horizontal axis indicates the charge capacity (Ah). In the graph of FIG. 6, the result of the deteriorated battery is indicated by a solid line, and the result of the unused battery is indicated by a broken line. T indicates a period immediately before the SOC reaches 80%. T is a period during which the battery voltages of the deteriorated battery and the unused battery stably rise at a constant speed.
α1 indicates an inclination angle of the period T in which the voltage change of the deteriorated battery changes linearly. ΔV1 indicates a voltage change rate during a period when the deteriorated battery is T.
α0 indicates the angle of inclination of the period T in which the voltage change of the unused battery changes linearly. ΔV0 indicates the voltage change rate that the unused battery has increased in the period T.

In the latter stage of charging when the polarization voltage is saturated, the battery voltage changes linearly with respect to the charging time. In the period T, the inclination angle of the voltage change is larger for the deteriorated battery inclination α ₁ than for the unused battery inclination α ₀ . From this, it can be estimated that the secondary battery having a larger slope of the battery voltage with respect to the charging time in the latter charging stage is more deteriorated.
Further, the voltage change rate can be calculated from the voltage change increased in a predetermined period (here, period T) in the latter half of charging. Comparing the voltage change rates of the deteriorated battery and the unused battery, the voltage change rate V _{1 of the} deteriorated battery is larger than the voltage change rate V ₀ of the unused battery. From this, it can be estimated that the secondary battery having a higher voltage change rate in the later stage of charging is more deteriorated.

<Test>
Based on the voltage change rate calculated by the procedure of the above example, a test for comparing the state of the unused battery and the deteriorated battery was performed. The internal resistance of the deteriorated battery used in this test was prepared to be equivalent to the internal resistance of the unused battery. This test was performed by setting the SOC of each sample battery before the test to 60%. This test was conducted in a constant temperature atmosphere at 25 ° C.
This test was conducted according to the following procedure.
First, each sample battery was left open for 1 hour. Next, the charging voltage of the sample battery reaches 8.371V (the battery voltage when the SOC is 80% when the 6-series-connected nickel-metal hydride batteries are constant-current charged at 1A), and the constant-current charging of 1A is performed. went. The test result of each sample battery is shown in the graph of FIG. The horizontal axis of FIG. 7 shows the voltage change rate calculated by the above method, and the vertical axis shows the full charge capacity calculated by other measuring means. In FIG. 7, those indicated by white display are unused batteries, and those indicated by solid display are degraded batteries.

As shown in FIG. 7, the unused full-charge capacity of the battery is greater than C _1, the full charge capacity of the deteriorated battery is in the range of C ₁ -C _2. As a result of the test, it was confirmed that the unused battery had a low voltage change rate, and the deteriorated battery had a large voltage change rate. Second time to set the predetermined threshold value of the voltage change rate, the state of the secondary battery when the voltage change rate is smaller than L ₁ "good", the voltage change rate in the range of L ₁ ~L ₂ state "capacity reduction" in the next cell, the voltage change rate may be determined separately as such "essential exchange" when greater than L _2.
It can be seen that by using such a method, the full charge capacity and the deterioration state of the secondary battery can be clearly estimated.

  The embodiment described above can be variously changed, modified, modified, and / or improved. Various changes can be made without departing from the spirit and scope of the invention. Accordingly, the apparatus and method according to the present invention are intended to include all known or later developed changes, modifications, variations and / or improvements.

For example, although the said Example described the method of detecting the deterioration state of the secondary battery mounted in the hybrid vehicle, it is not restricted to this. For example, the present invention may be applied to a secondary battery for an electric vehicle or a secondary battery for an auxiliary battery.
Further, the present invention is not limited to a secondary battery mounted on a vehicle, and may be applied to a small secondary battery used for a power source of a portable device.
Of course, the type of secondary battery is not limited. In the said Example, although the nickel hydride battery was illustrated mainly, a lithium ion battery, a nickel cadmium battery, and a lead acid battery may be sufficient.

  The technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

It is a schematic diagram which shows the structure of a hybrid vehicle It is a schematic diagram which shows the structure of a state estimation apparatus. It is a flowchart which shows the state estimation method concerning an Example. It is a graph which shows the relationship of the voltage with respect to the charge time when carrying out constant current charge of the nickel hydride battery of SOC. It is a graph which shows the change of battery voltage (V) when a nickel hydride battery with 40% of SOC is charged with constant current. It is a graph which shows the change of charging voltage (V) when an unused battery and a deterioration battery are charged with constant current at 1A. It is a graph which shows the relationship between a full charge capacity | capacitance and a voltage change rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hybrid vehicle 2 Engine 3 Motor / generator 4 Power distribution mechanism 5 Wheel shaft 6 Wheel 7 Inverter 10 State estimation apparatus 12 Temperature sensor 14 Voltage sensor 16 Constant current power supply 20 Control unit 22 CPU
24 ROM
26 RAM
28 Timer

Claims (2)

It is a method for estimating the full charge capacity of a secondary battery,
A step of continuously measuring the voltage of the secondary battery while charging the secondary battery at a constant current;
Storing the continuously measured voltage in association with the charging time;
A step of calculating a voltage change rate with respect to a charging time from data indicating a temporal change in the voltage of the secondary battery stored in advance when the voltage of the continuously measured secondary battery reaches a predetermined voltage. When,
A step of estimating a full charge capacity of the secondary battery from the calculated voltage change rate,
The method for estimating a full charge capacity of a secondary battery, wherein the predetermined voltage is set to a voltage level at which a polarization voltage of the secondary battery is saturated. It is a device that determines the secondary battery from the estimated full charge capacity,
Charging means for charging the secondary battery at a constant current;
Means for continuously measuring the voltage of the secondary battery being charged;
Means for storing continuously measured voltage in association with charging time;
Means for calculating the voltage change rate with respect to the charging time from the data indicating the time change of the voltage of the secondary battery stored before that when the voltage of the continuously measured secondary battery reaches the predetermined voltage When,
A means for comparing the calculated voltage change rate with a threshold;
The discriminating apparatus, wherein the predetermined voltage is set to a voltage level at which a polarization voltage of the secondary battery is saturated.

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