JP6040922B2 - Charging system - Google Patents

Description

  The present invention relates to a charging system for rapidly charging a secondary battery.

  Conventionally, a charging system that rapidly charges a secondary battery using external power is known. For example, Patent Document 1 discloses a charge / discharge system that rapidly charges a secondary battery and discharges electricity stored in the secondary battery at a high output. In order to efficiently charge and discharge at a low temperature, the charge / discharge system performs pulse charge / discharge until the temperature of the secondary battery reaches the appropriate temperature when the temperature of the secondary battery is lower than the appropriate temperature. To heat the secondary battery.

JP 2006-92901 A JP 2013-84389 A

  When a high rate discharge (large current discharge) or high rate charge (large current charge) is performed on a secondary battery for a long time, the secondary battery deteriorates at a high rate. Specifically, when such charge / discharge is performed, the resistance value of the internal resistance of the secondary battery increases due to the uneven salt concentration in the secondary battery. In addition, there are excessive discharge and excessive charge as causes of high rate deterioration.

  If rapid charging is performed when high rate deterioration has occurred due to excessive charging, high rate deterioration proceeds. On the other hand, if high-rate deterioration occurs due to excessive discharge, if rapid charging is performed, the high-rate deterioration starts to recover.

  When rapid charging is performed when high rate deterioration occurs due to excessive charging, it is effective to heat the secondary battery in order to suppress the progress of high rate deterioration. On the other hand, it is not particularly necessary to heat the secondary battery when rapid charging is performed when high rate deterioration occurs due to excessive discharge. In such a case, on the contrary, there is a possibility that the deterioration of the secondary battery proceeds.

  The charge / discharge system disclosed in Patent Document 1 uniformly heats the secondary battery regardless of whether the cause of the high rate deterioration is excessive discharge or excessive charge. Therefore, the charging / discharging system of Patent Document 1 is inefficient in that the secondary battery is heated even when high rate deterioration occurs due to excessive charging.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a charging system capable of performing efficient rapid charging in consideration of the cause of the occurrence of high rate deterioration.

  According to an aspect of the present invention, the charging system rapidly charges the secondary battery using external power. The charging system includes a heater for heating the secondary battery, and control means for controlling the quick charging and the operation of the heater. When the high-rate deterioration has occurred in the secondary battery, the control means determines whether the cause of the high-rate deterioration is due to excessive charging. When it is determined that the cause of the high rate deterioration is due to excessive charge, the control means rapidly charges the secondary battery with heating by the heater. When it is determined that the cause of the high rate deterioration is not due to excessive charging, the control means rapidly charges the secondary battery without heating by the heater.

  Thus, the charging system quickly charges the secondary battery while the secondary battery is heated when the cause of the high rate deterioration is due to excessive charging, while the cause of the high rate deterioration is not due to excessive charging. When the battery is not present (that is, when the cause of high rate deterioration is excessive discharge), the secondary battery is rapidly charged without heating. That is, in the charging system, the secondary battery is not heated when the cause of the high rate deterioration is excessive discharge. Therefore, according to the charging system, efficient rapid charging can be performed in consideration of the cause of the high rate deterioration.

  According to the present invention, it is possible to perform efficient rapid charging in consideration of the cause of high rate deterioration.

1 is a diagram for explaining a charging system 10 mounted on a vehicle 1. FIG. 4 is a flowchart showing an outline of processing executed in charging system 10. It is a figure showing the relationship between the cumulative discharge amount at the time of performing the electricity supply test which produces high-rate deterioration, and the increase rate of the resistance value of charging resistance. It is the figure which put together the result of each electricity supply test (1)-(4) shown in FIG. It is a flowchart showing the detail of step S4 in FIG. The relationship between the increase rate of the resistance value of the internal resistance of the secondary battery 120 and the pressure generated by the central portion 121C of the battery cell 121 with respect to the number of cycles in the case of conducting an energization test that causes high rate deterioration due to excessive charge is shown. FIG. It is a figure showing the relationship between the position in the side surface 121S of the battery cell 121 in case the high rate deterioration has arisen by excessive charge, and a pressure.

  Hereinafter, the charging system according to each embodiment of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<A. Overview of system configuration and processing in the system>
FIG. 1 is a diagram for explaining a charging system 10 mounted on a vehicle 1. Referring to FIG. 1, when fast charging (high rate charging) is performed, vehicle 1 is connected to quick charger 8 by charging cable 9. The vehicle 1 includes a charging system 10, a motor 20, a switch 21, and an inlet 30 to which the charging cable 9 is connected.

