JP6631297B2 - Method of estimating soundness of secondary battery in system using both fuel cell and secondary battery, and system using both fuel cell and secondary battery - Google Patents

Description

  The present invention relates to a method for estimating the soundness of a secondary battery in a system using both a fuel cell and a secondary battery, and a system using both a fuel cell and a secondary battery for implementing the method.

  A fuel cell is a power generator that extracts power by reacting a fuel (such as hydrogen) with an oxidant (such as oxygen). The fuel cell can be used continuously as a power source by replenishing the fuel. There is a problem of becoming stable. Also, electric power for auxiliary equipment for continuously supplying fuel and oxidant to the fuel cell is required.

  Therefore, it is advantageous to construct a power supply system using both the fuel cell and the secondary battery, and to use the secondary battery as a power supply at the time of starting and a power supply for auxiliary equipment. In a vehicle equipped with such a system, it is required that the state of charge (SOC) and the state of health (SOH) of the secondary battery be grasped and managed so as not to hinder traveling.

  The SOH of a secondary battery can be obtained by measuring the battery capacity at the time of deterioration due to complete discharge from a fully charged state and calculating the ratio to the initial capacity. It is difficult to completely discharge from full charge during operation. Therefore, instead of directly obtaining the SOH of the secondary battery, a method of estimating the SOH from other parameters is employed.

  For example, Patent Literature 1 discloses that a constant current, a voltage, a temperature, and a current measured in a constant output state during a scavenging of moisture in a fuel cell by a compressor during discharge of a secondary battery are stored in a deterioration determination map created in advance. A method of fitting and determining the degradation level is disclosed. However, in this method, it is necessary to prepare a number of deterioration maps for each actual operating condition such as temperature and SOC, and Patent Literature 1 determines the degree of deterioration of the secondary battery in three stages. Although the case is shown, there is a limit in subdividing the deterioration determination level.

  In addition, this method has a problem that the soundness of the secondary battery (SOH = battery capacity at the time of deterioration / initial battery capacity) cannot be obtained as a numerical value. Since the state of charge (SOC) of the secondary battery is obtained from the remaining capacity / battery capacity, when the secondary battery has deteriorated, the SOH cannot be obtained without accurately obtaining the state of charge (SOC).

  On the other hand, instead of measuring the battery capacity at the time of deterioration due to complete discharge from the fully charged state, a change in the charge rate based on the current integrated value in a certain section and the charge rate (open-circuit charge rate) obtained from the open circuit voltage (OCV) ) Can be used to estimate the SOH. However, in this method, it is necessary to measure the open circuit voltage (OCV) before and after charging / discharging in a no-load state and in a polarization-relaxed state, and it takes tens of minutes to several hours after the end of charge / discharge to enter the polarization-relaxed state. Therefore, it was difficult to use it except in special cases.

JP 2009-231197 A

  The present invention has been made in view of the above points of the related art, and an object thereof is to calculate the soundness of a secondary battery with low cost and high accuracy in a system using both a fuel cell and a secondary battery. It is an object of the present invention to provide a method and an apparatus for estimating the soundness of a secondary battery that can improve the management accuracy of the secondary battery.

  In order to solve the above-mentioned problems, the present inventor has conducted intensive studies. As a result, the present inventors focused on the recovery charging of the secondary battery which is performed in preparation for the next start after stopping the system using both the fuel cell and the secondary battery. By providing a significant difference between the target charging rates of the recovery charging times, the difference between the open-circuit charging rate and the current integrated charging rate during that time becomes a value having a significant magnitude. The present inventors have found that the degree of soundness can be accurately calculated, and have arrived at the present invention.

That is, the present invention relates to a system using both a fuel cell and a secondary battery,
After two uses (100, 200) before and after the standby time of the system, the secondary battery is charged to different target charging rates (130, 230), and the open-circuit voltage is measured (170, 270). The open-circuit voltage charging rate (SOCv1, SOCv2) is calculated based on the open-circuit voltage (SOCv1, SOCv2) (180, 280), and the input / output current integrated value between the two open-circuit voltage measurements is obtained (280). A charge rate (ΔSOCi) is calculated (282), and a degree of health SOH of the secondary battery is defined assuming that a difference between the two open-circuit charge rates is ΔSOCv and the integrated current charge rate is ΔSOCi.
Equation (284): Estimate from ΔSOCi / ΔSOCv = SOH (284).

