JP2013084389A - Heating system of power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: a storage device has the tendency of making progress in deterioration depending on a temperature and a charge discharge rate of the storage device.SOLUTION: A heating system comprises a heater, a current sensor, a temperature sensor, and a controller. The heater applies heat to a power storage device which performs electrical charging and discharging. The current sensor detects current value while charging/discharging the power storage device and outputs the detection result to the controller. The temperature sensor detects a temperature of the power storage device and outputs the detection result to the controller. The controller controls heating of the power storage device by use of heat of the heater. The controller heats the power storage device when the detection temperature detected by the temperature sensor is 35°C or lower, and a charge discharge rate detected by the current sensor is more than 8C.

Description

  The present invention relates to a system for heating a power storage device.

  When the secondary battery is in a low temperature state, there is a technique for warming the secondary battery using a heater in order to ensure the input / output characteristics of the secondary battery. Patent Document 1 describes a technique for heating a secondary battery when the state of charge (SOC) of the secondary battery is lower than a threshold value in order to suppress deterioration of the secondary battery.

JP 2007-330008 A

  The secondary battery may be deteriorated not only by the SOC but also by other factors. According to this inventor, it turned out that a secondary battery will deteriorate according to the relationship between the temperature of a secondary battery, and a charging / discharging rate. That is, it has been found that even when the charge / discharge rate is the same, the deterioration state of the secondary battery greatly changes depending on the temperature of the secondary battery being different.

  The heating system according to the first invention of the present application includes a heater, a current sensor, a temperature sensor, and a controller. The heater applies heat to the power storage device that performs charging and discharging. The current sensor detects a current value at the time of charging / discharging the power storage device, and outputs a detection result to the controller. The temperature sensor detects the temperature of the power storage device and outputs the detection result to the controller. The controller controls heating of the power storage device using the heat of the heater. The controller heats the power storage device when the temperature detected by the temperature sensor is 35 ° C. or lower and the charge / discharge rate acquired from the current sensor is higher than 8C.

  According to the first invention of the present application, it is possible to suppress deterioration of the power storage device that occurs due to the relationship between the temperature of the power storage device and the charge / discharge rate. It was found that when the temperature detected by the temperature sensor (temperature of the power storage device) is 35 ° C. or lower and the charge / discharge rate is higher than 8C, the deterioration of the power storage device is likely to proceed. Here, if the temperature of the power storage device is increased using the heat of the heater, it is possible to suppress the deterioration of the power storage device.

  When the charge / discharge current changes, a rate obtained from the average value of the charge / discharge current values within a predetermined period can be set as the charge / discharge rate. The predetermined period can be set as appropriate in consideration of deterioration of the power storage device due to continuous charge / discharge at a charge / discharge rate higher than 8C. When the charge / discharge current does not change, the charge / discharge rate is determined based on this current value.

  The power storage device can be mounted on a vehicle and can output energy used for traveling of the vehicle. As described above, by suppressing the deterioration of the power storage device, the travel distance of the vehicle using the output of the power storage device can be extended. When the power storage device is mounted on a vehicle, for example, an assembled battery including a plurality of single cells can be used as the power storage device. As the power storage device, for example, a lithium ion secondary battery can be used.

  A second invention of the present application is a control method for controlling heating of a power storage device that performs charging and discharging using heat of a heater, wherein the temperature of the power storage device is 35 ° C. or less, and the power storage device is charged and discharged When the charge / discharge rate is higher than 8C, the power storage device is heated. According to the second invention of the present application, the same effect as that of the first invention of the present application can be obtained.

It is the schematic which shows the structure of the battery system which is 1st Embodiment. It is a flowchart explaining the heat processing of an assembled battery. In Examples 1-5, it is a figure which shows the change of resistance increase rate. In Examples 1-5, it is a figure which shows the change of a capacity | capacitance maintenance factor.