  Charging system 10 includes a control device 110, a secondary battery 120, a plurality of temperature sensors 130, a pressure sensor 140, a plurality of heaters 150, a switch circuit 160, and a switch circuit 170. The control device 110 includes a temperature determination unit 111, a heater control unit 112, a deterioration determination unit 113, and a charge control unit 114.

  The secondary battery 120 is a battery stack (assembled battery). The electricity stored in the secondary battery 120 is sent to the motor 20. The switch 21 switches whether or not the electricity stored in the secondary battery 120 is sent to the motor. The operation of the switch 21 is controlled by an arithmetic device (not shown).

  Specifically, the secondary battery 120 includes a plurality of battery cells 121 arranged in a line along the X axis illustrated for convenience of explanation, and a fixing member 122. Each of the plurality of battery cells 121 is fixed by the fixing member 122 while being in contact with the adjacent battery cell 121. Each of the plurality of battery cells 121 has a positive electrode terminal 123 and a negative electrode terminal 124. In the secondary battery 120, a plurality of battery cells 121 are connected in series by a positive electrode terminal 123 and a negative electrode terminal 124.

  Hereinafter, two surfaces facing each other having the largest surface area among the plurality of surfaces of the battery cell 121 are referred to as “side surfaces 121S”. In addition, the central region on the side surface 121S is referred to as “central portion 121C”. Further, an end region on the side surface 121S is referred to as an “end portion 121E”. The end 121E is a region closer to the positive terminal 123 or the negative terminal 124 than the center 121C. In FIG. 1, the Z coordinate values of the central portion 121C and the two end portions 121E are the same.

  Each of the plurality of temperature sensors 130 is installed on the surface of the battery cell 121. The plurality of temperature sensors 130 measure the temperature of the battery cell 121 in which each is installed. As each temperature sensor 130, for example, a thermocouple can be used. Each temperature sensor 130 notifies the temperature determination unit 111 of the control device 110 of the measurement result.

  In addition, the installation position of each temperature sensor 130 is not specifically limited. For example, the temperature sensor 130 can be installed on the upper surface, the side surface 121S, or the surface (side surface) other than the side surface 121S in the battery cell 121.

  The pressure sensor 140 is disposed between two central battery cells 121 among the plurality of battery cells 121 arranged in a line. In the present embodiment, as an example, the pressure sensor 140 is installed between the third battery cell 121 from the left and the fourth battery cell 121 from the left. That is, the pressure sensor 140 is installed in contact with the right side surface 121S of the third battery cell 121 from the left and the left side surface 121S of the fourth battery cell 121 from the left. The pressure sensor 140 measures the pressure generated by the side surface 121S of the two battery cells 121. Specifically, the pressure sensor 140 measures pressure applied to a plurality of regions of the pressure sensor 140 (that is, pressure distribution). The pressure sensor 140 notifies the measurement result (pressure distribution) to the deterioration determination unit 113 of the control device 110. Since pressure sensor 140 is a known sensor, detailed description thereof will not be given here. It can be said that the pressure distribution is a load distribution due to a load applied to the pressure sensor 140.

  Each of the plurality of heaters 150 is installed in the vicinity of the secondary battery 120 or at a position in contact with the secondary battery 120. As an example, each heater 150 is installed on the lower surface side of battery cell 121 (the side opposite to positive electrode terminal 123 and negative electrode terminal 124). Each heater 150 heats the battery cell 121 placed at a corresponding position.

  In addition, the installation position of each heater 150 is not limited to the lower side surface of the battery cell 121, and may be a side surface side other than the side surface 121S of the battery cell 121, for example. Further, the number of heaters is not limited to two, and may be one or three or more.

  The switch circuit 160 is provided for switching whether to supply external power from the quick charger 8 to the secondary battery 120. When a predetermined signal is input from the charging control unit 114, the switch circuit 160 supplies external power to the secondary battery 120 from a state where the external power is not supplied to the secondary battery 120 (off state, cutoff state). Transitions to the ON state (ON state, conductive state).

  The switch circuit 170 is provided for switching whether or not the external power from the quick charger 8 is supplied to each heater 150. When a predetermined signal is input from the heater control unit 112, the switch circuit 170 supplies external power to the secondary battery 120 from a state where the external power is not supplied to the secondary battery 120 (off state, cutoff state). Transitions to the ON state (ON state, conductive state).

