JP2007122882A - Charge state balance recovery method of battery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charge state balance recovery method of a battery system realizing reduction in size and weight in comparison with a battery system performance. <P>SOLUTION: This is the charge state balance recovery method of the battery system in which a high output battery (10) that has a small internal resistance (R1) and has a small capacity, and in which a high capacity battery (20) that has a larger internal resistance (R2) than that of the high output battery and has a larger capacity than that of the high output battery are connected in parallel. By an appropriate combination of characteristics of the high output battery and the high capacity battery [state of charge (SOC)-open circuit voltage], the charge state balance between the high output battery and the high capacity battery is made to be recovered promptly. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for recovering the state of charge of a battery system that can sufficiently meet the demand for instantaneous high loads and the repeated supply of continuous loads, and that can be reduced in size and weight.

Conventionally, in a battery system mounted on a vehicle such as an electric vehicle or a hybrid vehicle, a high-output secondary battery and a high-capacity secondary battery having different open circuit voltages are arranged in parallel as described in Patent Document 1 below. There is something connected. In this way, by changing the open circuit voltage of the high-power secondary battery and the high-capacity secondary battery, there is a demand to obtain a high energy density while maintaining a high power density above a certain level, or a high energy above a certain level. At the same time, it is possible to meet the demand to obtain a high output density while maintaining the density.
Japanese Patent Laid-Open No. 2004-111242

  However, the conventional battery system can sufficiently cope with temporary demands of momentary high load and continuous load, but frequent repetition of momentary high load and sustained load. There is still not enough to respond to requests. For example, when a vehicle such as an electric vehicle or a hybrid vehicle repeats overtaking while climbing up, recovery of a high-power secondary battery that is responsible for instantaneous high load cannot keep up with repeated high load demands. There is a case. This is because the high-power secondary battery has sufficient discharge characteristics, but the regenerative power charging characteristics are still insufficient. Insufficient charging characteristics of the high power density secondary battery cause a delay in the recovery of the battery system, giving the driver a feeling of insufficient power performance.

  The present invention has been made in view of such a conventional problem, and even when a request for an instantaneous high load or a request for a continuous load is frequently repeated, a high output secondary battery and a high capacity are provided. Rechargeable batteries can be made uniform in a short time in order to facilitate the quick recovery of the battery system, thereby improving the power performance of the vehicle and reducing the size and weight of the battery system compared to the performance of the battery system. An object of the present invention is to provide a method for recovering the state of charge balance of a battery system.

  In order to apply a secondary battery to a vehicle, it is necessary to be lightweight and compact. As a means for realizing a battery having a high output and a high capacity, the invention described in Patent Document 1 has been made. According to the present invention, a high-power battery and a high-capacity battery having different open-circuit voltages from a state of charge (SOC) are connected in parallel to reduce weight and size. In the invention described in Patent Document 1, the output (discharge) characteristic is excellent, but the input (charge) characteristic is inferior. At the time of considering the present invention, since a battery with high output density was considered, a method like the invention described in Patent Document 1 was considered, but in a secondary battery mounted on a hybrid vehicle or an electric vehicle, Charging characteristics are also required because it is necessary to accept regenerative power from the motor during deceleration and increase energy efficiency. Considering not only the output characteristics but also the input characteristics, the present invention increases the size of the battery. Therefore, a battery system in which batteries having the same open-circuit voltage with respect to the state of charge SOC are connected in parallel was considered.

  In addition, as a technique for connecting a high-power battery and a high-capacity battery in parallel, a technique in which an electric double layer capacitor is applied instead of the high-power battery can be considered. Here, an electric double layer capacitor is assumed that 160 single cells having a capacity of 1300F and a specific resistance of 2.4Ω · F are connected in series and charged to a charge amount of 80%. On the other hand, a high-capacity battery is assumed that 96 single cells with a capacity of 400 mAh and 5 mΩ are connected in series and charged to a charge amount of 50%. When discharging is performed with such an electric double layer capacitor and a high capacity battery connected in parallel, in the case of a discharge of 10 sec or less, it is larger that the electric double layer capacitor is connected in parallel with the high capacity battery than the high output battery. The output can be taken out. However, when comparing the output density per unit volume of the electric double layer capacitor and the high output battery, the high output battery is superior to the electric double layer capacitor. An electric double layer capacitor having the same conditions as a high-power battery has a required volume of 44.8 liters at the current technical level, and is too large to be mounted on a vehicle. In addition, there is a nano-gate capacitor that uses a new material for the electrode material, but the power density is estimated to be four times that of the electric double layer capacitor even if the maximum is estimated, and the required volume is estimated to be 11.2 liters. The On the other hand, the high-power battery under development that is also used in the present invention is estimated to be 5.3 liters. From this estimation, we believe that at present, the technology of paralleling the high-power battery and the high-capacity battery is superior to the technology of applying the electric double layer capacitor instead of the high-power battery.