  According to the above method, the soundness of the secondary battery can be accurately calculated at a practical frequency using recovery charging of the secondary battery usually performed in a system using both the fuel cell and the secondary battery, and In addition to being able to obtain the degree of soundness of the secondary battery as a numerical value that can be directly used for calculating the charge rate (remaining capacity) and determining deterioration, a deterioration map is not required, and the introduction and operation costs are low, and the management of the secondary battery This is advantageous in improving accuracy.

The method for estimating the soundness of a secondary battery according to the present invention is specifically,
A method for estimating the soundness of a secondary battery in a system using both a fuel cell and a secondary battery,
After a first use (100) of the system with discharging from the secondary battery,
Charging the secondary battery to a first target charging rate (130);
Measuring a first open circuit voltage at the first target charging rate after the charging (170);
Calculating a first open-circuit voltage charging rate (SOCv1) based on the first open-circuit voltage (180);
Changing or setting the target charging rate to a second target charging rate different from the first target charging rate (138, 238);
After a second use (200) of the system with discharging from the secondary battery,
Charging the secondary battery to the second target charging rate (230);
Measuring a second open circuit voltage at the second target charging rate after the charging (270);
Calculating a second open-circuit voltage charging rate (SOCv2) based on the second open-circuit voltage (280);
A step (280) of obtaining an input / output current integrated value (SOCi2) from the first open-circuit voltage measurement to the second open-circuit voltage measurement;
Calculating (282) a current integrated charging rate (ΔSOCi) based on the current integrated value;
Assuming that the difference between the first open-circuit voltage charging rate (SOCv1) and the second open-circuit voltage charging rate (SOCv2) is (ΔSOCv), and the current integrated charging rate is (ΔSOCi), the degree of health SOH of the secondary battery is (284) is estimated from the equation: ΔSOCi / ΔSOCv = SOH.

  As is clear from the above, the estimation of the soundness can be performed during the normal operation of the system, and the calculated values are parameters common to the charge rate management of the secondary battery, and the SOC management and the SOH management are performed. There is an advantage that it can be implemented comprehensively in parallel.

In a preferred aspect of the method for estimating the soundness of a secondary battery according to the present invention,
The step (130) of charging the secondary battery to a first target charging rate comprises a first stop operation (110) after a first use (100) of the system with a discharge from the secondary battery. ) And is implemented by power supply from the fuel cell,
The step (180) of calculating the first open-circuit charge rate is started by a next start-up operation (150) of the system;
The step (230) of charging the secondary battery to a second target charge rate comprises a second shutdown operation (210) after a second use (200) of the system with discharging from the secondary battery. ) And is implemented by power supply from the fuel cell,
The step (280) of calculating the second open-circuit charging rate is started by the next start-up operation (250) of the system. This is advantageous in performing degree estimation and deterioration management.

  In the present invention, it is preferable that a difference between the first open-circuit voltage charging rate and the second open-circuit voltage charging rate is 10% or more when a full charge is 100%. With this configuration, the difference between the open-circuit charging rate and the difference between the current integrated charging rates has a significant value, and the accuracy of the soundness can be calculated with high accuracy and stability while eliminating the influence of the measurement error. It is advantageous.

  In the present invention, it is preferable that each of the first open-circuit voltage charging rate and the second open-circuit voltage charging rate is 70% or more when a full charge is 100%. In order to compensate for the insufficient output of the fuel cell at the time of starting, it is necessary that the charging rate of the secondary battery is sufficiently ensured. If it is 70% or more, the soundness of such a system is maintained without impairing the function of such a system. An estimate can be made.