  Next, processing of the control device 110 and each functional block included will be described. The control device 110 controls the quick charging of the secondary battery 120 and the operation of each heater 150.

  The temperature determination unit 111 determines the temperature of the secondary battery 120 based on each measurement result (temperature information) acquired from the plurality of temperature sensors 130. For example, the temperature determination unit 111 sets the average value of the measurement results acquired from the plurality of temperature sensors 130 as the temperature of the secondary battery 120. The temperature determination unit 111 notifies the heater control unit 112 of the temperature of the secondary battery 120.

  The deterioration determination unit 113 determines whether high-rate deterioration has occurred in the secondary battery 120 based on the measurement result (pressure distribution) acquired from the pressure sensor 140. Further, when the high rate deterioration has occurred, the deterioration determination unit 113 determines whether the high rate deterioration is due to excessive charge or excessive discharge. The deterioration determination unit 113 notifies the heater control unit 112 of the determination result. In addition, the deterioration determination unit 113 notifies the charge control unit 114 that the determination process has been completed. Details of the determination by the deterioration determination unit 113 will be described later.

  The heater control unit 112 controls the operation of the heater 150. Specifically, the heater control unit 112 controls the operation (ON or OFF) of the switch circuit 170 based on the determination result by the deterioration determination unit 113 and the determination result by the temperature determination unit 111.

  More specifically, when high rate deterioration occurs due to excessive charging, the heater control unit 112 supplies each heater 150 with two until the temperature of the secondary battery 120 reaches a predetermined threshold (for example, 60 ° C.). The secondary battery 120 is heated. Specifically, the heater control unit 112 turns on the switch circuit 170. Note that the heater control unit 112 does not cause the heaters 150 to heat the secondary batteries 120 when high rate deterioration has occurred due to excessive discharge or when high rate deterioration has not occurred. Specifically, the heater control unit 112 keeps the switch circuit 170 in an off state (default state).

  The charging control unit 114 receives a quick charging start instruction by a user operation, and starts quick charging to the secondary battery 120 based on the completion of the deterioration determination by the deterioration determination unit 113. Specifically, the charging control unit 114 turns on the switch circuit 160 in order to rapidly charge the secondary battery 120.

  As described above, the charging system 10 mounted on the vehicle 1 rapidly charges the secondary battery 120 while being heated by each heater 150 when the cause of the high rate deterioration is due to excessive charging. When the cause of the high rate deterioration is excessive discharge, the secondary battery 120 is rapidly charged without being heated by each heater 150. That is, in the charging system 10, the secondary battery 120 is not heated when the cause of the high rate deterioration is excessive discharge. Therefore, according to the charging system 10, it is possible to perform efficient rapid charging in consideration of the cause of the high rate deterioration. In addition, according to the charging system 10, since the secondary battery 120 is not heated when high-rate deterioration has occurred due to excessive discharge, deterioration of the secondary battery due to heating can be suppressed.

<B. Details of Processing in Charging System 10>
Below, the control structure in the charging system 10 is demonstrated (FIG. 2, FIG. 5). Further, the basis of the threshold value related to the temperature defined in the control structure and the technical basis for the determination of the high rate deterioration will be described (FIGS. 3, 4, 6, and 7).

(B1. Outline of control structure)
FIG. 2 is a flowchart showing an outline of processing executed in the charging system 10. Referring to FIG. 2, in step S <b> 2, control device 110 (a processor not shown in detail) of charging system 10 determines whether or not a quick charging start instruction by a user operation has been received. When control device 110 determines that a start instruction has been received (YES in step S2), in step S4, control device 110 determines whether or not high-rate deterioration has occurred, and if high-rate deterioration has occurred, high-rate deterioration has occurred. Identify the cause. When control device 110 determines that a start instruction has not been received (NO in step S2), the process returns to step S2.

  As a result of the processing in step S4, control device 110 proceeds to step S8 when it is determined that high-rate deterioration has occurred, and performs processing when it is determined that high-rate deterioration has not occurred. The process proceeds to S24 (step S6). Furthermore, when it is determined that high-rate deterioration has occurred, control device 110 proceeds to step S10 if the cause of the high-rate deterioration is excessive charging as a result of the process in step S4, and the high-rate deterioration If the cause of occurrence is not excessive charging (ie, excessive discharging), the process proceeds to step S24 (step S8).