  On the other hand, a problem in a battery system in which batteries having the same open-circuit voltage characteristics with respect to the state of charge SOC are arranged in parallel is expected to be a decrease in output after discharge and a decrease in input after charge. Since a large amount of electric power comes out from the high-power battery after discharging, the state of charge SOC of the high-power battery becomes lower than the state of charge SOC of the high-capacity battery, and the output characteristics of the battery system deteriorate. However, since the state of charge SOC of each battery becomes equal after discharging, the output characteristics recover over time. Since a large amount of electric power enters the high-power battery after charging, the charge state SOC of the high-power battery becomes higher than the charge state SOC of the high-capacity battery, and the input characteristics of the battery system deteriorate. However, since the state of charge SOC of each battery becomes equal after charging, the input characteristics also recover over time. Thus, if either the output characteristic recovery time or the input characteristic recovery time is too long, when the battery system is applied to a vehicle, the battery system must be composed of more batteries. This is a problem in terms of the small size and light weight required for mounting on.

  Therefore, the present invention proposes a method for optimizing and optimizing both of these recovery times, and the method is configured as follows.

  In order to achieve the above object, a method for recovering the state of charge of a battery system according to the present invention includes a high output battery having a small internal resistance and a small capacity, an internal resistance larger than that of the high output battery, and the A charge state balance recovery method for a battery system in which a high-capacity battery having a capacity larger than that of a high-power battery is connected in parallel, wherein the state of charge (SOC) -open between the high-power battery and the high-capacity battery is The state of charge of the high-power battery and the high-capacity battery is quickly recovered by an appropriate combination of circuit voltage] characteristics.

  Furthermore, the method for recovering the state of charge of the battery system according to the present invention for achieving the above object includes a high-power battery having a small internal resistance and a small capacity, and a larger internal resistance than the high-power battery. And a high-capacity battery having a large capacity and a battery system charge state balance recovery method connected in parallel, the step of supplying current from the battery system to the load, and after supplying current to the load, The state of charge (SOC) of the high-power battery and the high-capacity battery approaching each other to restore the charge state balance of the battery system.

  According to the method for recovering the state of charge of the battery system according to the present invention having the above-described configuration, a large power is instantaneously supplied by a high-power battery, or a large power is continuously supplied by a high-capacity battery. Even in this case, the battery system can be recovered early, and the vehicle can have sufficient power performance. In addition, the size and weight can be reduced compared to the performance of the battery system.

Next, an embodiment of a method for recovering the state of charge of a battery system according to the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 and FIG. 2 are diagrams for explaining why it is necessary to employ the charge state balance recovery method for a battery system according to the present invention. As shown in FIG. 1, assuming that the peak power required from the vehicle is P1, conventionally, a battery having a capacity sufficient to supply the peak power has been mounted. However, when the vehicle is running, the peak power is required for only a moment (for example, when the engine is started or suddenly accelerated). Usually, the power of P2 is sufficient. Therefore, if a battery system (a battery system that combines a high-power battery and a high-capacity battery) that can supply peak power P1 temporarily and can supply power P2 steadily, The size and weight of the system can be reduced.

  For this reason, the present invention employs a battery system in which a high-power battery 10 and a high-capacity battery 20 are connected in parallel as shown in FIG. Here, the high-power battery 10 is a battery having a small internal resistance R1 and a small capacity, and can supply a large current in a short time (the power of P1 in FIG. 1 can be supplied in a short time). It is a battery. The high-capacity battery 20 is a battery having an internal resistance R2 larger than the internal resistance R1 of the high-power battery 10 and a capacity larger than that of the high-power battery 10, and passing a current required for a long time. It is a battery that can be continued (the power of P2 in FIG. 1 can be supplied for a long time).