Hereinafter, embodiments of the present invention will be described.
(First embodiment)

  The battery system which is this embodiment is demonstrated using FIG. FIG. 1 is a schematic diagram showing a configuration of a battery system. The battery system of this embodiment is mounted on a vehicle. Vehicles include hybrid cars and electric cars. The hybrid vehicle includes a fuel cell or an engine as a power source for running the vehicle, in addition to the assembled battery described later. The electric vehicle includes only an assembled battery, which will be described later, as a power source for running the vehicle.

  The assembled battery 10 includes a plurality of single cells 11 that are electrically connected in series. As the cell 11, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. An electric double layer capacitor (capacitor) can be used instead of the secondary battery. The number of unit cells 11 constituting the assembled battery 10 can be appropriately set in consideration of the required output of the assembled battery 10 and the like. In the present embodiment, all the unit cells 11 constituting the assembled battery 10 are electrically connected in series. However, the assembled battery 10 includes a plurality of unit cells 11 electrically connected in parallel. May be.

  The current sensor 21 detects the value of the current flowing through the assembled battery 10 when the assembled battery 10 is charged and discharged, and outputs the detection result to the controller 30. Here, the current value when the assembled battery 10 is discharged can be a positive value, and the current value when the assembled battery 10 is charged can be a negative value.

  The temperature sensor 22 detects the temperature of the assembled battery 10 and outputs the detection result to the controller 30. The temperature sensor 22 can be provided at one place with respect to the assembled battery 10 or at a plurality of places.

  When a plurality of temperature sensors 22 are used, the temperature of the assembled battery 10 can be specified in consideration of the outputs of these temperature sensors 22. For example, when the temperatures detected by the plurality of temperature sensors 22 are different from each other, the maximum value or the minimum value can be set as the temperature of the assembled battery 10.

  The heater 23 generates heat in response to a control signal from the controller 30. Specifically, the controller 30 can cause the heater 23 to generate heat by energizing the heater 23. The heat generated by the heater 23 is transmitted to the assembled battery 10 and can warm the assembled battery 10. The heater 23 can be provided at one place or a plurality of places with respect to the assembled battery 10.

  The controller 30 has a built-in memory 30a. The memory 30a stores a program for operating the controller 30 and various types of information. The memory 30a can also be arranged outside the controller 30.

  The assembled battery 10 is connected to the inverter 31 via system main relays SMR-B, SMR-G, and SMR-P. System main relay SMR-B is provided on a line connecting positive electrode terminal of battery pack 10 and inverter 31. System main relay SMR-G is provided on a line connecting negative electrode terminal of battery pack 10 and inverter 31.

  System main relay SMR-P and current limiting resistor 24 are electrically connected in series and electrically connected in parallel to system main relay SMR-G. The current limiting resistor 24 is used for suppressing an inrush current from flowing through the load. System main relays SMR-B, SMR-G, and SMR-P are switched between ON and OFF in response to a control signal from controller 30.

  When connecting the assembled battery 10 to the inverter 31, the controller 30 first turns on the system main relays SMR-B and SMR-P. At this time, the system main relay SMR-G remains off. Thereby, the charging / discharging current of the assembled battery 10 flows through the current limiting resistor 24. Next, after turning on the system main relay SMR-G, the controller 30 switches the system main relay SMR-P from on to off. Thereby, the connection of the assembled battery 10 and the inverter 31 is completed.

  The controller 30 can cut off the connection between the assembled battery 10 and the inverter 31 by switching the system main relays SMR-B and SMR-G from on to off.

  The inverter 31 converts the DC power output from the assembled battery 10 into AC power and outputs the AC power to the motor / generator 32. The inverter 31 converts AC power output from the motor / generator 32 into DC power and outputs the DC power to the assembled battery 10. A booster circuit can be arranged between the assembled battery 10 and the inverter 31. The booster circuit boosts the output voltage of the assembled battery 10 and outputs the boosted power to the inverter 31. The booster circuit can step down the output voltage of the inverter 31 and output the stepped down power to the assembled battery 10.

