JP4300363B2 - Battery pack capacity adjustment apparatus and method - Google Patents

Description

  The present invention relates to an assembled battery capacity adjustment apparatus and method.

  2. Description of the Related Art Conventionally, a technique for uniformly adjusting a charge rate between cells in order to prevent overcharge / overdischarge due to variation in charge rate between unit cells is known (see, for example, Patent Document 1). In this technique, a cell having a high charge capacity is discharged, and the charge rate is adjusted uniformly by matching the charge rate of the cell having a low charge capacity.

For such adjustment, for example, a circuit is used as shown in FIG. That is, the circuit for adjustment is composed of a reference voltage unit and a bypass circuit unit. For a cell having a high charging rate, the charging rate is increased by utilizing the fact that the open circuit voltage of the cell becomes high as shown in FIG. If the reference voltage (capacity adjustment start voltage) is high, the bypass circuit is turned on to adjust the charging rate.
JP 2003-61257 A

  However, in the prior art, since the reference voltage is constant, the internal resistance of the battery increases and the operation frequency of the bypass circuit increases when the battery is deteriorated or at a low temperature. FIG. 9 shows this state. As shown in the figure, for a deteriorated cell, the amount of energy loss increases and the vehicle fuel consumption performance deteriorates.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an assembled battery capacity adjustment device capable of reducing the amount of energy loss and improving the vehicle fuel consumption performance, and It is to provide a method.

  The battery pack capacity adjustment device of the present invention discharges a cell when one of the cells of the battery pack formed by connecting a plurality of unit cells exceeds a reference voltage. The charging rate between cells is adjusted uniformly. The assembled battery capacity adjusting device includes an internal resistance detecting unit and a charging rate control unit, the internal resistance detecting unit detects an internal resistance of the assembled battery, and the charging rate control unit detects the internal resistance detected by the internal resistance detecting unit. When the resistance is greater than or equal to the threshold value, control is performed to reduce the charging rate of the assembled battery.

  According to the present invention, the internal resistance of the assembled battery is detected, and when the internal resistance is equal to or greater than the threshold value, the target charging rate is reduced. For this reason, when the assembled battery is deteriorated, the internal resistance is reduced by reducing the charging rate. As a result, it is possible to make it difficult for the voltage of each cell to exceed the reference voltage. That is, when the assembled battery deteriorates, the voltage of each cell tends to exceed the reference voltage, but this can be suppressed and the amount of energy loss can be prevented from increasing. Accordingly, it is possible to reduce the amount of energy loss and improve the vehicle fuel consumption performance.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. In the drawings, the same or similar elements are denoted by the same reference numerals, and description thereof is omitted. Moreover, in the following description, the example which applied the assembled battery capacity adjustment apparatus which concerns on this embodiment to the battery of an electric vehicle (EV) is demonstrated.

  FIG. 1 is a hardware configuration diagram of an assembled battery capacity adjustment device according to the present embodiment. As shown in FIG. 1, the assembled battery capacity adjustment device 1 includes a vehicle system 10 and a battery control unit 20. The vehicle system 10 includes an assembled battery 11, a current sensor 12, a voltage sensor 13, a temperature sensor 14, a main relay 15, a drive motor (load) 16, and an auxiliary machine system (load) 17.

  The assembled battery 11 is formed by connecting a plurality of unit cells generally called cells in series. The assembled battery 11 is connected to the drive motor 16 and the auxiliary system 17 via the current sensor 12 and the main relay 15 and supplies DC power to the drive motor 16 and the auxiliary system 17. It has become.

  The current sensor 12 measures the current value flowing through the assembled battery 11. The voltage sensor 13 measures the potential of the assembled battery 11. The temperature sensor 14 detects the temperature of the assembled battery 11. Moreover, these sensors 12-14 transmit the information of the measured value to the battery control unit 20, respectively.

  The main relay 15 controls power supply from the assembled battery 11 and is turned on / off by a command from the battery control unit 20. The drive motor 16 operates when the main relay 15 is turned on and electric power is supplied from the assembled battery 11, and generates a driving force to drive the vehicle. The drive motor 16 supplies regenerative power to the assembled battery 11 when the vehicle is braked, and charges the assembled battery 11. The auxiliary machine system 17 is operated by the electric power from the assembled battery 11 like the drive motor 16 such as an air conditioner.

