JP5880162B2 - Charge / discharge control device for battery pack - Google Patents

Description

  The present invention relates to a charge / discharge control device for an assembled battery configured by connecting a plurality of battery cells in series.

  Conventionally, in an electric vehicle such as an electric vehicle (EV) or a hybrid electric vehicle (HEV), an assembled battery in which a plurality of battery cells are connected in series is used to store electric power serving as a power source. For example, in Patent Document 1 below, an equalization circuit for equalizing the capacities of a plurality of single cells (battery cells) and each single cell using the equalization circuit from a state in which the capacities of the single cells are equalized. The voltage of each single cell measured when a large current is passed through the assembled battery is judged as a single cell whose full charge capacity decreases as the voltage of each single cell measured after discharging the same amount An abnormality detection device for a single cell that constitutes an assembled battery including a CPU that determines that the internal resistance value of the single cell has been increased is disclosed.

JP 2003-282156 A

  The battery cells constituting the assembled battery have manufacturing variations in the manufacturing process, capacity variations due to aging, and the like. In the charge / discharge control according to the prior art, the charge capacity is determined according to the battery cell having the maximum battery capacity, and the discharge capacity is determined according to the battery cell having the minimum battery capacity. For this reason, the performance of the assembled battery as a whole is limited to a lower limit product (battery cell having the worst performance) having a variation, that is, the entire assembled battery cannot be fully utilized.

  FIG. 10 is an explanatory diagram schematically showing an outline of the charge control according to the prior art. FIG. 10 shows the battery voltage of each of a plurality of battery cells (cell A to cell E), where (a) shows control during charging and (b) shows control during discharging. Assuming that the operating voltage range of each battery cell is 1.0 V to 3.0 V, the cell B having the highest voltage among the cells A to E is the upper limit voltage (3.0 V) during charging shown in FIG. When it becomes, charge ends. For this reason, other cells cannot be charged even though there is free capacity. Further, during the discharge shown in FIG. 10B, the discharge is terminated when the cell A having the lowest voltage reaches the use lower limit voltage (1.0 V). For this reason, other cells cannot discharge even though there is free capacity.

  FIG. 11 is a charge / discharge curve of a battery cell charged by the method according to the prior art shown in FIG. 11A shows a charging curve, and FIG. 11B shows a discharging curve. The vertical axis represents battery voltage and the horizontal axis represents time. As shown in FIG. 11, the voltage difference is large both at the time of charging and at the time of discharging, it becomes difficult to control, and the battery capacity of each cell cannot be fully utilized. As described above, in the charge / discharge control according to the conventional technology, the battery performance cannot be fully utilized in the assembled battery having a large number of cells and large performance variations (for example, manufacturing variations and aging deterioration variations).

  The present invention has been made in view of the above-described problems of the prior art, and in an assembled battery composed of a plurality of battery cells, the performance variation of each battery cell is reduced, and the battery performance as a whole is improved. An object of the present invention is to provide a charge / discharge control device that can be made to operate.

In order to solve the above-described problems and achieve the object, a battery pack charge / discharge control device according to the present invention is a battery pack charge / discharge control device configured by connecting a plurality of battery cells in series. Determined by the history information acquisition means for acquiring the history information of the assembled battery, the determination means for determining the charge / discharge control value of the assembled battery using the history information acquired by the history information acquisition means, and the determination means Control means for controlling charging / discharging of the assembled battery based on the charged / discharge control value , and the determining means has an upper limit voltage value during charging and a lower limit voltage during discharging as the charge / discharge control value. and determines the value, the set and the charging and discharging control value a value which gave a predetermined margin value based on the use the history information to the limit value of the battery, wherein, of the plurality of battery cells during charge Charging is stopped when the lowest voltage battery cell with the lowest voltage is in the state indicated by the upper limit voltage value, and during discharging, the highest voltage battery cell with the highest voltage among the plurality of battery cells is the lower limit voltage value. to stop discharging when the state shown in, it characterized and this.

According to the present invention, since the charging / discharging control voltage value is a value having a predetermined margin value determined using the history information of the assembled battery, the charging / discharging of the assembled battery is controlled, and at the time of charging Since the control is based on the maximum voltage battery cell at the time of voltage battery cell and discharge, appropriate charge / discharge control can be performed for the battery cell in any state, reducing the variation in performance of each battery cell, Battery performance can be improved as a whole assembled battery.