  The motor / generator 32 receives the electric power output from the inverter 31 and generates kinetic energy for running the vehicle. The motor / generator 32 is connected to wheels, and the kinetic energy generated by the motor / generator 32 is transmitted to the wheels. When the vehicle is stopped or decelerated, the motor / generator 32 converts kinetic energy generated during braking of the vehicle into electrical energy (AC power). The AC power generated by the motor / generator 32 is output to the inverter 31.

  Next, the heat treatment in the battery system of this embodiment will be described with reference to the flowchart shown in FIG. The process shown in FIG. 2 is executed by the controller 30 and is performed at a predetermined cycle. As the predetermined cycle, for example, a cycle of 30 minutes can be used.

  In step S <b> 101, the controller 30 acquires a current value at the time of charging / discharging the assembled battery 10 based on the output of the current sensor 21. The controller 30 continuously acquires the current value using the current sensor 21 during a predetermined period. When the battery pack 10 is discharged, the current value is a positive value, and when the battery pack 10 is charged, the current value is a negative value.

  In step S <b> 102, the controller 30 acquires the temperature of the assembled battery 10 based on the output of the temperature sensor 22. And the controller 30 discriminate | determines whether the temperature of the assembled battery 10 is 35 degrees C or less. Information regarding the temperature of 35 ° C. is stored in advance in the memory 30a. When the temperature of the assembled battery 10 is higher than 35 ° C., the present process is terminated. When the temperature of the assembled battery 10 is 35 ° C. or lower, the process proceeds to step S103.

  In step S103, the controller 30 determines whether or not the charge / discharge rate when the assembled battery 10 is charged / discharged is higher than 8C. That is, the controller 30 determines whether the charge rate or the discharge rate is higher than 8C. Information about the rate 8C is stored in advance in the memory 30a. The charge / discharge rate corresponds to the average value of the current values acquired in the process of step S101 during a predetermined period.

  As will be described later, when charging / discharging of the assembled battery 10 is continued at a high rate (a rate higher than 8C), the assembled battery 10 is likely to deteriorate. The predetermined period is a period for determining whether or not high-rate charging / discharging is continuously occurring. The predetermined period may be appropriately set in consideration of the progress of deterioration of the assembled battery 10 and the like. it can. For example, the predetermined period can be a period of 30 minutes or less.

  The current value detected by the current sensor 21 changes according to the traveling pattern of the vehicle. The controller 30 acquires a change in the current value during a predetermined period and calculates an average value of the current values. Then, the controller 30 can calculate the charge / discharge rate based on the average value of the current values and the capacity of the assembled battery 10. The capacity of the assembled battery 10 can be measured in advance. The controller 30 determines whether or not the calculated charge / discharge rate is higher than 8C.

  When the charge / discharge rate is lower than 8C, this process ends. When the charge / discharge rate is higher than 8C, the process proceeds to step S104. In step S <b> 104, the controller 30 drives the heater 23 to warm the assembled battery 10. By heating the assembled battery 10, the temperature of the assembled battery 10 rises. According to the processing shown in FIG. 2, when the temperature of the assembled battery 10 becomes higher than 35 ° C., the controller 30 stops driving the heater 23. To do.

  According to the present embodiment, the deterioration of the assembled battery 10 can be suppressed by performing the processing shown in FIG. Here, the experimental result which shows the deterioration state of the assembled battery 10 when changing the temperature and charging / discharging rate (average value) of the assembled battery 10 is demonstrated.

  First, as shown in Table 1 below, in Examples 1 to 5, the temperature and charge / discharge rate (average value) of the assembled battery 10 were varied. Under the conditions of temperature and charge / discharge rate (average value) shown in each of Examples 1 to 5, the resistance increase rate and the capacity maintenance rate of the assembled battery 10 were measured. A lithium ion secondary battery was used as the single battery 11 constituting the assembled battery 10.