Further, the present invention relates to a system using both a fuel cell (3) and a secondary battery (2),
A power management device (4) for managing power generation of the fuel cell and charging / discharging of the secondary battery;
A battery management device (1) for managing a state of the secondary battery,
The power management device (4) includes charging control means (40) for charging the secondary battery to a target charging rate,
The battery management device (1) includes means (22) for measuring an open voltage of the secondary battery, means (12) for calculating an open voltage charging rate based on the open voltage, and an integrated current value of the secondary battery. means for measuring (21, 11), and, seen including means (11) for calculating a current integration SOC based on the current integrated value,
In a configuration in which the recovery charge is performed when the charge rate is equal to or less than a predetermined value after use of the system ,
Means for storing the target charging rate after the completion of the recovery charge, to change from the first target charging rate to a second target charging rate, the changed target charging rate to the next recovery charge (10,41) When,
A first open-circuit voltage charging rate (SOCv1) based on the first open-circuit voltage measured in a state charged to the first target charging rate, and measured in a state charged to the second target charging rate. The difference from the second open-circuit voltage charging rate (SOCv2) based on the second open-circuit voltage is ΔSOCv, the second open-circuit voltage measurement from the first open-circuit voltage measurement measured by the current integrated value measuring means. And a soundness estimating means (10) for calculating a soundness SOH of the secondary battery from an equation: ΔSOCi / ΔSOCv = SOH, where ΔSOCi is a current integrated charging rate based on the input / output current integrated value up to and including It is also intended for systems characterized by.

  In the present invention, the battery management device (1) further includes a steady state determining means (13) for determining that the secondary battery is in a steady state after charging to a target charging rate, wherein the secondary battery is in a steady state. Preferably, when it is determined that the open circuit voltage is determined, the open circuit voltage of the secondary battery is measured or obtained.

  In the present invention, the steady state determining unit includes a unit that determines a lapse of a predetermined time after the completion of charging up to the target charging rate, or a unit that determines that a change in the open-circuit voltage has become a predetermined value or less. be able to.

  Since the present invention is configured as described above, in a system using both a fuel cell and a secondary battery, the soundness of the secondary battery can be calculated with low cost and high accuracy, and the management accuracy of the secondary battery can be calculated. It is advantageous in improving.

FIG. 2 is a block diagram showing a vehicle power supply system using both a fuel cell and a secondary battery. FIG. 3 is a block diagram showing a battery management unit in a vehicle power supply system using both a fuel cell and a secondary battery. 5 is a flowchart illustrating a process of estimating the soundness of a secondary battery along with the operation of a vehicle power supply system using both a fuel cell and a secondary battery according to an embodiment of the present invention. 4 is a flowchart illustrating a recovery charging sequence of the vehicle power supply system using both the fuel cell and the secondary battery according to the embodiment of the present invention. 4 is a graph showing a change in a charging rate of a secondary battery in a vehicle power supply system using both a fuel cell and a secondary battery according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows main components constituting a vehicle power supply system using both a fuel cell 3 and a secondary battery 2. A vehicle equipped with this power supply system (fuel cell vehicle) is controlled by a power management device 4 to provide fuel. The power generated by the battery 3 and the power stored in the secondary battery 2 are controlled to drive the drive motor 5 to travel. When the vehicle decelerates, the regenerative power is charged in the secondary battery 2.

  The fuel cell 3 (fuel cell stack) supplies oxygen in the air as an oxidant (positive electrode active material) to the positive electrode by the compressor 32 and supplies hydrogen from the hydrogen tank 31 to the negative electrode as fuel (negative electrode active material). In addition, an electric power is obtained by causing an oxidation-reduction reaction by a catalyst supported on the membrane electrode assembly, and electric power for operating auxiliary equipment such as a valve of the hydrogen tank 31 and a compressor 32 is supplied from the secondary battery 2. Supplied.

  When the fuel cell 3 is started, 1) low catalytic activity due to a low temperature (about -30 to 45 ° C.) compared to an operating temperature (about 60 ° C. to 80 ° C.) 2) low humidification inside the solid polymer membrane Low ion conductivity due to the state, 3) excessive oxygen due to air being replaced on the positive electrode side during shutdown, 4) output of fuel cell 3 due to reduced catalytic activity due to coating of poisoning substances on the catalyst surface, etc. Becomes unstable.

  Therefore, the secondary battery 2 is used as a power source for the drive motor 5 immediately after the start-up and until the fuel cell 3 enters a steady operation state, so that the vehicle can be immediately driven normally after key-on. ing. The secondary battery 2 is controlled by a battery management unit (BMU: Battery management unit) so as to be charged and discharged within a predetermined usage range (for example, SOC: 30 to 70%). At times, it is desirable to keep the SOC of the secondary battery 2 close to the upper limit of use for the above-described reason.