It is a block diagram which shows the structure of the charging / discharging control apparatus 100 concerning embodiment. It is explanatory drawing which shows the outline | summary of the charging / discharging control voltage value determined by the determination means 132. FIG. It is a graph which shows an example of the setting change of the margin value accompanying the change of a battery characteristic. It is a graph which shows the relationship between a battery temperature and the change of a battery characteristic. It is a graph which shows an example of the addition value depending on temperature. It is a graph which shows the relationship between the storage period of an assembled battery, and the change of a battery characteristic. It is explanatory drawing which shows the outline | summary of the charging / discharging control by the control means 133. FIG. It is a charge curve of the battery cell charged using the charging / discharging control apparatus 100. FIG. 3 is a flowchart showing the operation of the charge / discharge control device 100. It is explanatory drawing which shows typically the outline | summary of the charge control concerning a prior art. It is a charging / discharging curve of the battery cell charged by the method concerning a prior art.

  Exemplary embodiments of a charge / discharge control device for an assembled battery according to the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment)
FIG. 1 is a block diagram illustrating a configuration of a charge / discharge control apparatus 100 according to the embodiment. In the battery cell charge / discharge control apparatus 100 according to the embodiment, charge / discharge of an assembled battery in which a plurality of battery cells 1, 2, 3, 4 are connected in series is controlled. The charging / discharging control device 100 includes a battery pack composed of voltmeters 6, 7, 8, and 9 and battery cells 1, 2, 3, and 4 for monitoring respective voltages of the battery cells 1, 2, 3, and 4. Charging power supply 10 having a DC / DC converter function for charging, ammeters 21, 22, 23, 24 for monitoring respective currents of battery cells 1, 2, 3, 4, and battery cells 1, 2, 3 , 4 for controlling charging / discharging of 4. Although not shown, each battery cell 1, 2, 3, 4 is provided with a temperature sensor, and a detection value by the temperature sensor is output to the BMU 11.

  The BMU 11 includes a CPU, a ROM that stores and stores a control program, a RAM as an operation area of the control program, an EEPROM that holds various data in a rewritable manner, an interface unit that interfaces with peripheral circuits, and the like. The The BMU 11 is a control BMU that controls electric power supplied from a plurality of battery cells 1, 2, 3, 4 to, for example, an electric motor of an electric vehicle. The BMU 11 receives various data, analyzes the received data, and issues various commands. Send.

  Further, the BMU 11 implements a history information acquisition unit 131, a determination unit 132, and a control unit 133 when the CPU executes the control program.

  The history information acquisition unit 131 acquires the assembled battery history information. The history information is, for example, the battery capacity change history after the start of use of the assembled battery or the voltage value when fully charged, the history information of the battery temperature during the use period of the assembled battery, the battery temperature and the storage during the storage period of the assembled battery. For example, history information of the remaining power amount of the battery cell in the period. The history information acquisition unit 131 acquires battery temperature history information by acquiring and storing the detection value of the temperature sensor described above. Further, the history information acquisition unit 131 estimates the remaining power amount of the battery cell from the detection values of the above-described ammeter and voltmeter, and acquires the history information of the remaining power amount.

  The determination unit 132 determines the charge / discharge control value of the assembled battery using the history information acquired by the history information acquisition unit 131. At this time, the determination unit 132 sets a value including a predetermined margin value from the use limit value of the battery cell as the charge / discharge control value. The charge / discharge control value is, for example, an upper limit voltage value during charging (upper limit voltage value during charging) and a lower limit voltage value during discharging (lower limit voltage value during discharging). Hereinafter, the charging upper limit voltage value and the discharging lower limit voltage value are collectively referred to as a charge / discharge control voltage value. For example, when determining the charge / discharge control voltage value as the charge / discharge control value, the determination unit 132 sets the voltage value including a predetermined margin value from the use limit voltage of the assembled battery as the charge / discharge control voltage value.

  FIG. 2 is an explanatory diagram showing an outline of the charge / discharge control voltage value determined by the determining unit 132. The vertical axis in FIG. 2 indicates the battery voltage, and the horizontal axis indicates the battery capacity. Assuming that the working voltage range (usage limit voltage) of the battery cell is 1.0 V to 3.0 V, the charge / discharge control according to the prior art shown by the dotted line in FIG. Was set to 1.0 V, that is, the use limit voltage itself.