  In step S <b> 24, control device 110 starts quick charging of secondary battery 120. After step S24, control device 110 advances the process to step S20. In step S <b> 10, control device 110 starts quick charging of secondary battery 120. In step S <b> 12 after step S <b> 10, control device 110 starts heating of secondary battery 120 by each heater 150.

  In step S <b> 14, control device 110 determines whether or not a quick charge end instruction by a user operation has been received. When control device 110 determines that an end instruction has been received (YES in step S14), the process proceeds to step S22. When it is determined that the end instruction has not been received (NO in step S14), control device 110 determines in step S16 whether the temperature of secondary battery 120 is 60 ° C. or higher.

  When it is determined that the temperature of secondary battery 120 is 60 ° C. or higher (YES in step S16), control device 110 stops heating of secondary battery 120 by each heater 150 in step S18. When it is determined that the temperature of secondary battery 120 is lower than 60 ° C. (NO in step S16), control device 110 returns the process to step S14.

  After step S18, control device 110 determines in step S20 whether an instruction to end quick charging by a user operation has been received. Control device 110 returns the process to step S20 when it is determined that an end instruction has not been received (NO in step S20). If it is determined that an end instruction has been received (YES in step S20), control device 110 ends the quick charge in step S22. Thus, a series of quick charging processes is completed.

  Note that the order of the process shown in step S10 and the process shown in step S12 may be switched. That is, the control device 110 may start rapid charging after the heaters 150 start heating. Or control device 110 may perform both processing of Step S10 and Step S12 simultaneously.

  Further, a step of determining whether or not the temperature of the secondary battery 120 has become equal to or lower than a predetermined value (for example, 40 ° C. lower than 60 ° C.) is inserted between Step 18 and Step S20. The control device 110 may be configured to reheat the secondary battery 120 when the temperature becomes lower than a predetermined temperature. Alternatively, the control device 110 may be configured so that the secondary battery 120 is not rapidly charged until the temperature of the secondary battery 120 reaches 60 ° C.

(B2. Threshold value related to temperature)
In the above description, the configuration in which the secondary battery 120 is heated until the temperature of the secondary battery 120 reaches 60 ° C. has been described as an example. Hereinafter, the reason why the temperature of the secondary battery 120 is heated to 60 ° C. (that is, the basis of the threshold value) will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a graph showing the relationship between the cumulative discharge amount and the rate of increase in the resistance value of the charging resistance when conducting an energization test in which high-rate deterioration occurs. Specifically, FIG. 3 shows an increase rate of the resistance value of the charging resistance when a current of 240 A (ampere) is passed when the state of charge (SOC) is 50% under the condition of 25 ° C. It is the figure which represented in relation with the accumulated discharge amount.

  Referring to FIG. 3, when the temperature of secondary battery 120 is 0 ° C. (energization test (1)), the increase rate of the resistance value becomes 100% when the cumulative discharge amount becomes P1. When the temperature of the secondary battery 120 is 25 ° C. (energization test (2)), the increasing rate of the resistance value is 63% when the cumulative discharge amount becomes P2 (P2> P1). When the temperature of the secondary battery 120 is 40 ° C. (energization test (3)), the increase rate of the resistance value is 31% when the cumulative discharge amount becomes P3 (P3> P2). When the temperature of the secondary battery 120 is 60 ° C. (energization test (4)), the increase rate of the resistance value becomes 11% when the cumulative discharge amount becomes P4 (P4> P3). P1 is about 6500 Ah, P2 is about 6600 Ah, P3 is about 6650 Ah, and P4 is about 6800 Ah. Thus, as the temperature of the secondary battery 120 increases, the increasing rate of the resistance value of the internal resistance of the secondary battery 120 decreases.

  FIG. 4 is a table summarizing the results of the energization tests (1) to (4) shown in FIG. Referring to FIG. 4, based on the increase rate of the resistance value of the four energization tests (1) to (4), the increase rate of the resistance value in the energization test (1) and the energization test (2) is 50%. As it is clear from the above, it is quite high. Moreover, the increase rate of the resistance value in the current test (3) is about 30%. Furthermore, the increasing rate of the resistance value in the energization test (4) is only 10%. Therefore, based on the results of the four current tests (1) to (4), the temperature of the secondary battery 120 is preferably 40 ° C. or higher. Preferably, the temperature of the secondary battery 120 is increased to 60 ° C. Therefore, in this embodiment, for example, as shown in step S16 of FIG. 2, the reference temperature (threshold value) for heating the secondary battery 120 is set to 60 ° C.

