JP2017143026A - Secondary battery soundness estimation method in system combining fuel cell and secondary battery, and system combining fuel cell and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide soundness estimation method and device of secondary battery capable of calculating the soundness of a secondary battery with high accuracy at a low cost, in a system combining a fuel cell and a secondary battery, and capable of improving the management accuracy of the secondary battery.SOLUTION: A soundness estimation method of secondary battery in a system combining a fuel cell and a secondary battery measures the open voltage (170, 270) by charging (130, 230) with different target charging rate, after two time use (100, 200) before and after a standby time, involving discharge from the secondary battery, calculates (180, 280) the charging rates (SOCv1, SOCv2) based thereon, obtains (280) the I/O current integration value between the two time open voltages, calculates (282) the current integration charging rate (ΔSOCi) based thereon, and estimates (284) the soundness SOH of the secondary battery from an expression :ΔSOCi/ΔSOCv=SOH, where the difference of two time open voltage charging rate is ΔSOCv, and the current integration charging rate is ΔSOCi.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for estimating the degree of soundness of a secondary battery in a system that uses both a fuel cell and a secondary battery, and a system that uses a fuel cell and a secondary battery together to implement the method.

  A fuel cell is a power generation device that extracts power by reacting fuel (such as hydrogen) with an oxidant (such as oxygen), and can be used continuously as a power source by replenishing the fuel, but output is low at low temperature startup. There is a problem that becomes stable. In addition, auxiliary power for supplying fuel and oxidant continuously to the fuel cell is also required.

  Therefore, it is advantageous to construct a power supply system that uses both a fuel cell and a secondary battery, and to use the secondary battery as a power source for starting and an auxiliary power source. In a vehicle equipped with such a system, it is required to grasp the charging rate (State of charge: SOC) and the state of health (State of health: SOH) of the secondary battery and manage the vehicle so as not to hinder driving.

  The SOH of the secondary battery can be obtained by measuring the battery capacity at the time of deterioration due to complete discharge from the fully charged state and calculating the ratio with the initial capacity, except for special cases such as inspection. It is difficult to fully 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 adopted.

  For example, Patent Document 1 discloses a deterioration determination map created in advance with measured values of voltage, temperature, and current measured in a constant current, constant output state during moisture scavenging inside the fuel cell by a compressor during discharge of the secondary battery. A method of fitting and determining the degradation level is disclosed. However, in this method, it is necessary to create a large number of deterioration maps for each actual operating condition such as temperature and SOC. In Patent Document 1, the deterioration degree of the secondary battery is determined in three stages. Although cases are shown, there is a limit to the degradation determination level subdivision.

  Moreover, this method has a problem that the soundness level of the secondary battery (SOH = battery capacity at the time of deterioration / initial battery capacity) cannot be obtained as a numerical value. Since the charging rate (SOC) of the secondary battery is obtained from the remaining capacity / battery capacity, when the secondary battery is deteriorated, if the SOH cannot be obtained, the charging rate (SOC) cannot be obtained accurately.

  On the other hand, instead of measuring the battery capacity at the time of deterioration due to complete discharge from the fully charged state, the charging rate based on the current integrated value in a certain section and the charging rate obtained from the open circuit voltage (OCV) (open voltage charging rate) There is also a method of estimating the SOH from the ratio to the difference of 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 relaxation state. Therefore, it was difficult to use except in special cases.

JP 2009-231197 A

  The present invention has been made in view of the above-mentioned points of the prior 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 possible to provide a secondary battery soundness estimation method and apparatus capable of improving the management accuracy of a secondary battery.

  In order to solve the above-mentioned problems, the present inventor has intensively studied, and as a result, paying attention to the recovery charge of the secondary battery performed in preparation for the next start after the stop of the system using both the fuel cell and the secondary battery. By providing a significant difference in the target charging rate for each recovery charge, the difference in open-circuit voltage charging rate and the current integrated charging rate during that period have values with significant magnitudes, and from these values, the secondary battery The present invention was conceived by obtaining the knowledge that the soundness level can be calculated with high accuracy.

That is, the present invention is a system using a fuel cell and a secondary battery in combination.
After two uses before and after the system standby time (100, 200), the secondary battery is charged to different target charging rates (130, 230), and the open circuit voltage is measured (170, 270), respectively. The open-circuit voltage charging rate (SOCv1, SOCv2) is calculated based on the open-circuit voltage (180, 280), and the input / output current integrated value between the two open-circuit voltage measurements is determined (280), and the current integrated The charge rate (ΔSOCi) is calculated (282), the difference between the two open-circuit voltage charge rates is ΔSOCv, the current integrated charge rate is ΔSOCi, and the secondary battery soundness SOH is
It is estimated from the equation: ΔSOCi / ΔSOCv = SOH (284).