  On the other hand, in the charge / discharge control apparatus 100 (determining means 132) according to the present embodiment indicated by a one-dot broken line, values including a predetermined margin value from the use limit voltage are set as the charge upper limit voltage value and the discharge lower limit voltage value. . For example, in the example of FIG. 2, the upper limit voltage value during charging is 2.9 V (margin value 0.1 V), and the lower limit voltage during discharging is 1.1 V (margin value 0.1 V). The reason for providing such a margin value is that the control in the control means 133 described later is different from the charge / discharge control according to the prior art.

  Next, a method for determining the margin value by the determination unit 132 will be described. A battery cell deteriorates over time depending on an elapsed period from the start of use, and its performance changes. Furthermore, there are two types of deterioration over time: use deterioration due to repeated use (charging / discharging cycle) and storage deterioration that occurs even if only storage is performed. The determination unit 132 sets such a margin value that can maximize the performance of the battery cell in consideration of such deterioration of the battery cell. Specifically, the determining means determines a base margin value based on a change in the performance of the battery cell, and determines a margin value by adding an added value considering the temperature and storage deterioration during use to the base margin value. To do.

  FIG. 3 is a graph showing an example of a setting change of the margin value accompanying a change in battery characteristics. In FIG. 3, (a) shows the change in battery characteristics over time, the vertical axis is the capacity retention ratio or the voltage value at full charge, and the horizontal axis is the number of days. Further, (b) shows an example of setting a margin value corresponding to a change in battery characteristics, where the vertical axis is a margin value (initial margin value P), and the horizontal axis is the number of days.

  As shown in FIG. 3A, the assembled battery has a type (type A) that deteriorates after the battery characteristics are improved once after the start of use (type A), and a type (type that deteriorates at a certain rate immediately after the start of use). B) There are various types, such as a type in which the degree of deterioration becomes slow after abrupt deterioration immediately after the start of use (type C), a type that does not deteriorate for a while after the start of use, and a type that deteriorates later (type D) . For this reason, the determination means 132 estimates the deterioration state of the battery cell using the number of days since the start of use of the battery cell and the capacity maintenance rate or the battery voltage value at the time of full charge, and determines the base according to the deterioration state. The margin value is set as shown in FIG.

  In addition, what kind of characteristic change (change in battery capacity or change in voltage value at the time of full charge) of the assembled battery, that is, which type of types A to D in FIG. The battery capacity or the voltage value at the time of full charge may be recorded after the start of use of the battery cell and predicted, or a table that predicts the change in characteristics of the assembled battery is recorded in advance, based on the number of days A predicted value of characteristic change may be read from the table.

Next, the relationship between the battery temperature and deterioration of the assembled battery will be described.
FIG. 4 is a graph showing the relationship between the battery temperature and the change in battery characteristics. FIG. 4 shows changes in battery characteristics when an assembled battery is used under a predetermined temperature condition. (A) shows a capacity maintenance rate, and (b) shows an increase rate of internal resistance. As shown in FIGS. 4 (a) and 4 (b), it can be seen that the deterioration of the assembled battery progresses as the temperature increases in both the capacity retention ratio and the internal resistance. Therefore, the determination unit 132 adds the temperature-dependent addition value to the base margin value as shown in FIG.

  FIG. 5 is a graph showing an example of an addition value depending on the temperature. The vertical axis shows the addition value to the base margin value, and the horizontal axis shows the temperature. As shown in FIG. 5, when the temperature (for example, the average battery temperature during the battery use period) is equal to or higher than a predetermined temperature, the determining unit 132 adds an added value proportional to the temperature to the base margin value. To do. The battery temperature may be measured by providing a temperature sensor for each battery cell, for example, and the average temperature may be calculated, or one temperature sensor for each unit composed of a predetermined number of battery cells or for the entire battery pack You may measure by providing.