  The charge state-open circuit voltage characteristics of the high-power battery 10 are as shown in FIG. That is, it has a characteristic that the magnitude of the open circuit voltage becomes smaller as the state of charge (hereinafter referred to as SOC) becomes smaller. In the high-power battery 10 of the present embodiment, the difference between the open circuit voltage when the SOC is 75% and the open circuit voltage when the SOC is 25% is 400 mV. Further, the open circuit voltage-charge state characteristics of the high capacity battery 20 of the present embodiment are as shown in FIG. 4, but the tendency of the open circuit voltage to decrease with respect to the decrease of the SOC becomes gentler than that of the high output battery 10. Yes. That is, in the high capacity battery 20, the difference between the open circuit voltage when the SOC is 75% and the open circuit voltage when the SOC is 25% is 300 mV. Therefore, the decreasing tendency of the open circuit voltage with respect to the decrease in SOC in the high-power battery 10 is larger than the decreasing tendency of the open circuit voltage with respect to the decrease in SOC in the high capacity battery 20. As described above, by making the charge state-open circuit voltage characteristic of the high-power battery 10 different from the open circuit voltage-charge state characteristic of the high-capacity battery 20, the recovery time of the output characteristic and the recovery time of the input characteristic as the battery system. Both can be set to the optimum length, and the charge balance between the high-power battery 10 and the high-capacity battery 20 can be recovered early.

  Although not shown in the figure, the difference between the open circuit voltage when the SOC is 25% and the open circuit voltage when the SOC is 75% is the open circuit voltage-charge state characteristic of the high output battery 10. The difference between the open circuit voltage when the SOC is 25% and the open circuit voltage when the SOC is 75% is high capacity, so that the average open circuit voltage is 12% or more. Even if the average open circuit voltage of the battery 20 is 8% or more, both the output characteristic recovery time and the input characteristic recovery time of the battery system can be set to optimum lengths as described above. Thus, the charge balance between the high-power battery 10 and the high-capacity battery 20 can be recovered early.

  Here, SOC (%) is a value obtained by dividing the remaining capacity (Ah) of the battery by the full charge capacity (Ah) of the battery and multiplying by 100. It is an index that expresses what percentage of capacity it has.

  5 to 8 are diagrams showing discharge characteristics of the battery system in the present embodiment. FIG. 5 shows the process of changing the high-power battery SOC and the process of changing the high-capacity battery SOC until the battery system in the initial state of 30% OSC is discharged for about 10 seconds and starts discharging for a fixed time. The change process of the dischargeable power ratio as a battery system is shown. As shown in the figure, when the discharge is started, a large amount of electric power is supplied from the high-power battery 10 having a low internal resistance until the discharge is completed, and the SOC of the high-power battery 10 rapidly decreases. On the other hand, the SOC of the high-capacity battery 20 having an internal resistance larger than that of the high-power battery 10 is gradually lowered unlike that of the high-power battery 10. When the discharge is completed, the high-power battery 10 is charged by receiving power from the high-capacity battery 20, and the SOCs of the high-power battery 10 and the high-capacity battery 20 approach each other over time, and finally match. Looking at this as the dischargeable power ratio of the battery system, when the dischargeable power ratio of the battery system before discharge (based on the total power of the high-power battery 10 and the high-capacity battery 20) is 1.0 During discharge, the dischargeable power ratio decreases to 0.3, but finally recovers to about 0.8 after the end of discharge.

  FIG. 6 shows, as an initial state, when the SOCs of the high-power battery 10 and the high-capacity battery 20 are both 50%, the change process of the high-power battery SOC, the change process of the high-capacity battery SOC, and discharge as a battery system is possible. The process of changing the power ratio is shown. 7 shows, as an initial state, the change process of the high output battery SOC, the change process of the high capacity battery SOC, and the battery system when the SOCs of the high output battery 10 and the high capacity battery 20 are both 70%. The change process of the dischargeable power ratio is shown. Further, FIG. 8 shows, as an initial state, a change process of the high output battery SOC, a change process of the high capacity battery SOC, and a battery system when the SOCs of the high output battery 10 and the high capacity battery 20 are both 90%. The change process of the dischargeable power ratio is shown.