  The battery control unit 20 includes a bypass circuit unit (bypass circuit unit) 21, a reference voltage unit 22, a CPU (internal resistance detection unit, a charge rate control unit, a calculation unit) 23, a counter (counting unit) 24, and a memory 25. The charging / discharging and capacity adjustment of the assembled battery 11 are controlled.

  The bypass circuit unit 21 adjusts the charging rate between the cells uniformly by discharging the cells when any of the cells of the assembled battery 11 exceeds a reference voltage. is there. The reference voltage unit 22 generates a reference voltage and outputs it to the bypass circuit unit 21.

  The CPU 23 performs on / off control of the main relay 15. Further, the CPU 23 is configured to input measurement value information from the current sensor 12 and the voltage sensor 13 and calculate the internal resistance of the assembled battery 11. Here, the internal resistance varies depending on the temperature. For this reason, the CPU 23 is configured to input measurement value information from the temperature sensor 14 and correct the temperature for the obtained internal resistance.

  Further, the CPU 23 has a function of determining whether the internal resistance is equal to or greater than a threshold value. And CPU23 has a function which performs control which decreases the charging rate of the assembled battery 11, when internal resistance is more than a threshold value. Here, CPU23 can perform the following processes as control which reduces a charging rate. That is, for example, the CPU 23 operates the drive motor 16 and the auxiliary machine system 17 to increase the amount of electric power supplied thereto, thereby reducing the charging rate of the assembled battery 11 or by the bypass circuit unit 21. By discharging each cell, the charging rate of the assembled battery 11 can be reduced.

  The counter 24 counts the number of times that the voltage of each cell exceeds the reference voltage. The memory 25 stores various data and the like, and also stores time information when the counter 24 counts.

  Further, the CPU 23 described above has a function of obtaining a charge rate adjustment frequency from the count of the counter 24 and performing control to increase a target charge rate when the obtained frequency is lower than a predetermined value. Here, as control for increasing the charging rate, the CPU 23, for example, operates the auxiliary system 17 and the like with an auxiliary battery 50 described later as much as possible, and increases the charging rate by suppressing power consumption.

  The assembled battery capacity adjustment apparatus 1 includes an ignition switch 30, a connection switch 40, an auxiliary battery 50, and a vehicle system CPU 60 in addition to the above configuration. And when a passenger | crew turns on the ignition switch 30, the connection switch 40 will connect and the electric power from the auxiliary | assistant battery 50 will be supplied to CPU23 and vehicle system CPU60. The vehicle system CPU 60 controls the drive motor 16 and the auxiliary system 17. When the charge rate of the assembled battery 11 is decreased, the vehicle system CPU 60 receives an instruction from the CPU 23 and the auxiliary motor 16. System 17 is activated.

  Next, an outline of the operation of the assembled battery capacity adjustment device according to the present embodiment will be described. First, in the present apparatus 1, the charging rate between cells is uniformly adjusted in order to prevent variation in charging rate between cells. At this time, the assembled battery capacity adjustment device 1 according to the present embodiment adjusts the charging rate of each cell to a target charging rate. FIG. 2 is an explanatory diagram of the target charging rate, (a) shows the initial state, and (b) shows the state after adjustment.

  First, FIG. 2 shows input characteristics and output characteristics. Here, the input characteristic indicates the chargeable capacity of the assembled battery 11, and as shown in this characteristic, the chargeable capacity of the assembled battery 11 tends to decrease as the charging rate increases. Further, the output characteristics indicate the dischargeable capacity of the assembled battery 11, and as shown in this characteristic, the dischargeable capacity of the assembled battery 11 tends to increase as the charging rate increases.

  Further, FIG. 2 shows a vehicle request output and a vehicle request input. Here, the vehicle request output is the minimum discharge capacity required for vehicle operation, and the vehicle request input is a value that must be secured at least for charging. For this reason, the assembled battery 11 must always ensure the charging / discharging electric power more than a vehicle request output and a vehicle request input. And it is desirable for this charging / discharging electric power to have margin as much as possible with respect to a vehicle request output and a vehicle request input. Therefore, in the present apparatus 1, the charging rate between the cells is adjusted to the charging rate SOC1 that is the intersection of the input characteristics and the output characteristics.