  FIG. 2 is a block diagram showing a BMU 1 in a vehicle power supply system using both the fuel cell 3 and the secondary battery 2. The BMU 1 records current, voltage, and temperature data, and manages SOC (SOC estimation algorithm / table data). , ROM for storing programs for executing SOH management (SOH estimation algorithm), SOP management (SOP estimation algorithm / table data), current / voltage / temperature upper / lower limit management, cell balance control, etc., CPU for arithmetic processing, data recording The current / voltage / battery temperature is constantly monitored via a current sensor 21, a voltage sensor 22, and a temperature sensor 23, and the basic routine is used so that the device can be used in a safe state. While managing the secondary battery 2, the secondary battery is operated in response to an input / output request from the power management device 4. Perform two of the charge and discharge control.

  In the SOC management, the charging rate (SOC = remaining capacity / battery capacity) of the secondary battery is estimated from the integrated current value and the OCV-SOC characteristic. The remaining amount is displayed using SOCi (current integrated charging rate) obtained by dividing the sum of the current integrated value during charging and discharging measured by the current sensor 21 and the initial remaining amount by the battery capacity. Since a measurement error of the integrated current accumulates in a long-time operation, the SOCv is determined from the OCV-SOC characteristic based on the open circuit voltage (OCV) measured by the voltage sensor 22 in the no-load and depolarized state at the time of key-on after the predetermined standby time. (Open-circuit voltage charging rate) is calculated, and the SOC is corrected. Since the battery capacity decreases due to the deterioration of the secondary battery, accurate estimation of the SOH and update as frequently as possible are indispensable for SOC management.

  The rechargeable battery 2 is charged by regenerative power when the vehicle decelerates, but is discharged in order to assist the output of the fuel cell 3 during rapid acceleration or uphill, so that the SOC is not necessarily in a high state after traveling. Absent. If the fuel cell 3 is started in a state where the SOC of the secondary battery 2 is low, the SOC of the secondary battery 2 falls below a use range before the fuel cell 3 becomes in a steady state, and there is a possibility that the system may be stopped.

  In order to avoid such a problem, the fuel cell vehicle is provided with a “recovery charging mode” for maintaining the SOC of the secondary battery at the time of startup near the upper limit of use. In the recovery charging mode, the charging sequence shown in FIG. 4 is controlled and executed by the ECU of the fuel cell vehicle (not shown), but the SOC management part of the secondary battery is controlled by the BMU. The recovery charging mode will be described later.

  In the SOH management, the degree of soundness of the secondary battery 2 (SOH = battery capacity at the time of deterioration / initial battery capacity) is determined based on SOCi (current integrated charging rate) and SOCv (open voltage charging rate), as described later. It is estimated and it is determined whether or not it is equal to or more than a predetermined value. If the SOH is less than the predetermined value, a deterioration alarm is output to urge replacement of the secondary battery. The SOH gradually decreases from 1 at the time of a new product due to a decrease in capacity due to deterioration of the secondary battery. In the case of lithium ion secondary batteries, cycle deterioration due to repeated charging and discharging and storage deterioration due to storage are known. For use as a vehicle power supply, the SOH is set to 0.8 or more, and when it is less than 0.8, a deterioration alarm is issued. Is set to be issued.

  The SOP management calculates the chargeable / dischargeable power (State) of the secondary battery 2 (SOP) and optimizes the charge / discharge control of the secondary battery. Since the SOP depends on the internal resistance of the secondary battery, and the internal resistance of the battery differs depending on the SOH, SOC, and temperature, an SOP map (table data) using these parameters as parameters is prepared, and the estimated SOC and measured temperature are calculated. The SOP is calculated by applying to the map. Therefore, accurate estimation of the SOH and updating as frequently as possible are essential for SOP management.

  Next, the SOH estimation using the recovery charge, which is the subject of the present invention, will be described.