  In FIG. 3, the change of the resistance increase rate in Examples 1-5 is shown. In FIG. 3, the vertical axis represents the resistance increase rate, and the horizontal axis represents the square root of the cumulative value of the discharge amount. The horizontal axis corresponds to the travel distance or travel time of the vehicle.

  The resistance increase rate is represented by a ratio (Rr / Rini) between the resistance value (Rini) of the assembled battery 10 in the initial state and the resistance value (Rr) of the assembled battery 10 in the deteriorated state. The accumulated value of the discharge amount is obtained by integrating the current value detected by the current sensor 21. Here, the discharge current can be a positive value and the charging current can be a negative value.

  The initial state is a state serving as a reference for determining deterioration of the assembled battery 10. For example, a state immediately after manufacturing the assembled battery 10 can be set as an initial state. Since the assembled battery 10 tends to deteriorate due to charging / discharging, the assembled battery 10 after charging / discharging becomes the assembled battery 10 in a deteriorated state. The resistance increase rate is an index for determining the deterioration of the assembled battery 10, and the assembled battery 10 deteriorates as the resistance increase rate increases.

  As shown in FIG. 3, in Examples 1, 2, 4, and 5, even when the square root of the cumulative value of the discharge amount increases, the resistance increase rate hardly increases. On the other hand, in Example 3, as the square root of the cumulative value of the discharge amount increases, the resistance increase rate increases.

  According to the experimental results shown in FIG. In Examples 2 and 4, the charge / discharge rate (average value) is the same, and the temperature of the assembled battery 10 is different. When Examples 2 and 4 are compared, as shown in FIG. 3, even if the square root of the cumulative value of the discharge amount increases, the resistance increase rate hardly increases. For this reason, when the charge / discharge rate (average value) is 7.2 C, even if the temperature of the assembled battery 10 is changed, the deterioration of the assembled battery 10 (an increase in the resistance increase rate) is hardly affected. Yes.

  On the other hand, in Examples 3 and 5, the charge / discharge rate (average value) is the same, and the temperature of the assembled battery 10 is different. When Examples 3 and 5 are compared, as shown in FIG. 3, in Example 3, the resistance increase rate is increased, whereas in Example 5, the resistance increase rate is difficult to increase. For this reason, when the charge / discharge rate (average value) is 8.9 C, deterioration of the assembled battery 10 (increase in resistance increase rate) can be reduced by changing the temperature of the assembled battery 10. That is, the temperature of the assembled battery 10 is increased using the heater 23 to change from the state of Example 3 to the state of Example 5, thereby suppressing deterioration of the assembled battery 10 (increase in resistance increase rate). Can do.

  In FIG. 4, the change of the capacity | capacitance maintenance factor in Examples 1-5 is shown. In FIG. 4, the vertical axis indicates the capacity maintenance rate, and the horizontal axis indicates the square root of the accumulated value of the discharge amount. The capacity maintenance rate is represented by a ratio (Cr / Cini) between the capacity (Cini) of the assembled battery 10 in the initial state and the capacity (Cr) of the assembled battery 10 in the deteriorated state.

  The initial state is a state serving as a reference for determining deterioration of the assembled battery 10. For example, a state immediately after manufacturing the assembled battery 10 can be set as an initial state. Since the assembled battery 10 tends to deteriorate due to charging / discharging, the assembled battery 10 after charging / discharging becomes the assembled battery 10 in a deteriorated state. The capacity maintenance rate is an index for determining the deterioration of the assembled battery 10, and the assembled battery 10 deteriorates as the capacity maintenance rate decreases.

  As shown in FIG. 4, in Examples 1 to 5, the capacity retention rate decreases as the square root of the cumulative value of the discharge amount increases. Here, in Example 3, compared with Examples 1, 2, 4, and 5, the capacity retention rate is greatly reduced.

