Method for heating up a battery module and cell balancing method using the same

Abstract

To provide a battery-module temperature increase method, capable of efficiently performing both the temperature increase of a battery module that is installed in a vehicle in a cold district and cell balancing on the battery module, and a cell balancing method using the method.SOLUTION: A battery module includes a plurality of cells 12 coupled in series, and resistors 20-1 to 20-4 configured to generate heat after being energized and cause temperature of the cells to be raised. In a battery-module temperature increase method for increasing a temperature of a battery module 10 for a vehicle, voltages and the like of the cells 12-1 to 12-4 being subjected to monitoring and controlling by a cell monitoring unit 14, the resistors 20-1 to 20-4 are configured to generate heat by the voltage supply from part or all of the cells 12-1 to 12-4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for heating a battery module and a cell balancing method using the same method, and particularly to a method for heating a battery module in a cold region and a cell balancing method using the same method.

Background Art

[0002] When the battery module mounted on a vehicle is in an extremely low temperature environment where the outside air temperature is below freezing, the capacity of the battery module decreases, which may cause problems in the running of the vehicle and the like. Therefore, it is necessary to appropriately heat the battery module.

[0003] In addition, the battery module is composed of a plurality of cells, and it is also important to keep the variation in the SOC (State Of Charge) of each cell within a certain range, that is, to achieve "cell balancing" (hereinafter, the balance of the SOC of each cell is referred to as "cell balancing"). If the battery module continues to be used with a large variation in SOC, the deterioration of the cells with a small SOC will progress and the life of the battery module will be shortened.

[0004] In Patent Document 1, in order to heat the battery module, a resistor is attached to a metal bus bar connecting between cells of the battery module, and a voltage is supplied from the outside to the resistor to generate heat.

[0005] FIG. 7 shows a schematic configuration diagram thereof. In the battery module 10, a plurality of cells 12 are connected in series to achieve a predetermined voltage. Each cell 12 has its voltage and the like monitored by a cell monitoring unit 14 via a voltage detection line 18. Resistors are respectively attached to metallic bus bars (not shown) connecting between each cell 12, and for example, four of them are connected in series to form a heater 1 (20-1). The heater 1 is supplied with a voltage from a power supply 28 installed outside through a harness 26 to heat cells 1 to 4.

[0006] In addition, measures to achieve cell balance for the entire cell are usually taken using a resistor (not shown) on the monitoring board within the cell monitoring unit 14. That is, there is a corresponding resistor for each cell, and in order to match a cell with a high SOC to a cell with a low SOC, the cell with a high SOC is consumed by the resistor on the monitoring board.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In the temperature-rising method disclosed in Patent Document 1, a separate power supply for the heater is required externally. Therefore, the harness from the external power supply to the heater becomes long, there is also power loss in the harness, and the temperature-rising efficiency is poor. In addition, in the conventional cell balance method, power is consumed by the resistor on the monitoring board of the cell monitoring unit. However, since the resistor on the monitoring board is not large in capacitance, the power that can be consumed to match a cell with a high SOC to a cell with a low SOC cannot be increased significantly, so it has been taking a long time.

[0009] The present invention has been made in view of the above problems, and an object thereof is to provide a method for raising the temperature of a battery module mounted on a vehicle in a cold region and a cell balance method using the method, which can efficiently perform the temperature-rising and cell balance of the battery module.

Means for Solving the Problems

[0010] In order to achieve the above object, the method for raising the temperature of a battery module according to claim 1 is A battery module heating method for a vehicle battery module, which includes a plurality of cells connected in series and a resistor that is energized to generate heat and raise the temperature of the cells, and in which the voltage and the like of the plurality of cells are monitored and controlled by a cell monitoring unit, the heat generation of the resistor is performed by voltage supply from some or all of the plurality of cells 、 A variable resistor is connected between the resistor and the plurality of cells. Compare the total heat generation amount by the resistor with the heat dissipation amount from the battery module. When the heat dissipation amount is greater than the heat generation amount, set the resistance value of the variable resistor to zero to increase the heat generation amount. When the heat dissipation amount is smaller than the heat generation amount, increase the resistance value of the variable resistor to reduce the difference between the heat generation amount and the heat dissipation amount. is characterized in that.

[0011] According to this method, since the voltage supply to the resistor, which is the heating element for heating the battery module, is performed from the cells themselves that make up the battery module, the harness connected to the resistor can be short, there is no power loss in the harness, and the heating efficiency is high. In addition, an external power source is not required, and since the harness can also be short, the battery module can be configured compactly.

[0013] Also Moreover, since the voltage supplied to the resistor can be adjusted, the amount of heat generated by the resistor can be finely adjusted. That is, when the amount of heat generated by the resistor is large, the resistance value of the variable resistor can be increased to reduce the current value flowing through the resistor, thereby reducing the amount of heat generated, and thereby preventing an unnecessary decrease in the SOC (state of charge) of the cell.