  According to the above method, it is possible to accurately calculate the soundness of the secondary battery with a practical frequency using the recovery charge of the secondary battery normally performed in a system using both the fuel cell and the secondary battery, In addition to being able to obtain the secondary battery health level as a numerical value that can be directly used for calculating the charge rate (remaining capacity) and determining deterioration, there is no need for a deterioration map, and there is little introduction and operation cost. It is advantageous in improving accuracy.

Specifically, the method for estimating the soundness level of the secondary battery according to the present invention includes:
A method for estimating the health of a secondary battery in a system using both a fuel cell and a secondary battery,
Charging the secondary battery to a first target charging rate (130);
Measuring a first open circuit voltage at the first charging rate after the charging (170);
Calculating a first open-circuit voltage charging rate (SOCv1) based on the first open-circuit voltage;
Changing or setting the target charging rate to a second target charging rate different from the first target charging rate (138, 238);
The system being used with discharge from the secondary battery (200);
Charging the secondary battery to the second target charge rate (230);
Measuring a second open circuit voltage at the second target charge rate after the charging (270);
Calculating a second open-circuit voltage charging rate (SOCv2) based on the second open-circuit voltage (280);
Obtaining an input / output current integrated value (SOCi2) from the first open-circuit voltage measurement to the second open-circuit voltage measurement;
Calculating a current integrated charging rate (ΔSOCi) based on the current integrated value (282);
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). Estimating from the equation: ΔSOCi / ΔSOCv = SOH (284);
Is defined as a method for estimating the soundness level of a secondary battery.

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

In a preferred aspect of the method for estimating the soundness level of the secondary battery according to the present invention,
The step (130) of charging the secondary battery to a first target charge rate includes a first stop operation (110) after a first use (100) of the system with discharge from the secondary battery. ) And is performed by feeding from the fuel cell,
The step (180) of calculating the first open-circuit voltage charging rate is started by the next start-up operation (150) of the system,
The step (230) of charging the secondary battery to a second target charge rate includes a second stop operation (210) after a second use (200) of the system with discharge from the secondary battery. ) And is performed by feeding from the fuel cell,
Since the step (280) of calculating the second open-circuit voltage charging rate is started by the next start-up operation (250) of the system, it is automatically sound at an appropriate timing by normal operation. It is advantageous in performing degree estimation and deterioration management.

  In the present invention, it is preferable that the difference between the first open-circuit voltage charging rate and the second open-circuit voltage charging rate is 10% or more with a full charge as 100%. With this configuration, the difference in open-circuit voltage charging rate and the difference in current integrated charging rate have significant values, and the soundness can be calculated accurately and stably without the influence of measurement errors. It is advantageous.

  In the present invention, it is preferable that the first open-circuit voltage charging rate and the second open-circuit voltage charging rate are 70% or more with 100% full charge. In order to make up for the shortage of output of the fuel cell at start-up, the charge rate of the secondary battery needs to be sufficiently secured. If it is 70% or more, the soundness level is not impaired without impairing the function of such a system. Estimation can be performed.

Further, the present invention is a system using a fuel cell (3) and a secondary battery (2) in combination,
A power management device (4) for managing power generation of the fuel cell and charge / discharge of the secondary battery;
A battery management device (1) for managing the 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 a means (22) for measuring an open-circuit voltage of the secondary battery, a means (12) for calculating an open-circuit voltage charging rate based on the open-circuit voltage, and an integrated current value of the secondary battery. Including means (21, 11) for measuring the current and a means (11) for calculating the current integrated charging rate based on the current integrated value,
Means (10, 41) for changing or setting the target charge rate of the charge control means to at least different first and second target charge rates;
Measured with the first open-circuit voltage charge rate (SOCv1) based on the first open-circuit voltage measured in a state charged to the first target charge rate, and charged to the second target charge rate. The difference from the second open-circuit voltage charging rate (SOCv2) based on the second open-circuit voltage is ΔSOCv, and the second open-circuit voltage measurement from the first open-circuit voltage measurement measured by the current integrated value measuring means. And a soundness estimation means (10) for calculating the soundness SOH of the secondary battery from the equation: ΔSOCi / ΔSOCv = SOH, where ΔSOCi is the current integrated charge rate based on the input / output current integrated value up to It is also intended for systems characterized by.