  As is clear from comparison of these figures, the SOC of the high-power battery 10 suddenly decreases from the start of discharge until the end of the discharge, and the high-power battery 10 occupies most of the power required for the discharge. It can be seen that after the discharge is completed, the high-capacity battery 20 supplies power to the high-power battery 10 so as to increase the SOC of the high-power battery 10 that has decreased. In addition, it can be seen that the final high-power battery SOC, the high-capacity battery SOC, the reduction state and the final size of the dischargeable power ratio depend on the sizes of the initial high-power battery SOC and the high-capacity battery SOC. .

  FIG. 9 is a diagram showing a general discharge characteristic of the battery system in the present embodiment, and FIG. 10 is a diagram showing a general charge characteristic of the battery system in the present embodiment. As shown in FIGS. 5 to 8, the dischargeable power ratio of the battery system continues to decrease during the discharge, and gradually recovers when the discharge ends. The same applies to the high-power battery SOC. The high-capacity battery SOC continues to decrease gradually during and after the discharge. When the battery system is charged by power regeneration, the high-power battery 10 having a low internal resistance is rapidly charged, and the high-capacity battery 20 having a high internal resistance is gradually charged.

  In the method for recovering the state of charge of the battery system according to the present invention, the balance between the discharge characteristics and the charge characteristics of the battery system is improved, and the volume and weight of the battery system can be reduced. The battery system used in the vehicle has a problem with the recovery rate of charge / discharge, such as how quickly it can be recovered after the end of discharge and how efficiently it can be charged after the end of discharge. Examples of parameters that affect the charge / discharge recovery rate include open circuit voltage characteristics with respect to the SOC and the ratio (internal resistance ratio) between the internal resistance R1 of the high-power battery 10 and the internal resistance R2 of the high-capacity battery 20. . In the present embodiment, the high-power battery 10 and the high-capacity battery 20 are constituted by lithium ion batteries (bipolar lithium ion secondary battery or laminate type lithium ion secondary battery). Open circuit voltage characteristics are greatly affected by the type of material used for the negative electrode. In the present embodiment, a hard carbon material having a large open circuit voltage change with respect to the SOC change is used so that the SOC can be easily detected.

  In a lithium ion battery using a hard carbon material, the ratio (internal resistance ratio) between the internal resistance R1 of the high-power battery 10 and the internal resistance R2 of the high-capacity battery 20 is charge (input) or discharge (output). FIG. 11 and FIG. 12 show how the recovery is affected. In this figure, the initial input ratio or output ratio of each SOC value is a value after 30 seconds have elapsed from the end of discharging or charging. The reason for setting 30 seconds is that in hybrid and electric vehicles, the discharge or charging is required between 30 seconds and 60 seconds for driving conditions in urban areas, suburban roads, and highways. Because there are many. In the output ratio and input ratio on the vertical axis, the SOC value immediately before discharging or charging is set to 1.

  As shown in FIG. 11, the output ratio decreases as the internal resistance ratio increases from SOC 60% to SOC 40%. That is, when the output ratio increases, it means that it takes time to recover after the discharge is completed. On the other hand, as shown in FIG. 12, the input ratio decreases as the internal resistance ratio increases from SOC 60% to SOC 40%. In other words, it means that it takes time to charge as the input ratio increases. This shows that the internal resistance ratio has to be reduced to some extent in order to speed up the recovery of charge and discharge.

  In order to reduce the internal resistance ratio, as described above, the internal resistance R2 of the high capacity battery 20 must be reduced. However, if the internal resistance R2 of the high capacity battery 20 is reduced, the capacity of the battery system is the same. In this case, there arises a problem that the volume of the high capacity battery 20 increases.