  In the recovery charging, the secondary battery 2 is charged to a target charging rate by constant current control or constant voltage control using the generated power of the fuel cell 3 in preparation for the next use after the use of the power supply system (fuel cell vehicle). . This charge control is performed by the charge control unit 40 of the power management apparatus 4. The SOH estimation algorithm 10 using the recovery charge is mounted on the BMU 1, and the target charge rate 41 is set or updated by the SOH estimation algorithm 10.

  FIG. 3 is a flowchart illustrating a process of estimating the soundness of the secondary battery along with the operation of the power supply system (fuel cell vehicle), and FIG. 5 is a graph illustrating a change in the charging rate of the secondary battery during the process. In the present invention, the target charging rate (SOC) in two consecutive recovery chargings (130, 230) is set to different values, so that the open-circuit charging rate difference (ΔSOCv = SOCv1-SOCv2) and the current integrated charging rate The SOH is calculated from the ratio between ΔSOCv and ΔSOCi such that the difference (ΔSOCi = SOC1−SOCi2) has a significant value.

  For the target charging rate difference (ΔSOC), SOH can theoretically be calculated as long as ΔSOC is not 0. However, ΔSOCv is affected by the voltage measurement error during OCV measurement, and ΔSOCi is the current measurement error during current integration. Therefore, if ΔSOC is small, the ratio between ΔSOCv and ΔSOCi may be buried in an error. Therefore, from this viewpoint, it is better that the target charging rate difference (ΔSOC) is large. However, the SOC of the secondary battery 2 is set to the upper limit SOC in view of ensuring the safety of the battery and suppressing deterioration. An appropriate margin is also taken into account, assuming overcharging and the like. In addition, since the purpose of the recovery charging is to secure the assist power at the next start-up, it is desirable that the target charging rate of each time be as high as possible. In the present embodiment, based on experiments to be described later, the target charging rates (SOC) before and after twice are set to 70% and 80%, and the target charging rate difference (ΔSOC) = 10%.

  As described above, the OCV measurement needs to be performed in the no-load state and the depolarized state as described above for the OCV measurement timing (170, 270) based on the open-circuit charge rate (SOCv). It takes several tens minutes to several hours after the end of charging and discharging to reach the state. In the fuel cell vehicle, after the key is turned off (110, 210), the system shifts to the recovery charging (130, 230) mode through the system check (120, 220), so that the recovery charging is completed and the vehicle is completely stopped (140, 240). When the standby time until the next key ON (150, 250) after the time (time interval t12 to t21, interval t22 to t31 in FIG. 5) exceeds a predetermined time (several minutes to several hours) (160, 160). 260) is optimal.

  The predetermined time after the recovery charge corresponds to the polarization relaxation time of the secondary battery, but differs depending on the type of battery, charge / discharge history, temperature, SOC, and SOH. Therefore, the relaxation time is obtained for each temperature, SOC, and SOH. It is variable depending on the state at the time of measurement, or set to the longest time under the expected conditions. For example, in the case of a lithium ion secondary battery having an SOC of 70% and SOH of 1.0, the relaxation time at -10 ° C. is 90 minutes, while the relaxation time at 25 ° C. is 23 minutes. Further, the relaxation time at 0.93 hours of SOH is 60 minutes, while the relaxation time at 1.0 hours of SOH, 25 ° C. and 70% SOC is 23 minutes. Based on a target charging rate during vehicle operation (for example, 70 to 80%), a predetermined time is set by estimating a relaxation time with an assumed temperature range of 0 to 35 ° C. and an SOH range of 1.0 to 0.8. Alternatively, the predetermined time may be set based on the relaxation time at SOH 0.8 at a temperature of −10 ° C., where the relaxation time is expected to be the longest under the above-mentioned battery use conditions.

  The recovery charge mode is executed by the ECU of the fuel cell vehicle (not shown) according to a charge sequence as shown in FIG. When the charging sequence is started (131), BMU1 is updated and stored at the previous recovery charging and the stored target charging rate is obtained (132) and compared with the current SOC (133). If the current SOC is higher than the target charging rate, the recovery sequence is not performed, and the charging sequence ends. If the current SOC is less than the target charging rate, a required charging amount is calculated based on the difference between the current SOC and the target charging rate (134), and a charging time at a predetermined C rate is calculated (135). Recovery charging is started by the power management device 4 under constant current control (136). When the charging is completed (137), the target charging rate is updated for the next recovery charging (138) and stored in the memory of the BMU1. When the charging sequence is completed, the power of the system is turned off and the system is completely stopped (139).