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

  In the present invention, the steady state determining means includes means for determining the elapse of a predetermined time after completion of charging up to the target charging rate, or means for determining that the 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 that uses 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 It is advantageous in improving

It is a block diagram which shows the power supply system for vehicles which uses a fuel cell and a secondary battery together. It is a block diagram which shows the battery management unit in the vehicle power supply system which uses a fuel cell and a secondary battery together. It is a flowchart which shows the soundness estimation process of the secondary battery along operation | use of the power supply system for vehicles which uses the fuel cell and secondary battery which concern on this invention embodiment together. It is a flowchart which shows the recovery charge sequence of the power supply system for vehicles which uses the fuel cell and secondary battery which concern on this invention embodiment together. It is a graph which shows the charging rate change of the secondary battery in the vehicle power supply system which uses the fuel cell and secondary battery which concern on this invention embodiment together.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows main components constituting a power supply system for a vehicle that uses a fuel cell 3 and a secondary battery 2 together. A vehicle (fuel cell vehicle) equipped with this power supply system is connected to a fuel by a power management device 4. The electric power generated by the battery 3 and the electric power stored in the secondary battery 2 are controlled, and the drive motor 5 is driven to run. 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 as fuel (negative electrode active material) to the negative electrode. In addition, an oxidation-reduction reaction is caused by the catalyst supported on the membrane electrode assembly to obtain electric power. Electric power for operating auxiliary equipment such as a valve of the hydrogen tank 31 and the compressor 32 is supplied from the secondary battery 2. Supplied.

  When the fuel cell 3 is started, 1) low catalytic activity due to low temperature (about -30 to 45 ° C) compared to the operating temperature (about 60 ° C to 80 ° C), 2) low humidification in the solid polymer membrane Ion low conductivity due to being in a state 3) Excessive oxygen due to substitution of air on the positive electrode side during stoppage 4) Output of the fuel cell 3 due to reasons such as reduced catalyst activity due to poisoning substance coating on the catalyst surface Becomes unstable.

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

  FIG. 2 is a block diagram showing the BMU 1 in the vehicle power supply system using the fuel cell 3 and the secondary battery 2 together. The BMU 1 records current, voltage, temperature data, and SOC management (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 In order to be able to use it in a safe state by constantly monitoring current / voltage / battery temperature via the current sensor 21, voltage sensor 22 and temperature sensor 23 While managing the secondary battery 2, the secondary battery in response to the input / output request from the power management device 4 Perform two of the charge and discharge control.

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

  The secondary battery 2 is charged by regenerative power when the vehicle decelerates, but discharges to assist the output of the fuel cell 3 during sudden acceleration or uphill, so that the SOC is not always 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 the use range before the fuel cell 3 enters a steady state, which may cause a system stop.

  In order to avoid such a problem, the fuel cell vehicle incorporates a “recovery charge 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 an ECU (not shown) of the fuel cell vehicle, but the SOC management portion of the secondary battery is controlled by the BMU. The recovery charge mode will be described later.

  The SOH management is based on the soundness of the secondary battery 2 (SOH = battery capacity at the time of deterioration / initial battery capacity) based on SOCi (current integrated charging rate) and SOCv (open-circuit voltage charging rate), as will be described later. Estimate and determine if it is greater than or equal to a predetermined value. When SOH is less than a predetermined value, a deterioration alarm is output to prompt replacement of the secondary battery. The SOH gradually decreases from 1 at the time of a new product due to the capacity decrease accompanying the deterioration of the secondary battery. In the case of a lithium ion secondary battery, cycle deterioration due to repeated charge and discharge and storage deterioration due to storage are known, and in applications as a power source for vehicles, SOH is set to 0.8 or more, and a deterioration warning when it becomes less than 0.8 Is set to be issued.

  In the SOP management, chargeable / dischargeable power (State of power: SOP) of the secondary battery 2 is calculated, and charge / discharge control of the secondary battery is optimized. The SOP depends on the internal resistance of the secondary battery, and the internal resistance of the battery differs depending on SOH, SOC, and temperature. Therefore, an SOP map (table data) using these as parameters is prepared, and the estimated SOC value and the actual temperature measurement value are obtained. SOP is calculated by applying to the map. Therefore, accurate estimation of SOH and update as frequently as possible are indispensable for SOP management.