  However, when the assembled battery 11 deteriorates or the temperature is low, the internal resistance increases and the frequency of adjustment also increases. Therefore, the amount of energy loss also increases. Therefore, in order to prevent this, the apparatus 1 executes the following operation.

  That is, first, the CPU 23 inputs signals from the current sensor 12 and the voltage sensor 13 to obtain the internal resistance of the assembled battery 11. Further, the CPU 23 corrects the internal resistance obtained from the signal from the temperature sensor 14. Next, the CPU 23 determines whether or not the obtained internal resistance is larger than a predetermined threshold value.

  As a result of the determination, when the obtained internal resistance is larger than the threshold value, the voltage of each cell of the assembled battery 11 is more likely to exceed the reference voltage than initially assumed. That is, the charge rate of each cell is discharged and the amount of energy loss is increased.

  Here, the internal resistance varies depending on the charging rate of the assembled battery 11, and the internal resistance decreases as the charging rate decreases. For this reason, CPU23 reduces the charging rate of the assembled battery 11 in order to reduce the amount of energy loss. Specifically, as shown in FIG. 2B, the charging rate that is the adjustment target of each cell is SOC1, but control is performed so that the charging rate is reduced to SOC2. As a result, the voltage of each cell does not easily exceed the reference voltage, and the amount of energy loss is reduced to improve vehicle fuel efficiency.

  Here, for example, as a result of reducing the charging rate of the assembled battery 11, the voltage of each cell hardly exceeds the reference voltage, and the cell potential variation eliminating function inherently possessed by the assembled battery capacity adjustment device 1 may not work. There is sex. For this reason, the counter 24 counts the number of times that the voltage of each cell exceeds the reference voltage, and the memory 25 stores time information when the voltage of each cell exceeds the reference voltage, for example.

  And CPU23 calculates | requires the adjustment frequency of a charging rate from these information, and when this frequency is less than predetermined value, it performs control which increases the charging rate of the assembled battery 11. FIG. Specifically, the charging rate is changed to the high SOC side by about 5%. As a result, the voltage of each cell easily exceeds the reference voltage, and variations in cell potential can be eliminated.

  Next, a method for adjusting the capacity of the assembled battery according to this embodiment will be described. FIG. 3 is a flowchart showing a method of adjusting the capacity of the assembled battery according to this embodiment. In the following description, a control method when deterioration of the assembled battery 11 proceeds will be described.

  First, as shown in FIG. 3, the CPU 23 obtains the internal resistance of the assembled battery 11 based on signals from the current sensor 12 and the voltage sensor 13 (ST1).

  Next, CPU23 correct | amends the calculated | required internal resistance based on the temperature information from the temperature sensor 14, and determines the deterioration degree of the assembled battery 11 (ST2). That is, the memory 25 stores information on initial internal resistance in advance, and the CPU 23 reads this information. Then, the CPU 23 determines the degree of deterioration by comparing the temperature-corrected internal resistance with the initial internal resistance stored in advance.

  Next, the CPU 23 calculates a charge rate at which input / output is possible from the degree of deterioration (ST2). Here, the charge rate that can be input / output refers to a range of charge rates in which the assembled battery 11 can be charged / discharged without any trouble in vehicle operation (hereinafter referred to as an input / output enabled range).

  FIG. 4 is an explanatory diagram of the input / output possible range of the assembled battery 11. FIG. 4 shows the input characteristics and output characteristics, as well as the vehicle required output and vehicle required input, as in FIG. 2, but the input battery characteristics and output characteristics may be different when the battery pack 11 is new or deteriorated. It is shown.

  First, as shown in FIG. 4, the assembled battery 11 is in a state in which both input characteristics and output characteristics are high when it is new. For this reason, the input / output possible range of the assembled battery 11 is relatively wide. On the other hand, when the assembled battery 11 deteriorates, the power values indicated by the input characteristics and the output characteristics become low. For this reason, the input / output possible range of the assembled battery 11 is narrower than when it is new.

  FIG. 3 will be referred to again. As described above, the input / output possible range changes depending on the deterioration degree of the assembled battery 11. For this reason, when determining the deterioration level of the assembled battery 11, the CPU 23 obtains a new input characteristic and output characteristic from the deterioration degree, and a range of the charge rate that can be input / output from the characteristic and the vehicle request output and the vehicle request input. That is, the input / output possible range is obtained (ST2).