(B3. Details of processing included in control structure)
FIG. 5 is a flowchart showing details of step S4 in FIG. Referring to FIG. 5, in step S <b> 402, control device 110 (more precisely, the processor of control device 110) acquires a measurement result (pressure distribution) sent from pressure sensor 140. In step S <b> 404, the control device 110 is generated by the average value L <b> 1 of the pressure generated by the central portion 121 </ b> C of the battery cell 121 in contact with the pressure sensor 140 and the end portion 121 </ b> E of the battery cell 121 in contact with the pressure sensor 140. An average pressure value L2 is calculated.

  In step S406, control device 110 determines whether average value L2 is larger than average value L1. When control device 110 determines that average value L2 is greater than average value L1 (YES in step S406), high rate deterioration has occurred in step S408, and the cause of the high rate deterioration is due to excessive charging. Judge that there is. When controller 110 determines that average value L2 is not greater than average value L1 (NO in step S406), it determines in step S410 whether average value L1 is greater than average value L2.

  When control device 110 determines that average value L1 is larger than average value L2 (YES in step S410), high-rate deterioration has occurred in step S412, and the cause of the high-rate deterioration is due to excessive discharge. Judge that there is. When control device 110 determines that average value L1 is not greater than average value L2 (NO in step S410), control device 110 proceeds to step S414 and determines that no high-rate deterioration has occurred. Thereby, the control apparatus 110 complete | finishes a series of processes.

(B4. Technical basis for determining high-rate degradation)
In the following, the technical basis for the determination of the high rate deterioration described with reference to FIG. 5 will be described.

  FIG. 6 shows the increase rate of the resistance value of the internal resistance of the secondary battery 120 and the pressure generated by the central portion 121C of the battery cell 121 with respect to the number of cycles in the case of conducting an energization test in which high rate deterioration due to excessive charge occurs. It is a figure showing the relationship.

  Referring to FIG. 6, the solid line represents the transition of the increase rate (%) of the resistance value of the internal resistance of battery cell 121. A broken line represents a change in pressure generated by the central portion 121C of the battery cell 121.

  As is clear from the relationship between the solid line and the broken line, there is a correlation between the pressure change caused by the central portion 121C and the increasing rate of the resistance value of the internal resistance of the secondary battery 120. Specifically, the increase rate of the resistance value of the internal resistance of the secondary battery 120 increases as the pressure generated by the central portion 121C decreases. Further, as the pressure generated by the central portion 121C increases, the increase rate of the resistance value decreases.

  FIG. 7 is a diagram illustrating the relationship between the position and the pressure on the side surface 121S of the battery cell 121 when high rate deterioration occurs due to excessive charging. Referring to FIG. 7, when high rate deterioration occurs due to excessive charging, the pressure generated by center portion 121C is smaller than the pressure generated by each end portion 121E. Specifically, the pressure generated by the central portion 121C is the smallest, and the pressure increases as the distance from the central portion 121C increases. This is because the salt concentration of the electrolyte solution in the central part inside the battery cell 121 is higher than the salt concentration of the electrolyte solution in the peripheral part.

  Therefore, by performing the determination process described with reference to FIG. 5, it is possible to determine the presence or absence of high-rate deterioration and the cause of the high-rate deterioration when high-rate deterioration occurs.

  The embodiment disclosed this time is an exemplification, and the present invention is not limited to the above contents. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Vehicle, 8 Quick charger, 9 Charging cable, 10 Charging system, 20 Motor, 21 Switch, 30 inlet, 110 Control apparatus, 111 Temperature determination part, 112 Heater control part, 113 Degradation determination part, 114 Charge control part, 120 Secondary battery, 121 battery cell, 121C central part, 121E end, 121S surface, 122 fixing member, 123 positive terminal, 124 negative terminal, 130 temperature sensor, 140 pressure sensor, 150 heater, 160, 170 switch circuit.

Claims (1)

A charging system for rapidly charging a secondary battery using external power,
A heater for heating the secondary battery;
Control means for controlling the quick charging and the operation of the heater,
The control means includes
When high-rate deterioration has occurred in the secondary battery, it is determined whether the cause of the high-rate deterioration is due to excessive charging,
When it is determined that the cause of the high-rate deterioration is due to excessive charging, the secondary battery is rapidly charged with heating by the heater,
A charging system that rapidly charges the secondary battery without heating by the heater when it is determined that the cause of the high rate deterioration is not due to excessive charging.

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