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

  In recovery charging, the secondary battery 2 is charged to the 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 using the power supply system (fuel cell vehicle). . This charging control is performed by the charging control unit 40 of the power management apparatus 4, but the SOH estimation algorithm 10 using recovery charging is implemented in the BMU 1, and the target charging rate 41 is set or updated by the SOH estimation algorithm 10.

  FIG. 3 is a flowchart showing a secondary battery soundness estimation process in accordance with the operation of the power supply system (fuel cell vehicle), and FIG. 5 is a graph showing changes in the secondary battery charging rate during the process. In the present invention, the target charge rate (SOC) in two consecutive recovery charges (130, 230) is set to different values, so that the open-circuit voltage charge rate difference (ΔSOCv = SOCv1-SOCv2) and the current integrated charge rate therebetween. SOH is calculated from the ratio of ΔSOCv and ΔSOCi so that the difference (ΔSOCi = SOCi1-SOCi2) has a significant value.

  Regarding the target charge rate difference (ΔSOC), SOH can theoretically be calculated as long as ΔSOC is not 0, but ΔSOCv is affected by voltage measurement error during OCV measurement, and ΔSOCi is current measurement error during current integration. Therefore, if ΔSOC is small, the ratio of ΔSOCv and ΔSOCi may be buried in an error. Therefore, from the viewpoint, the target charge rate difference (ΔSOC) should be large, but the SOC of the secondary battery 2 is set to a use upper limit SOC from the viewpoint of ensuring the safety of the battery and suppressing deterioration, A reasonable margin is also taken into consideration, such as overcharging. In addition, since the purpose of the recovery charge is to secure the assist power at the next start-up, it is desirable that the target charge rate of each time is as high as possible. In the present embodiment, from the later-described experiment, the target charge rate (SOC) of two times before and after is set to 70% and 80%, and the target charge rate difference (ΔSOC) = 10%.

  As described above, the OCV measurement timing (170, 270), which is the basis of the open-circuit voltage charging rate (SOCv), requires that the OCV measurement be performed in a no-load state and a polarization relaxation state. It takes several tens of minutes to several hours after the end of charge / discharge to reach the state. In the fuel cell vehicle, after the key is turned off (110, 210), the system goes to the recovery charge (130, 230) mode through the system check (120, 220). When the waiting time (from time t12 to t21 in FIG. 5, t22 to t31 in FIG. 5) has passed a predetermined time (several tens of minutes to several hours) until the next key ON (150, 250) is reached (160, 260) is optimal.

  The predetermined time after the recovery charge corresponds to the polarization relaxation time of the secondary battery, but since it varies depending on the battery type, charge / discharge history, temperature, SOC, SOH, the relaxation time is obtained for each temperature, SOC, SOH, and OCV It is variable according to the state at the time of measurement, or is set to the longest time under the expected condition. For example, in an example of a lithium ion secondary battery of SOC 70% · SOH 1.0, the relaxation time at −10 ° C. is 90 minutes compared to the relaxation time: 23 minutes at a temperature of 25 ° C. In addition, the relaxation time at SOH 0.93 is 60 minutes as compared to the relaxation time at 23 hours when SOH 1.0, temperature 25 ° C. and SOC 70%. Based on the target charging rate (for example, 70 to 80%) during vehicle operation, a predetermined time is set by estimating the relaxation time as 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 on the basis of the relaxation time at SOH 0.8 · temperature −10 ° C., which is expected to be the longest relaxation time under the above battery use conditions.

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

(Simulated charge / discharge test to verify target charge rate and SOH estimation accuracy)
Next, in order to verify the SOH estimation accuracy based on various setting examples of the target charging rate, 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. , Using the measured discharge capacity from the full charge, as shown in FIG. 5 (100, 200)-key OFF (110, 210)-recovery charge (130, 230)-complete stop (140, 240) The charge / discharge test simulating key ON (150, 250) was carried out as follows.

  However, the secondary battery is installed in a constant temperature bath at a temperature of 25 ° C., and instead of performing two recovery chargings, the open-circuit voltage charging rate (SOCv1) is measured by waiting for the initial SOC after the first recovery charging. And as the current integrated charging rate (SOCi1) updated based on it, charging / discharging simulating one run (200) from the key ON (150) is performed, and then significant with the initial SOC (= SOCv1 = SOCi1) The recovery charge (230) is performed to a target charge rate with a target charge rate difference (ΔSOC: 2, 5, 10, 15%), and after waiting time, OCV measurement (250, 270) is performed, and the initial SOC (= SOCv1 = SOCi1) and SOCv and SOCi after recovery charging (SOCv2 and SOCi2 in FIG. 5) to 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 charge 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) is simulated.