  FIG. 6 is a graph showing the relationship (storage period characteristics) between the storage period of the assembled battery and changes in battery characteristics. 6A and 6B show changes in battery characteristics when an assembled battery is stored under a predetermined condition. FIG. 6A shows a capacity retention rate, and FIG. 6B shows an increase rate of internal resistance. As shown in FIGS. 6 (a) and (b), it can be seen that the deterioration of the battery cells progresses as the temperature increases in both the capacity retention ratio and the internal resistance. The storage period characteristics are also related to the charging rate (SOC) of the battery cell, and it can be seen that the deterioration of the assembled battery proceeds as the charging rate is increased. For this reason, when the assembled battery is stored without being used, the determining unit 132 provides an addition value depending on the battery temperature and the charging rate (SOC) during storage and adds the added value to the base margin value. This added value is set so as to increase in proportion to the battery temperature and the charging rate (SOC) during storage.

  Returning to the description of FIG. 1, the control unit 133 controls charging / discharging of the assembled battery based on the charge / discharge control voltage value determined by the determination unit 132. Specifically, when the charge / discharge control value is a charge / discharge voltage value, the control unit 133 determines that the lowest voltage battery cell having the lowest voltage among the plurality of battery cells during charge is the charge / discharge control voltage value (upper charge voltage during charge). ) When charging is stopped, the maximum voltage battery cell having the highest voltage among the plurality of battery cells is indicated by the charge / discharge control voltage value (lower limit voltage during discharge). If the discharge stops.

  FIG. 7 is an explanatory diagram showing an outline of charge / discharge control by the control means 133. FIG. 7 shows the battery voltage of each of a plurality of battery cells (cell A to cell E), where (a) shows control during charging and (b) shows control during discharging. In FIG. 7A, the use upper limit voltage is determined to be 2.9 V (the margin value X1 = 0.1 V) by the determining unit 132. 7B, the use lower limit voltage is determined to be 1.1 V (the margin value X2 = 0.1 V) by the determining unit 132.

  At the time of charging shown in FIG. 7A, the control means 133 stops charging when the cell A (minimum voltage battery cell) having the lowest voltage among the plurality of battery cells reaches the use upper limit voltage of 2.9V. To do. Moreover, at the time of the discharge shown in FIG.7 (b), when the cell B (maximum voltage battery cell) with the highest voltage among several battery cells becomes 1.1V which is a use lower limit voltage, discharge is stopped. As a result, the invalid area is reduced in all cells, and the usable area can be increased. In addition, the control means 133 monitors the voltage of another battery cell, both at the time of charge and at the time of discharge, and controls so that it may not become a dangerous voltage.

  Thus, by setting the operating voltage range with a predetermined margin value from the operating limit voltage, the theoretical module capacity is reduced, but the variation in the voltage of the battery cell is reduced and control is easily performed. , Charging / discharging efficiency (discharge capacity / charge capacity) is high, output variation is small, even when a specific battery cell is deteriorated, it is difficult to lead to a decrease in the performance of the entire assembled battery, and the battery cell is not easily deteriorated. There are advantages such as.

  In FIG. 7, the upper limit side margin value (X1) and the lower limit side margin value (X2) are the same value. However, the upper limit side margin value and the lower limit side margin value are not limited thereto. Different values may be used. When the upper limit side margin value and the lower limit side margin value are different from each other, each value and distribution may be determined based on the assembled battery history information.

  FIG. 8 is a charge curve of a battery cell charged using the charge / discharge control device 100. In FIG. 8, the vertical axis represents battery voltage, and the horizontal axis represents time. As shown in FIG. 8, the voltage difference between the battery cells is reduced and control is facilitated, and the battery capacity of each battery cell can be fully utilized.

Next, the operation of the charge / discharge control apparatus 100 will be described.
FIG. 9 is a flowchart showing the operation of the charge / discharge control apparatus 100. This operation is realized by the BMU 11 executing the flowchart shown in FIG. The determination unit 132 of the charge / discharge control apparatus 100 acquires information on the elapsed period from the start of use of the assembled battery (step S901), and estimates the deterioration state of the assembled battery (step S902). That is, the state in which the battery cell is in FIG. 3A is estimated. Then, based on the estimated deterioration state, a corresponding addition value is selected as shown in FIG. 3B to determine a base margin value (step S903).