  FIG. 13 shows the relationship between the internal resistance ratio and the battery volume. As shown in the figure, as the internal resistance ratio is reduced, the volume of the required high capacity battery increases. The required volume increases because the thickness of the battery electrode must be reduced to lower the internal resistance in order to reduce the resistance, so the current collector and separator that cannot change the thickness This is because the volume occupied by increases. Taking this figure into consideration, an internal resistance ratio of 3.0 to 5.0 that reduces the battery volume is most preferable.

  As described above, when the recovery of charging and discharging is taken into consideration, the smaller the internal resistance ratio, the better. However, considering the increase in the battery volume, it is preferably about 2.0 to 10.0, more preferably 4. An internal resistance ratio of about 0 to 8.0, most preferably about 3.0 to 5.0, should be selected.

  FIG. 14 shows the relationship between the internal resistance ratio and the battery volume in consideration of the allowable recovery time. As shown in the figure, when the recovery time is 30 seconds, an internal resistance ratio of about 3.0 to 8.0 is required, but when the recovery time is 60 seconds, 2.5% An internal resistance ratio of about 10.0 can be selected.

  In a battery system in which the high-power battery 10 and the high-capacity battery 20 are connected in parallel, the output decreases after discharge due to the size of the internal resistance ratio. FIG. 15 shows the relationship between the output drop after discharge and the battery volume ratio with respect to the magnitude of the internal resistance ratio. The reason why the output decreases after discharging is that, as the internal resistance ratio increases, it takes time to equalize the difference in charge amount between the high-power battery 10 and the high-capacity battery 20 generated after discharging. Considering the required SOC recovery (recovery to 80% in 1 minute after discharge), the internal resistance ratio is preferably 8 or less. On the other hand, the smaller the internal resistance ratio, the more the output is maintained. However, since the volume of the battery increases, it is desirable that it is 2 or more from the figure.

  As described above, when the internal resistance ratio is set to an optimum value in consideration of the charge / discharge recovery rate and the volume of the battery, as shown in FIGS. Although the input ratio is slightly decreased, the input ratio is considerably increased as compared with the conventional one, and a small and lightweight battery system having excellent charge / discharge characteristics can be configured.

  As described above, a high-power battery having a small internal resistance and a small capacity and a high-capacity battery having a larger internal resistance than the high-power battery and a capacity larger than the high-power battery are connected in parallel. In the battery system, the open circuit voltage-charge state characteristics of the high-power battery and the high-capacity battery are appropriately combined, and the internal resistance ratio between the high-power battery and the high-capacity battery is set to an appropriate value. By setting to, the charge / discharge characteristics between the high-power battery and the high-capacity battery are improved, and the state of charge balance between the high-power battery and the high-capacity battery can be recovered early. Specifically, a high-power battery is used in which the difference between the open circuit voltage when the SOC is 75% and the open circuit voltage when the SOC is 25% is 400 mV. The difference between the open circuit voltage when the SOC is 75% and the open circuit voltage when the SOC is 25% is 300 mv. Alternatively, a high output battery having a difference between the open circuit voltage when the SOC is 25% and the open circuit voltage when the SOC is 75% is 12% or more of the average open circuit voltage of the high output battery is used. The difference between the open circuit voltage when the SOC is 25% and the open circuit voltage when the SOC is 75% is 8% or more of the average open circuit voltage of the high capacity battery 20 is used. The ratio between the internal resistance value R2 of the high capacity battery and the internal resistance value R1 of the high output battery (internal resistance ratio R2 / R1) is 2.0 to 10.0 so that the battery volume of the battery system is small. Preferably, the internal resistance ratio R2 / R1 is between 4.0 and 8.0 so that the state of charge balance can be recovered early and the battery volume of the battery system is reduced. Set.

If the method of the present invention is applied to a battery system in which such a high-power battery and a high-capacity battery are combined, it can sufficiently cope with the instantaneous high load requirement and the repeated supply of a continuous load. In addition, the size and weight can be reduced.
(Embodiment 2)
Next, an embodiment in the case where the method for recovering the state of charge of a battery system according to the present invention is applied to engine start of a vehicle will be described. FIG. 18 is a schematic configuration diagram of a hybrid vehicle system showing an application example of the present invention.