  Thereafter, the CPU 23 determines whether or not the internal resistance obtained in step ST1 exceeds a threshold value (ST3). That is, the CPU 23 determines whether the cell voltage is likely to exceed the reference voltage. Here, the threshold value is preset by a user or the like.

  FIG. 5 is an explanatory diagram of the threshold value and shows the correlation between the amount of energy loss and the reference voltage and the correlation with the internal resistance. First, it is assumed that the energy loss amount α that the user or the like may lose to the maximum is set in advance. Further, it is assumed that the reference voltage generated by the reference voltage unit 22 of the device 1 is V1.

  In this case, as is apparent from FIG. 5, the CPU 23 can obtain the maximum value of the internal resistance from the correlation between the two. Then, the CPU 23 sets the maximum value of the internal resistance as a threshold value. Note that an appropriate value for the threshold value may be obtained in advance and stored directly in the memory 25.

  FIG. 3 will be referred to again. When it is determined that the internal resistance obtained in step ST1 does not exceed the threshold value (ST3: NO), the amount of energy loss is not particularly increased, so that adjustment is not necessary, and the process ends.

  On the other hand, when it is determined that the internal resistance obtained in step ST1 exceeds the threshold value (ST3: YES), the CPU 23 sets a target charging rate as a charging rate change target (ST4). Here, the CPU 23 sets the target charging rate within the input / output possible range obtained in step ST2. At this time, the CPU 23 sets the target charging rate so that the amount of energy loss is minimized, or appropriately reduces the charging rate so as to use the cell potential variation eliminating function as much as possible.

  Thereafter, the CPU 23 determines whether or not the discharge can be performed more than the vehicle required output at the set target charging rate (ST5). Here, if it is possible to perform discharge more than the vehicle required output (ST5: YES), the CPU 23 adjusts the charging rate with the target charging rate set in step ST4 (ST6). Thereby, it is possible to prevent the voltage of each cell from exceeding the reference voltage and increase the amount of energy loss. The CPU 23 may reduce the charging rate by discharging the bypass circuit unit 21, or transmits the charging rate information to the vehicle system CPU 60, and the driving motor 16 and the auxiliary machine system 17 are transmitted by the vehicle system CPU 60. May be controlled to decrease the charging rate.

  If it is impossible to discharge more than the vehicle required output (ST5: NO), the CPU 23 adjusts the charging rate after resetting the target charging rate (ST7). FIG. 6 is a detailed explanatory diagram of step ST7 shown in FIG. For example, if the CPU 23 sets the target charging rate SOC3 outside the input / output possible range in step ST4, there is a possibility of hindering future vehicle travel. For this reason, the CPU 23 resets the target charging rate.

  Specifically, the CPU 23 resets the target charging rate to SOC4 which is the lowest value within the input / output possible range, although the target charging rate is SOC3. This prevents adverse effects on future vehicle travel. And CPU23 will reduce a charging rate toward this target charging rate.

  Then, after steps ST6 and ST7, the process ends. Thereafter, for example, the process shown in FIG. 3 is repeated until the ignition switch 30 of the vehicle is turned off.

  Thus, according to the assembled battery capacity adjusting apparatus 1 and the method according to the present embodiment, the internal resistance of the assembled battery 11 is detected, and when the internal resistance is equal to or greater than the threshold, the target charging rate is set. Control to decrease. For this reason, when the assembled battery 11 deteriorates or the like, the internal resistance is reduced by reducing the charging rate. As a result, it is possible to make it difficult for the voltage of each cell to exceed the reference voltage. That is, when the assembled battery 11 deteriorates, the voltage of each cell tends to exceed the reference voltage, but this can be suppressed, and the amount of energy loss can be prevented from increasing. Accordingly, it is possible to reduce the amount of energy loss and improve the vehicle fuel consumption performance.

  Moreover, in the assembled battery capacity adjustment apparatus 1 according to the present embodiment, the number of times that the voltage of each cell exceeds the reference voltage is counted to obtain the adjustment rate of the charging rate, and when the frequency falls below a predetermined value Then, control for increasing the charging rate of the assembled battery 11 is performed. Thereby, the voltage of each cell can be easily exceeded the reference voltage, for example, even if the charge rate is reduced too much and the cell potential variation eliminating function is substantially disabled, The variation elimination function can be restored and the cell potential can be adjusted.