  According to the experimental results shown in FIG. In Examples 3 and 5, the charge / discharge rate (average value) is the same, and the temperature of the assembled battery 10 is different. Comparing Examples 3 and 5, as shown in FIG. 4, the capacity retention rate is greatly decreased in Example 3, whereas the capacity retention rate is difficult to decrease in Example 5. .

  For this reason, when the charge / discharge rate (average value) is 8.9 C, deterioration of the assembled battery 10 (decrease in capacity maintenance rate) can be suppressed by changing the temperature of the assembled battery 10. That is, the temperature of the assembled battery 10 is increased using the heater 23 to change from the state of Example 3 to the state of Example 5, thereby suppressing deterioration of the assembled battery 10 (decrease in capacity maintenance rate). Can do.

  Table 2 below shows the slope of the resistance increase rate (change amount) and the slope of the capacity maintenance rate (change amount) in each of Examples 1 to 5 based on the experimental results shown in FIGS. Show the relationship. In Table 2, the slope of the resistance increase rate and the slope of the capacity retention rate were calculated based on the least square method.

  As shown in Table 2, when Examples 2 and 4 are compared, even when the temperature of the assembled battery 10 is changed, the resistance increase rate and the capacity maintenance rate are hardly changed. On the other hand, when Examples 3 and 5 are compared, by increasing the temperature of the assembled battery 10 by warming the assembled battery 10, it is possible to suppress the increase amount of the resistance increase rate and the decrease amount of the capacity maintenance rate. In consideration of the slope of the resistance increase rate and the slope of the capacity maintenance rate, the performance (input / output characteristics) of the assembled battery 10 is drastically reduced in Example 3 as compared with Examples 1, 2, 4, and 5. I understand that.

  In Examples 3 and 5, the charge / discharge rate (average value) is 8.9 C. However, when the charge / discharge rate is higher than 8 C, the assembled battery 10 deteriorates in relation to the temperature of the assembled battery 10. It becomes easy to do. In Example 3, the temperature of the assembled battery 10 is 25 ° C., and in Example 5, the temperature of the assembled battery 10 is 45 ° C. When the temperature of the assembled battery 10 is 35 ° C. or less, the charge / discharge rate is Therefore, the assembled battery 10 is likely to deteriorate.

  That is, when the temperature of the assembled battery 10 is 35 ° C. or lower and the charge / discharge rate is higher than 8C, the assembled battery 10 is likely to deteriorate as in the third embodiment. Therefore, as described in the process shown in FIG. 2, when the temperature of the assembled battery 10 is 35 ° C. or lower and the charge / discharge rate is higher than 8C, the assembled battery 10 is deteriorated by warming the assembled battery 10. Can be suppressed.

  When charging / discharging at high rate when the assembled battery 10 is in a low temperature state, the salt concentration distribution of the electrolytic solution tends to vary between the positive electrode and the negative electrode. When the variation in the salt concentration distribution occurs, the performance of the assembled battery 10 is degraded. The low temperature state is a state where the temperature of the assembled battery 10 is lower than 35 ° C., and the high rate is a state where the charge / discharge rate is higher than 8C.

  When a variation occurs in the salt concentration distribution of the electrolytic solution, the variation in the salt concentration distribution can be reduced by warming the assembled battery 10. For this reason, when the temperature of the assembled battery 10 is 35 ° C. or lower and the charge / discharge rate is higher than 8C, the assembled battery 10 is warmed to reduce the variation in the salt concentration distribution, thereby deteriorating the assembled battery 10. Can be suppressed.

  If the assembled battery 10 is uniformly warmed when the assembled battery 10 is in a low temperature state, the assembled battery 10 may be deteriorated depending on the charge / discharge rate. Therefore, in the present embodiment, the assembled battery 10 is heated in consideration of the relationship between the temperature of the assembled battery 10 and the charge / discharge rate. That is, the assembled battery 10 is warmed when the temperature of the assembled battery 10 is 35 ° C. or lower and the charge / discharge rate (average value) is higher than 8C. Thereby, deterioration of the assembled battery 10 when the temperature and charging / discharging rate of the assembled battery 10 have a specific relationship can be suppressed.