(Simulated charge / discharge test to verify target charging rate and SOH estimation accuracy)
Next, in order to verify the SOH estimation accuracy based on the setting examples of various target charging rates, a deteriorated cell (SOH: 0.93) of a 3 Ah class lithium ion battery (rated capacity 2.9 Ah, manufactured by Toshiba) as a secondary battery was used. Using the actual measured values of the discharge capacity from the full charge, the traveling (100, 200) to the key OFF (110, 210) to the recovery charge (130, 230) to the complete stop (140, 240) as shown in FIG. ) To a key ON (150, 250) were performed as follows.

  However, the secondary battery is placed in a thermostat at a temperature of 25 ° C., and instead of performing the recovery charging twice, an open-circuit voltage charging rate (SOCv1) measured after a standby time after the initial recovery charging of the initial SOC. And charge / discharge simulating one run (200) from key ON (150) as a current integrated charging rate (SOCi1) updated based on the current integrated charging rate (SOCi1). Thereafter, the initial SOC (= SOCv1 = SOCi1) is significant. Recovery charging (230) is performed up to a target charging rate having a target charging rate difference (ΔSOC: 2, 5, 10, 15%). After a standby time, OCV measurement (250, 270) is performed, and the initial SOC (= From the SOCv1 = SOCi1 and the SOCv and the SOCi after the recovery charge (SOCv2 and SOCi2 in FIG. 5), ΔSOC (= initial SOC−SOCv2) and ΔSOCi (= initial SOC) SOCi2) asking was calculated SOH from the ratio of ΔSOCV and DerutaSOCi.

Table 1 shows the recovery charging conditions. In Table 1, the initial SOC simulates the SOC (SOCv1, SOCi1) at the first key ON (150) in FIG. 5, and the target charging rate is the SOC at the second key ON (250) in FIG. (SOCv2, SOCi2).

(1) Initial SOC adjustment charge / discharge After confirming that three hours or more have elapsed since the last charge / discharge, measure the terminal voltage, obtain the current SOC by the OCV-SOC method, and execute the test. (70, 72, 75, 80, 85%), charge / discharge for SOC adjustment was performed.

(2) Acquisition of SOCv1 and SOCi1 The terminal voltage measurement value after standing for 3 hours after the adjustment charging / discharging is defined as OCV, the open-circuit voltage charging rate SOCv1 is obtained from the OCV-SOC characteristic, and the current integrated charging rate is determined based on the SOCv1. (SOCi1 = SOCv1) was updated (180).

(3) Vehicle running simulation charge / discharge Simulates running of the vehicle, and discharges 10C for 3 seconds, 10C for 3 seconds, 1C for 3 seconds, 1C for 3 seconds, 15C for 3 seconds, 15C for 3 seconds, 25C for 6 seconds, The charge / discharge was performed with the SOC target value at the end of traveling being 50%, and the integrated current value during the charge / discharge was sequentially recorded.
1C (C rate) is a current rate and a current value (A) / battery capacity (Ah) in a case where a battery having a certain rated capacity is discharged at a constant current and discharge is completed in one hour.

(4) Stationary Assuming the key OFF (210) and the system check (220) before recovery charging, the apparatus was allowed to stand for 1 minute.

(5) Recovery charge simulated charge Recovery charge (230) was simulated and charged at a 10C rate. The target charging rate in the recovery charging was set to the initial SOC ± 2, 5, 10, and 15% as shown in Table 1. During this time, the sequential recording of the current integrated value is continued.

(6) Acquisition of SOCv2 and SOCi2 It is assumed that the key is turned on (250) after being left overnight after the recovery charge (230), and then left for a predetermined time (6 hours) after the recovery charge, and then the OCV measurement (270) ), SOCv2 was obtained from the OCV-SOC characteristic, and the current integrated charging rate SOCi2 was calculated based on the current integrated value after (2) (280).