(1) Initial SOC Adjustment Charge / Discharge Initial SOC for confirming that 3 hours or more have passed since the last charge / discharge, measuring the terminal voltage, obtaining the current SOC by the OCV-SOC method, and conducting the test When there was a deviation (70, 72, 75, 80, 85%), charge / discharge for SOC adjustment was performed.

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

(3) Vehicle running simulation charge / discharge Simulating vehicle running, 10C discharge 3 seconds, 10C charge 3 seconds, 1C discharge 3 seconds, 1C charge 3 seconds, 15C discharge 3 seconds, 15C charge 3 seconds, 25C discharge 6 seconds, The basic pattern of 15 C charge for 3 seconds was repeated as one set, the SOC target value at the end of travel was set to 50%, charge and discharge were performed, and the current integrated value during charge and discharge was recorded sequentially.
In addition, 1C (C rate) is a current rate and a current value (A) / battery capacity (Ah) when a battery having a certain rated capacity is discharged at a constant current and discharge is completed in one hour.

(4) Standing Assuming key OFF (210) and system check (220) before recovery charge, the unit was left standing for 1 minute.

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

(6) Acquisition of SOCv2 and SOCi2 Assuming that the key is turned on (250) after being left overnight after the recovery charge (230), it is allowed to stand for a predetermined time (6 hours) after the recovery charge, and then the OCV measurement (270 ) To obtain SOCv2 from the OCV-SOC characteristics, and calculate the current integrated charging rate SOCi2 based on the current integrated value after (2) (280).

(7) Calculation of SOH Assuming that the current integrated value is ∫i (t) dt, ΔSOCi is expressed by the following equation 1.
ΔSOCi = SOCi1-SOCi2 = ∫i (t) dt / FCCi (Formula 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 (Formula 2)
Therefore, the estimated SOH value is calculated by the following equation 3 (282).
SOH = ΔSOCi / ΔSOCv
= [{∫i (t) dt} / FCCi] / [{∫i (t) dt} / FCC] (Formula 3)

(8) Test results Table 2 shows the difference between the SOH actual measurement value (= 0.92) obtained in advance by full discharge from full charge and the estimated SOH value obtained by the above equations 1 to 3, and ΔSOH. Shown in From this result, it can be seen that if the target charge rate difference ΔSOC is 10% or more with 100% full charge, an estimated SOH value equivalent to the actual measurement value can be obtained.

  In addition, overall, 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 obtained, but ΔSOC Is 10% or more, it is a sufficiently practical result even when the second target charging rate is relatively low, and in the operation as shown in FIG. 3 and FIG. It shows that continuous operation can be set alternately.

(Reflecting the acquired SOH estimated value to the BMU parameter)
Based on the estimated SOH value obtained through the above process, the SOH of the BMU 1 shown in FIG. 2 is updated (284) and further compared with a predetermined value (for example, 0.8). Is output (286) to prompt battery inspection / replacement. Further, based on the acquired SOH, the FCC value, the OCV-SOC characteristic (look-up table) for calculating the SOC, and the SOP calculation map used for the charge / discharge control of the power management apparatus 4 are updated. In addition, when the standby time for OCV measurement is variable, the basic parameter of the standby time is updated based on the SOH.

  In the above embodiment, the case where it is determined that the secondary battery 2 is in the polarization relaxation state when a predetermined time elapses after the recovery charge is shown. However, the steady state determination means 13 is mounted on the BMU 1, and the secondary battery 2 is It can also be configured to actually detect that it is in a steady state and shift to OCV measurement.

  As such a steady state determination means 13, a map (look-up table) is prepared in advance with the polarization relaxation time of the secondary battery as a parameter, temperature, SOC, SOH, etc., and the polarization relaxation time is determined from the situation at the time of determination. It can be implemented in an estimation mode or a mode in which it is determined that the terminal voltage (OCV) is in a steady state when the change per unit time of the terminal voltage (OCV) is equal to or less than a predetermined value (the OCV at that time is adopted).

  Moreover, it can also comprise so that polarization may be forcedly relieved by implementing the polarization relaxation time shortening process with respect to the secondary battery 2, and it may transfer to OCV measurement. As such a polarization relaxation time shortening process, for example, for a secondary battery, a single discharge and a single charge of a very short time (2 to 3 seconds) are continuously performed, and the current is cut off in a charged state, It can be implemented with a configuration 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 implemented in a fuel cell vehicle (HEV) equipped with a power supply system using both a fuel cell and a secondary battery has been described. However, the present invention is not limited to this. As well as electric vehicles (EVs), power systems for mobile objects such as automobiles, motorcycles, and electric outboard motors, as well as power systems for household and emergency power sources that use both fuel cells and secondary batteries Can also be implemented.