  In the present embodiment, the dedicated heater 23 for heating the assembled battery 10 is used, but the present invention is not limited to this. It is only necessary that the assembled battery 10 can be warmed, and the heat source can be appropriately selected. For example, when the engine is mounted on the vehicle, heat generated by the engine can be supplied to the assembled battery 10 to warm the assembled battery 10.

  Specifically, a duct for supplying heat generated in the engine to the assembled battery 10 can be provided, and a fan can be provided in the duct. When the assembled battery 10 is warmed, the engine heat can be supplied to the assembled battery 10 by driving the fan. When the battery pack 10 is not warmed, the fan drive may be stopped.

  In the present embodiment, whether or not the assembled battery 10 is to be warmed is determined based on the charge / discharge rate acquired while the vehicle is traveling, but the present invention is not limited to this.

  For example, the present invention can also be applied to a system in which power from an external power source is supplied to the assembled battery 10 to charge the assembled battery 10. The external power source is a power source arranged outside the vehicle, and an example of the external power source is a commercial power source. When power from an external power source is supplied to the assembled battery 10, it is charged with a constant current. When the external power source outputs AC power, a charger that converts AC power into DC power can be mounted on the vehicle. When the external power source outputs DC power, DC power may be supplied to the assembled battery 10.

  When the temperature of the assembled battery 10 when starting to supply power from the external power source to the assembled battery 10 is 35 ° C. or lower and the charging rate is higher than 8C, the assembled battery 10 can be warmed using the heater 23. After the assembled battery 10 has been warmed, charging of the assembled battery 10 may be started, or the assembled battery 10 may be warmed while charging the assembled battery 10.

  On the other hand, the present invention can also be applied to a system in which the power of the assembled battery 10 is supplied to an external device to operate the external device. An external device is an electronic device arranged outside the vehicle. Examples of the external device include an electrical appliance.

  When the temperature of the assembled battery 10 at the start of supplying the electric power of the assembled battery 10 to an external device is 35 ° C. or lower and the discharge rate is higher than 8C, the assembled battery 10 can be warmed using the heater 23. Discharge of the assembled battery 10 may be started after the assembled battery 10 has been warmed, or the assembled battery 10 may be warmed while discharging the assembled battery 10.

  In this embodiment, although the case where the assembled battery 10 was mounted in the vehicle was demonstrated, it does not restrict to this. The present invention can be applied to a device in which the cell 11 is mounted. Here, in order to suppress deterioration of the unit cell 11, the heat treatment described in the present embodiment (see FIG. 2) can be performed.

10: assembled battery (power storage device) 11: cell 21: current sensor 22: temperature sensor 23: heater 24: current limiting resistor 30: controller 30a: memory 31: inverter 32: motor generator

Claims (6)

A heater for applying heat to a power storage device that performs charging and discharging;
A current sensor for detecting a current value during charging and discharging of the power storage device;
A temperature sensor for detecting a temperature of the power storage device;
A controller for controlling the heating of the power storage device using the heat of the heater,
The controller heats the power storage device when the temperature detected by the temperature sensor is 35 ° C. or lower and the charge / discharge rate acquired from the current sensor is higher than 8C.   The heating system according to claim 1, wherein the charge / discharge rate is a rate obtained from an average value of charge / discharge current values within a predetermined period.   The heating system according to claim 1, wherein the power storage device outputs energy used for running the vehicle.   The heating system according to any one of claims 1 to 3, wherein the power storage device is a lithium ion secondary battery. A control method for controlling heating of a power storage device that performs charge and discharge using heat of a heater,
A control method, comprising: heating the power storage device when a temperature of the power storage device is 35 ° C. or lower and a charge / discharge rate during charge / discharge of the power storage device is higher than 8C. The control method according to claim 5, wherein the charge / discharge rate is a rate obtained from an average value of charge / discharge current values within a predetermined period.

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