(7) Calculation of SOH Assuming that the integrated current value is ∫i (t) dt, ΔSOCi is expressed by the following equation 1.
ΔSOCi = SOC1−SOCi2 = ∫i (t) dt / FCCi (Equation 1)
When the current integrated value ∫i (t) dt is used, ΔSOCv is expressed by the following equation 2.
ΔSOCv = SOCv1-SOCv2 = ∫i (t) dt / FCC (Equation 2)
Therefore, the SOH estimation value is calculated by the following equation 3 (282).
SOH = ΔSOCi / ΔSOCv
= [{I (t) dt} / FCCi] / [{i (t) dt} / FCC] (Equation 3)

(8) Test Results Table 2 shows the difference between the actual measured SOH value (= 0.92) previously obtained by complete discharge from full charge and the estimated SOH value obtained by the above formulas 1 to 3, and ΔSOH. Shown in From this result, it can be seen that if the difference ΔSOC between the target charging rates is 10% or more with the full charge being 100%, an SOH estimated value equivalent to the actually measured value can be obtained.

  On the whole, when the target charging rate is higher than the initial SOC, that is, when the second target charging rate in the two recovery chargings before and after is higher, a slightly better result is shown. Is 10% or more, a sufficiently practical result is obtained even when the second target charging rate becomes relatively low. In the operation shown in FIGS. This indicates that continuous operation can be set alternately.

(Reflection of the acquired SOH estimation value to the parameters in the BMU)
The SOH of the BMU 1 shown in FIG. 2 is updated (284) based on the estimated SOH value obtained through the above process, and is compared with a predetermined value (for example, 0.8). Is output (286) to urge battery inspection and replacement. Further, based on the acquired SOH, the FCC value, the OCV-SOC characteristic (lookup table) for SOC calculation, and the SOP calculation map used for charge / discharge control of the power management device 4 are updated. When the standby time for the OCV measurement is variable, the basic parameter of the standby time is updated based on the SOH.

  In the above-described embodiment, the case has been described where it is determined that the secondary battery 2 is in the polarization relaxation state when a predetermined time has elapsed after the recovery charge. However, the steady state determination unit 13 is mounted on the BMU 1 and the secondary battery 2 It is also possible to configure so as to actually detect that it is in a steady state and to shift to OCV measurement.

  Such a steady state determination means 13 prepares a map (look-up table) in advance by using the polarization relaxation time of the secondary battery as a parameter such as temperature, SOC, SOH, and the like, and determines the polarization relaxation time from the situation at the time of determination. The present invention can be implemented in a mode of estimating or in a mode of determining a steady state when the change in terminal voltage (OCV) per unit time becomes equal to or less than a predetermined value (using the OCV at that time).

  Further, it is also possible to perform a polarization relaxation time shortening process on the secondary battery 2 to forcibly relax the polarization and shift to the OCV measurement. As such a polarization relaxation time shortening process, for example, a single-shot discharge and a single-shot charge for a very short time (2 to 3 seconds) are continuously performed on a secondary battery, and a current is cut off in a charged state. This can be implemented in a configuration in which the circuit is in an open circuit state.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention.

  For example, in the above embodiment, the case where the present invention is applied to a fuel cell vehicle (HEV) equipped with a power supply system using both a fuel cell and a secondary battery is described, but the present invention is not limited to this. Not only, as a power supply system for electric vehicles (EV), but also for mobile objects such as automobiles, motorcycles, and electric outboard motors, and as a power supply system for home and emergency power supplies that use both fuel cells and secondary batteries Is also feasible.

1 BMU (battery management unit)
2 Rechargeable battery 3 Fuel cell 4 Power management device 5 Motor 10 SOH estimation 11 Current integrated charging rate 12 Open voltage charging rate 13 Steady state determination 21 Current sensor 22 Voltage sensor 23 Temperature sensor 40 Charge / discharge control 41 Target charging rate

Claims (8)