An embodiment in the case where the present invention is applied to a hybrid vehicle will be described with reference to FIG. In addition, this invention is not limited to a hybrid vehicle, It can apply to various apparatuses other than an electric vehicle including a general electric vehicle.
In FIG. 18, a thick solid line indicates a transmission path of mechanical force, and a thick broken line indicates a power line. A thin solid line indicates a control line, and a double line indicates a hydraulic system. The power train of the vehicle includes a motor 1, an engine 2, a clutch 3, a motor 4, a continuously variable transmission 5, a speed reducer 6, a differential device 7, and drive wheels 8. The output shaft of the motor 1, the output shaft of the engine 2, and the input shaft of the clutch 3 are connected to each other, and the output shaft of the clutch 3, the output shaft of the motor 4 and the input shaft of the continuously variable transmission 5 are connected to each other. ing.

  When the clutch 3 is engaged, the engine 2 and the motor 4 serve as a vehicle propulsion source, and when the clutch 3 is released, only the motor 4 serves as a vehicle propulsion source. The driving force of the engine 2 and / or the motor 4 is transmitted to the drive wheels 8 via the continuously variable transmission 5, the speed reducer 6, and the differential device 7. The continuously variable transmission 5 is supplied with pressure oil from the hydraulic device 9, and the belt is clamped and lubricated. An oil pump (not shown) of the hydraulic device 9 is driven by a motor 30.

  The motors 1, 4 and 30 are AC machines such as a three-phase synchronous motor or a three-phase induction motor, the motor 1 is mainly used for engine starting and power generation, and the motor 4 is mainly used for vehicle propulsion and braking. The motor 30 is for driving the oil pump of the hydraulic device 9. The motors 1, 4, 30 can be DC motors as well as AC motors. In addition, when the clutch 3 is engaged, the motor 1 can be used for vehicle propulsion and braking, and the motor 4 can be used for engine starting and power generation.

  The clutch 3 is a powder clutch and can adjust the transmission torque. The clutch 3 may be a dry single plate clutch or a wet multi-plate clutch. The continuously variable transmission 5 is a continuously variable transmission such as a belt type or a toroidal type, and the gear ratio can be adjusted steplessly.

  The motors 1, 4 and 30 are driven by inverters 11, 12 and 13, respectively. In the case where a DC motor is used for the motors 1, 4 and 30, a DC / DC converter is used instead of the inverter. The inverters 11 to 13 are connected to the main battery 15 via a common DC link 14, and the DC charging power of the main battery 15 is converted into AC power and supplied to the motors 1, 4, 30. 4 to convert the AC generated power into DC power and charge the main battery 15 as a battery system. Since the inverters 11 to 13 are connected to each other via the DC link 14, the power generated by the motor during the regenerative operation can be supplied directly to the motor during the power running operation without going through the main battery 15. . In this specification, a battery and a battery are used synonymously.

  The controller 16 includes a microcomputer, its peripheral components, various actuators, etc., and the rotational speed, output and torque of the engine 2, the transmission torque of the clutch 3, the rotational speed and torque of the motors 1, 4 and 30, the continuously variable transmission 5 And the charge / discharge of the main battery 15 are controlled.

  In the hybrid vehicle configured as described above, the electric power required for the motor 1 to start the engine 2 differs depending on the displacement of the engine 2 mounted. FIG. 19 is a diagram showing the relationship between the electric power required for starting the engine and the displacement. As shown in the figure, an engine with a displacement of 2 liters requires about 7 Kw of power for the cranking time when starting in 1 second, and about 3.5 liters requires about 12 Kw of power for 5.6 liters. 17Kw of power is required. Further, if the engine is to be started in a time of about 0.5 seconds, the engine with any displacement requires power of 20 Kw or more.

  As described above, in the battery system used as the battery 15 of the present embodiment, the high output battery 10 and the high capacity battery 20 are connected in parallel. If the engine fails to start as a result of supplying a large amount of power, the engine may not be restarted until the SOC of the high-power battery 10 is restored. . FIG. 20 shows the discharge characteristics of the battery 15, but the maximum power that can be supplied by the battery 15 decreases with time as shown by the dotted line. Assuming that the electric power shown in A is discharged for T1 time to start the engine for the first time, the electric power that can be supplied for the next engine starting is the electric power shown in B. If the electric power shown in B is discharged for T2 hours, the electric power that can be supplied for the next engine start is the electric power shown in C.