  Next, the determination unit 132 determines whether or not the assembled battery is used (step S904), and if used (step S904: Yes), acquires battery temperature information (step S905). Then, the addition value depending on the battery temperature is added to the base margin value (step S906). On the other hand, if not used (step S906: No), the battery temperature information and the charging rate (SOC) information are acquired (step S907), and the base addition value depending on the battery temperature and the charging rate (SOC) is obtained. Add to the margin value (step S908).

  And the determination means 132 determines a charging / discharging control value based on the determined margin value (step S909). The control means 133 performs charge / discharge control of the assembled battery based on the charge / discharge control value determined in step S909 (step S1013), and ends the processing according to this flowchart.

  As described above, according to the charge / discharge control apparatus 100 according to the embodiment, the margin value of the charge / discharge control value is determined based on the history information of the assembled battery, and the charge / discharge control value of the assembled battery is determined using the charge / discharge control value. Control charge and discharge. Thereby, appropriate charge / discharge control can be performed on the battery cells in any state, the performance variation of each battery cell can be reduced, and the battery performance of the assembled battery as a whole can be improved.

  As in the charge / discharge control device 100, by setting the use voltage range with a predetermined margin value from the use limit voltage, the theoretical module capacity is reduced, but the voltage variation of the battery cell is reduced. Battery cells that are easy to control, increase in charge / discharge efficiency (discharge capacity / charge capacity), reduce output variation, and even when a specific battery cell deteriorates, it is difficult to reduce the overall performance of the assembled battery. There are advantages such as less deterioration.

  In the present embodiment, the history information of the entire assembled battery is acquired and the margin value is determined based on the history information. However, the present invention is not limited to this. For example, for each battery cell (or several For each cell module that is a set of battery cells, history information may be acquired and a margin value may be set. In this case, for example, a margin value candidate value is calculated for each individual battery cell (or each cell module), and the largest value among them, that is, the margin based on the history information of the battery cell (cell module) having the smallest capacity is calculated. The value is a margin value of the entire assembled battery. That is, the determination unit 132 determines the charge / discharge control value using the margin value based on the history information of the battery cell having the smallest capacity among the plurality of battery cells.

  1, 2, 3, 4 ... battery cells, 6, 7, 8, 9 ... voltmeter, 10 ... power supply for charging, 11 ... BMU, 21, 22, 23, 24 ... ammeter, 100 ... ... Charging / discharging control device 131 ... History information obtaining means 132 ... Determining means 133 ... Control means

Claims (5)

A charge / discharge control device for an assembled battery configured by connecting a plurality of battery cells in series,
History information acquisition means for acquiring history information of the assembled battery;
Determining means for determining a charge / discharge control value of the assembled battery using the history information acquired by the history information acquiring means;
Control means for controlling charging / discharging of the assembled battery based on the charge / discharge control value determined by the determining means,
The determining means determines an upper limit voltage value at the time of charging and a lower limit voltage value at the time of discharging as the charge / discharge control value, and gives a predetermined margin value based on the history information to the use limit value of the assembled battery . The value is the charge / discharge control value ,
The control means stops charging when a minimum voltage battery cell having the lowest voltage among the plurality of battery cells is in a state indicated by the upper limit voltage value during charging, and among the plurality of battery cells during discharging When the maximum voltage battery cell having the highest voltage is in a state indicated by the lower limit voltage value, the discharge is stopped.
Charge and discharge control of the assembled battery, wherein the this. The history information acquisition means acquires a change history of the battery capacity after the start of use of the assembled battery or the voltage value at the time of full charge,
The charging / discharging control device for an assembled battery according to claim 1, wherein the determining means determines the margin value based on the battery capacity or a change history of a voltage value at the time of full charge. The history information acquisition means acquires battery temperature history information during a period of use of the assembled battery,
The charging / discharging control device for an assembled battery according to claim 1, wherein the determining unit determines the margin value based on history information of the battery temperature. The history information acquisition means acquires battery temperature history information during the storage period of the assembled battery and remaining power amount history information during the storage period,
The charging / discharging control device for an assembled battery according to claim 3, wherein the determining means determines the margin value based on the battery temperature and the remaining power amount during the storage period. The history information acquisition means acquires the history information of each of the plurality of battery cells,
It said determining means 4 by using the margin value based on the history information of the battery cell the most capacity is small among the plurality of battery cells, claim 1, wherein determining said charge-discharge control value The charge / discharge control apparatus of the assembled battery as described in any one of these.

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