1 BMU (Battery Management Unit)
2 Secondary battery 3 Fuel cell 4 Power management device 5 Motor 10 SOH estimation 11 Current integrated charging rate 12 Open-circuit 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 health of a secondary battery in a system using both a fuel cell and a secondary battery,
After using the system for two times before and after sandwiching the standby time, charge the secondary battery to a different target charging rate, measure the open voltage, calculate the open voltage charging rate based on the respective open voltage, An input / output current integrated value between the two open-circuit voltage measurements is obtained, a current integrated charge rate is calculated based on the input / output current integrated value, a difference between the two open-circuit voltage charge rates is ΔSOCv, and the current integrated charge rate is ΔSOCi, The soundness SOH of the secondary battery,
Formula: ΔSOCi / ΔSOCv = Secondary battery soundness estimation method estimated from SOH. A method for estimating the health of a secondary battery in a system using both a fuel cell and a secondary battery,
Charging the secondary battery to a first target charge rate;
Measuring a first open circuit voltage at the first charge rate after the charging;
Calculating a first open-circuit voltage charging rate based on the first open-circuit voltage;
Changing or setting the target charging rate to a second target charging rate different from the first target charging rate;
The system is used with a 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 charge rate after the charging;
Calculating a second open-circuit voltage charging rate based on the second open-circuit voltage;
Obtaining an 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;
The difference between the first open-circuit voltage charging rate and the second open-circuit voltage charging rate is ΔSOCv, the current integrated charging rate is ΔSOCi, and the soundness SOH of the secondary battery is estimated from the equation: ΔSOCi / ΔSOCv = SOH And steps to
A method for estimating the soundness level of a secondary battery. The step of charging the secondary battery to a first target charge rate is initiated with a first stop operation after a first use of the system with discharge from the secondary battery, and the fuel It is carried out by power supply from the battery,
The step of calculating the first open-circuit voltage charging rate is started by a next startup operation of the system,
The step of charging the secondary battery to a second target charge rate is initiated with a second stop operation after a second use of the system with discharge from the secondary battery, and the fuel It is carried out by power supply from the battery,
The method for estimating the health level of the secondary battery according to claim 2, wherein the step of calculating the second open-circuit voltage charging rate is started by a further startup operation of the system.   4. The method for estimating the health level of a secondary battery according to claim 2, wherein a difference between the first open-circuit voltage charging rate and the second open-circuit voltage charging rate is 10% or more with a full charge as 100%. 5. .   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 with a full charge as 100%. Soundness estimation method. A system that uses both a fuel cell and a secondary battery,
A power management device that manages power generation of the fuel cell and charge / discharge of the secondary battery;
A battery management device for managing the state of the secondary battery,
The power management device includes charge control means for charging the secondary battery to a target charge rate,
The battery management device includes means for measuring an open voltage of the secondary battery, means for calculating an open voltage charging rate based on the open voltage, means for measuring an integrated current value of the secondary battery, and the current In a device including means for calculating a current integrated charging rate based on the integrated value,
Means for changing or setting the target charge rate of the charge control means to at least first and second target charge rates different from each other;
A first open-circuit voltage charge rate based on a first open-circuit voltage measured in a state charged to the first target charge rate, and a second measured in a state charged to the second target charge rate The difference from the second open-circuit voltage charging rate based on the open-circuit voltage is ΔSOCv, and the input / output current integration from the first open-circuit voltage measurement to the second open-circuit voltage measurement measured by the current integrated value measuring means The current integrated charging rate based on the value is ΔSOCi, and the soundness SOH of the secondary battery is
Soundness estimation means (10) calculated from the formula: ΔSOCi / ΔSOCv = SOH;
A system using a fuel cell and a secondary battery together.   The battery management device further includes a steady state determination unit that determines that the secondary battery is in a steady state after being charged up to a target charging rate, and when the secondary battery is determined to be in a steady state, The system using both the fuel cell and the secondary battery according to claim 6, wherein an open circuit voltage of the secondary battery is measured or acquired.   The steady state determining means includes means for determining the elapse of a predetermined time after completion of charging up to the target charging rate, or means for determining that the change in the open-circuit voltage has become a predetermined value or less. A system that uses the fuel cell according to claim 7 and a secondary battery in combination.

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