  Thus, if electric power is continuously supplied when the engine is started, in the case of the battery 15 of the present embodiment, it is necessary to take a long recovery time. Therefore, in the method for recovering the state of charge of the battery system according to the present invention, the engine is started as shown in the flowchart of FIG.

  Next, the engine starting procedure will be described in detail based on the flowchart of FIG.

  First, the controller 16 detects the temperature of the engine oil (S1), and calculates the required starting power of the engine 2 (S2). The temperature of the engine oil is detected by a temperature sensor provided in the oil pan of the engine 2. Further, the required starting power is obtained by referring to a table held by the controller 16 that shows the relationship between the engine oil temperature and the required starting power. Next, the controller 16 calculates the battery power of the battery 16 (S3). The battery power can be calculated by detecting the open circuit voltage of the battery 16. This is because there is a correlation between the open circuit voltage of the battery 16 and the SOC value. Specifically, the battery power is obtained with reference to a table indicating the relationship between the open circuit voltage and the battery power.

  The controller 16 determines whether or not the calculated required starting power is smaller than the battery power (S4). If the required starting power is larger than the battery power (S4: NO), it is determined that the engine 2 cannot be started and the process is terminated. On the other hand, if the required starting power is smaller than the battery power (S4: YES), the controller 16 calculates the power recovery time (S5). The power recovery time is a time until the engine 2 can be started next when the engine 2 cannot be started when power is supplied to start the engine 2, and until the SOC of the battery 16 is recovered. Is equivalent to In FIG. 21, the time corresponds to the time interval T3 of cranking.

  After calculating the power recovery time, the controller and the rotor 16 drive the motor 1 to perform cranking and start the engine 2 (S6). If the engine 2 is started by cranking (S7: YES), the process is terminated. On the other hand, if the engine 2 cannot be started by cranking (S7: NO), the process waits for the calculated power recovery time and returns to the process of step S2 (S8).

  When the engine 2 is started as described above, the power of the battery 15 rapidly decreases as indicated by D during cranking as shown in FIG. As shown, the power is recovered to the power higher than that required for cranking, and it is repeatedly reduced as indicated by F during the second cranking. Therefore, unlike the case of continuously cranking as shown in FIG. 20, the engine can no longer be started and the number of engine starts can be increased.

  The present invention can be used in battery systems for hybrid vehicles and electric vehicles.

It is a figure for demonstrating the necessity of this invention. It is a figure for demonstrating the necessity of this invention. It is a figure which shows the open circuit voltage-charge condition characteristic of a high output battery. It is a figure which shows the open circuit voltage-charge condition characteristic of a high capacity battery. It is the figure which showed the discharge characteristic of the battery system in this Embodiment. It is the figure which showed the discharge characteristic of the battery system in this Embodiment. It is the figure which showed the discharge characteristic of the battery system in this Embodiment. It is the figure which showed the discharge characteristic of the battery system in this Embodiment. It is the figure which showed the general discharge characteristic of the battery system in this Embodiment. It is the figure which showed the general charge characteristic of the battery system in this Embodiment. It is a figure which shows the influence which the ratio of the internal resistance of a high output battery and the internal resistance of a high capacity | capacitance battery has on recovery | restoration of charge. It is a figure which shows the influence which the ratio of the internal resistance of a high output battery and the internal resistance of a high capacity battery has on the recovery | restoration of discharge. It is a figure which shows the relationship between internal resistance ratio and battery volume. It is a figure which shows the relationship between internal resistance ratio and battery volume in consideration of the allowable recovery time. It is a figure which shows the relationship between the output fall after discharge with respect to the magnitude | size of internal resistance ratio, and battery volume ratio. It is a figure which shows the difference of the output characteristic of this invention and the conventional battery system. It is a figure which shows the difference of the input characteristic of this invention and the conventional battery system. It is a schematic block diagram of the system of the hybrid vehicle which shows the example of application of this invention. It is a figure which shows the relationship between the electric power required for engine starting, and displacement. It is a figure which shows the discharge characteristic of a battery. It is a flowchart which shows the starting procedure of the engine which considered the charge condition balance recovery method which concerns on this Embodiment. It is a figure where it uses for operation | movement description of the flowchart of FIG.