  Further, when the charging rate of the assembled battery 11 is decreased, the drive motors 16 and 17 are operated to increase the amount of power supplied from the assembled battery 11 to these parts 16 and 17. For this reason, it is possible to effectively reduce the charging rate by effectively using the drive motors 16 and 17 without adding a new configuration.

  Moreover, when reducing the charging rate of the assembled battery 11, if the detected internal resistance is equal to or greater than the threshold, the bypass circuit unit 21 discharges each cell, thereby reducing the charging rate of the assembled battery 11. Yes. For this reason, it is possible to easily reduce the charging rate by effectively using the bypass circuit unit 21 originally having a discharging function.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention. For example, in the above-described embodiment, an example in which the assembled battery capacity adjustment device and method are applied to a battery of an electric vehicle has been described. However, the present invention is not limited to this, and the present invention is not limited to this. You may make it apply to the battery used.

It is a hardware block diagram of the assembled battery capacity adjustment apparatus which concerns on this embodiment. It is explanatory drawing of the charging rate used as a target, (a) shows an initial state, (b) has shown the state after adjustment. It is a flowchart which shows the capacity | capacitance adjustment method of the assembled battery which concerns on this embodiment. It is explanatory drawing about the input / output possible range of an assembled battery. It is explanatory drawing of a threshold value, and has shown the correlation with the amount of energy loss and a reference voltage, and the correlation with internal resistance. It is a detailed explanatory view of step ST7 shown in FIG. It is a figure which shows an example of a prior art, and has shown the circuit structure which adjusts a charging rate uniformly. It is explanatory drawing which shows the correlation of an open circuit voltage and a charging rate. It is explanatory drawing which shows the mode of internal resistance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery pack capacity adjustment apparatus 10 ... Vehicle system 11 ... Battery pack 12 ... Current sensor 13 ... Voltage sensor 14 ... Temperature sensor 15 ... Main relay 16 ... Drive motor (load)
17 ... Auxiliary equipment system (load)
20 ... Battery control unit 21 ... Bypass circuit section (bypass circuit means)
22 ... reference voltage unit 23 ... CPU (internal resistance detection means, charge rate control means, calculation means)
24 ... Counter (counting means)
25 ... Memory 30 ... Ignition switch 40 ... Connection switch 50 ... Auxiliary battery 60 ... Vehicle system CPU

Claims (5)

When one of the cells of an assembled battery made up of a plurality of unit cells connected exceeds the reference voltage, the charging rate between the cells is uniformly adjusted by discharging the cell. In the assembled battery capacity adjusting device,
Internal resistance detection means for detecting the internal resistance of the assembled battery;
Charge rate control means for performing control to reduce the charge rate of the assembled battery when the internal resistance detected by the internal resistance detection means is equal to or greater than a threshold;
An assembled battery capacity adjustment device comprising: A counting means for counting the number of times each cell voltage exceeds a reference voltage;
A calculation means for obtaining the adjustment frequency of the charging rate from the number of counts of the counting means;
2. The assembled battery capacity adjustment device according to claim 1, wherein the charging rate control unit performs control to increase a charging rate of the assembled battery when the frequency obtained by the calculating unit is lower than a predetermined value. 3. . A load that operates upon receiving power from the assembled battery;
The charge rate control means reduces the charge rate of the assembled battery by operating the load and increasing the amount of power supplied from the assembled battery to the load. Item 3. The battery pack capacity adjustment device according to any one of Items 2 to 3. Among the cells of the assembled battery, when any voltage exceeds a reference voltage, by further discharging the cell, further comprising a bypass circuit means for adjusting the charging rate between the cells uniformly,
The charging rate control means reduces the charging rate of the assembled battery by discharging each cell by the bypass circuit means when the internal resistance detected by the internal resistance detecting means is greater than or equal to a threshold value. The assembled battery capacity adjustment device according to claim 1 or 2. When one of the cells of an assembled battery composed of a plurality of unit cells is connected and the open circuit voltage exceeds a reference voltage, the cells are discharged to make the charge rate between the cells uniform. In the battery pack capacity adjustment method to be adjusted to
A method for adjusting an assembled battery capacity, comprising: detecting an internal resistance of an assembled battery and determining that the internal resistance is equal to or greater than a threshold value;

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