A method for estimating the soundness of a secondary battery in a system using both a fuel cell and a secondary battery,
After two uses before and after the standby time of the system, the rechargeable battery is charged to a different target charging rate to measure an open-circuit voltage, and an open-circuit voltage charging rate is calculated based on each open-circuit voltage. An input / output current integrated value between the two open-circuit voltage measurements is obtained, a current integrated charging rate is calculated based on the input / output current integrated value, a difference between the two open-circuit voltage charging rates is ΔSOCv, and the current integrated charging rate is ΔSOCi, Degree of health SOH of the secondary battery,
Formula: A method of estimating the degree of soundness of the secondary battery, which is estimated from ΔSOCi / ΔSOCv = SOH. A method for estimating the soundness of a secondary battery in a system using both a fuel cell and a secondary battery,
After a first use of the system with a discharge from the secondary battery,
Charging the secondary battery to a first target charging rate;
Measuring a first open circuit voltage at the first target charging rate after the charging;
Calculating a first open voltage charging rate based on the first open voltage;
Changing or setting the target charging rate to a second target charging rate different from the first target charging rate,
And implement
After a second use of the system with discharge from the secondary battery,
Charging the secondary battery to the second target charging rate;
Measuring a second open circuit voltage at the second target charging rate after the charging;
Calculating a second open-circuit voltage charging rate based on the second open-circuit voltage;
Determining the input / output current integrated value from the first open-circuit voltage measurement to the second open-circuit voltage measurement,
Calculating a current integrated charging rate based on the current integrated value;
Assuming that the difference between the first open-circuit voltage charging rate and the second open-circuit voltage charging rate is ΔSOCv and the integrated current charging rate is ΔSOCi, the soundness SOH of the secondary battery is estimated from the equation: ΔSOCi / ΔSOCv = SOH. Steps to
And a method for estimating the soundness of a secondary battery. Charging the rechargeable battery to a first target charge rate begins with a first shut-down operation after a first use of the system with discharging from the rechargeable battery; and Powered by batteries,
The step of calculating the first open-circuit voltage charging rate is started by a next startup operation of the system,
Charging the rechargeable battery to a second target charge rate begins with a second shutdown operation after a second use of the system with discharging from the rechargeable battery; and Powered by batteries,
3. The method according to claim 2, wherein the step of calculating the second open-circuit voltage charging rate is started by a next startup operation of the system. 4.   The health estimation method for a secondary battery according to claim 2 or 3, wherein a difference between the first open-circuit voltage charging rate and the second open-circuit voltage charging rate is 10% or more when a full charge is 100%. .   5. The secondary battery according to claim 2, wherein each of the first open-circuit voltage charging rate and the second open-circuit voltage charging rate is 70% or more when a full charge is 100%. Health estimation method. A system that uses a fuel cell and a secondary battery together,
A power management device that manages power generation of the fuel cell and charge / discharge of the secondary battery,
A battery management device that manages the state of the secondary battery,
The power management device includes charging control means for charging the secondary battery to a target charging rate,
The battery management device includes a unit configured to measure an open-circuit voltage of the secondary battery, a unit configured to calculate an open-circuit charge rate based on the open-circuit voltage, a unit configured to measure an integrated current value of the secondary battery, and the current. Including means for calculating a current integrated charging rate based on the integrated value,
In a configuration in which the recovery charge is performed when the charge rate is equal to or less than a predetermined value after use of the system,
Means for changing the target charging rate after the completion of the recovery charging, from the first target charging rate to the second target charging rate, and storing the changed target charging rate until the next recovery charging;
A first open-circuit voltage charging rate based on a first open-circuit voltage measured in a state charged to the first target charging rate, and a second open-circuit voltage charging rate measured in a state charged to the second target charging rate Is the difference between the second open-circuit voltage charging rate based on the open-circuit voltage and ΔSOCv, the input / output current integration from the first open-circuit voltage measurement to the second open-circuit voltage measurement measured by the current integration value measuring means. Assuming that the current integrated charging rate based on the value is ΔSOCi, the health SOH of the secondary battery is
Soundness estimating means calculated from the equation: ΔSOCi / ΔSOCv = SOH;
A system using both a fuel cell and a secondary battery, comprising:   The battery management device further includes a steady state determination unit that determines that the secondary battery is in a steady state after charging to a target charging rate, and when it is determined that the secondary battery is in a steady state, The system according to claim 6, wherein the open-circuit voltage of the secondary battery is measured or obtained.   The steady state determination means includes means for determining the elapse of a predetermined time after completion of charging up to the target charging rate, or including means for determining that the change in the open-circuit voltage has become a predetermined value or less. A system using both the fuel cell according to claim 7 and a secondary battery.

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