Explanation of symbols

1 motor,
2 engine,
10 High power battery,
15 battery,
16 controller,
20 High capacity battery.

Claims (13)

A battery system in which a high-power battery having a small internal resistance and a small capacity and a high-capacity battery having an internal resistance larger than that of the high-power battery and having a capacity larger than that of the high-power battery are connected in parallel. The state of charge balance recovery method of
The charge state balance between the high-power battery and the high-capacity battery is restored early by an appropriate combination of the [charge state (SOC) -open circuit voltage] characteristics of the high-power battery and the high-capacity battery. A method for recovering the state of charge balance of a battery system.   In the [charge state (SOC) -open circuit voltage] characteristic of the high output battery and the high capacity battery, the tendency of the open circuit voltage to decrease with respect to the decrease in the state of charge (SOC) in the high output battery is the high capacity battery. 2. The method for recovering the state of charge of a battery system according to claim 1, wherein the method is greater than the tendency of the open circuit voltage to decrease with respect to the decrease in state of charge (SOC).   In the [charge state (SOC) -open circuit voltage] characteristic of the high output battery, the difference between the open circuit voltage when the SOC is 25% and the open circuit voltage when the SOC is 75% is 400 mV or more. 2. The state of charge (SOC) -open circuit voltage is characterized in that the difference between the open circuit voltage at SOC 25% and the open circuit voltage at SOC 75% is 300 mV or more. A method for restoring the state of charge of a battery system.   In the [charge state (SOC) -open circuit voltage] characteristic of the high power battery, the difference between the open circuit voltage when the SOC is 25% and the open circuit voltage when the SOC is 75% is the average open circuit of the high power battery. In the [charge state (SOC) -open circuit voltage] characteristic of the high capacity battery, the difference between the open circuit voltage when the SOC is 25% and the open circuit voltage when the SOC is 75% is The method of claim 1, wherein the average open circuit voltage of the high capacity battery is 8% or more.   The ratio of the internal resistance value R2 of the high-capacity battery and the internal resistance value R1 of the high-power battery (internal resistance ratio R2 / R1) is 2.0 to 10 .5 so that the battery volume of the battery system becomes small. The method of claim 1, wherein the charge state balance recovery method for the battery system according to claim 1 is set.   The ratio between the internal resistance value R2 of the high capacity battery and the internal resistance value R1 of the high power battery (internal resistance ratio R2 / R1) is such that the state of charge can be recovered early and the battery volume of the battery system 2. The method of claim 1, wherein the charge state balance recovery method of the battery system according to claim 1 is set so as to be smaller than 4.0 to 8.0.   The method of claim 1, wherein the high-capacity battery is a lithium ion secondary battery.   The method of claim 7, wherein the lithium ion secondary battery is a bipolar lithium ion secondary battery or a laminate type lithium ion secondary battery. Charge state balance recovery method for a battery system in which a high-power battery having a small internal resistance and a small capacity and a high-capacity battery having a larger internal resistance and a larger capacity than the high-power battery are connected in parallel Because
Supplying current from the battery system to a load;
After supplying current to the load, the state of charge (SOC) of the high-power battery and the high-capacity battery approaches to restore the charge state balance of the battery system;
A method for recovering the state of charge balance of a battery system, comprising: Supplying a current from the battery system to the load comprises:
Calculating the power required to start the load;
Calculating a remaining capacity from a state of charge (SOC) of the battery system;
Supplying the current to the load if the calculated remaining capacity is greater than the power required to start the load;
The method for recovering the state of charge of a battery system according to claim 9, comprising:   The method of claim 10, further comprising a step of calculating a time for restoring the state of charge of the battery system after the step of calculating the remaining capacity. . Restoring the state of charge of the battery system comprises:
The method of claim 11, further comprising the step of stopping the supply of current to the load for a time required to restore the calculated state of charge balance of the battery system after supplying current to the load. Method for recovering the state of charge of the battery system in the future.   The method of claim 10, wherein the load is a motor for a starter of a vehicle engine.

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