[0015] Furthermore Furthermore, the heat dissipation amount from the battery module and the total heat generation amount of the resistor are compared, and control is performed so that the difference between the heat dissipation amount and the heat generation amount becomes small. Therefore, for example, the time during which the battery module can keep a temperature of 0°C or higher can be calculated. Accordingly, the time during which the performance of the battery module is guaranteed can be known, which contributes to the safe running of the vehicle.

[0016] The claim according to claim 2 1 The cell balancing method using the battery module heating method according to claim The cell monitoring unit measures the SOC of the plurality of cells, and when there is a difference in the level of SOC between the plurality of cells, voltage supply to the resistor is preferentially performed from the cell with a higher SOC.

[0017] As a result, cells with a high SOC (state of charge) are used for heating the battery module and their SOC decreases. On the other hand, cells with a low SOC are not used for heating the battery module, so their SOC is maintained. Therefore, the SOC of cells with a high SOC and cells with a low SOC gradually approaches each other, and the SOC balance is achieved. Furthermore, since a resistor with a relatively small capacity that is not for heat generation in the cell monitoring unit is not used, but a resistor for heat generation with a large capacity is used, the power consumption in the cell can be increased, and the time required to achieve cell balance is short.

Advantages of the Invention

[0018] According to the method for heating the battery module of the present invention and the cell balancing method using the same, the power source for heating the resistor for heating the battery module is the cell of the battery module. Therefore, an external power source is not required and the harness can be shortened, so that the battery module can be configured compactly.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of a method for raising the temperature of the battery module of the present invention and a cell balancing method using the method will be described in detail with reference to the drawings.

[0021] FIG. 1 is an explanatory diagram of a method for raising the temperature of the battery module of the present invention. In the present embodiment, a case where there are 16 cells in the battery module will be described as an example. FIG. 1(a) shows a configuration concept diagram, and FIG. 1(b) shows a schematic plan view.

[0022] The battery module 10 is provided with a cell 12 and a cell monitoring unit 14. The arrangement of each cell is shown in FIG. 1(b). From the left side, the cells are arranged as cell 1, cell 2, cell 3, cell 4, ···, cell 12, cell 13, cell 14, cell 15, cell 16, and they are represented by reference numerals 12-1 to 12-16. The positive electrode of cell 1 and the negative electrode of cell 2 are connected by a metal bus bar 30. Similarly, the positive electrode of cell 2 and the negative electrode of cell 3 are connected by the bus bar 30, and all the cells are electrically connected in series to ensure a predetermined voltage. Voltage detection lines 18 for detecting the voltage of each cell are connected respectively from the negative electrode of cell 1, the connection point between the positive electrode of cell 1 and the negative electrode of cell 2, the connection point between the positive electrode of cell 2 and the negative electrode of cell 3, ···, the connection point between the positive electrode of cell 15 and the negative electrode of cell 16, and the positive electrode of cell 16, and the voltage detection lines 18 are input to the cell monitoring unit 14.

[0023] The resistor as the heating element is connected to the bus bar 30 connecting the poles or attached to the pole. Specifically, one resistor is attached to the negative electrode of cell 1, two resistors are attached to the bus bar connecting the positive electrode of cell 2 and the negative electrode of cell 3, one resistor is attached to the positive electrode of cell 4, and a total of 16 resistors are attached in the same way hereinafter. These resistors are connected in series every four, and respectively constitute heaters 1, 2, 3, and 4. Two harnesses 26 are connected to each heater, one to the cell monitoring unit 14 and the other to the positive electrodes of cells 4, 8, 12, and 16 respectively.

[0024] The cell monitoring unit 14 is provided with various switches, terminals, circuits, etc. (not shown) for monitoring the voltage etc. of each cell, for heating up the battery module 10, and for performing cell balancing described later. In the present embodiment, a switch 1 (22-1) is provided for turning on and off (conducting and non-conducting) one harness 26 connected to the heater 1 (20-1) and the voltage detection line 18 connected to the negative electrode of cell 1 (12-1). Similarly, a switch 2 (22-2) is provided for turning on and off one harness 26 connected to the heater 2 (20-2) and the voltage detection line 18 connected to the connection point of the positive electrode of cell 4 and the negative electrode of cell 5. Similarly hereinafter, switches 3 (22-4) and 4 (22-4) are provided.

[0025] When the switch 1 (22-1) is turned on, the series voltage of cells 1, 2, 3, and 4 is supplied to the heater 1 (20-1). When the switch 2 (22-2) is turned on, the series voltage of cells 5, 6, 7, and 8 is supplied to the heater 2 (20-2). Similarly hereinafter, when switches 3 and 4 are turned on, the series voltage of cells 9, 10, 11, and 12 is supplied to the heater 3, and the series voltage of cells 13, 14, 15, and 16 is supplied to the heater 4.

[0026] When voltage is supplied to the heater 1 (20-1), the heater 1 (20-1) generates heat, and the heat is transferred to cells 1, 2, 3, and 4 to increase the temperature. Similarly, by supplying voltage to heaters 2, 3, and 4, the overall temperature of the battery module 10 is increased.

[0027] The temperature of the battery module 10 can be measured, for example, by attaching a temperature detector 16 such as a thermistor to the cell element of cell 13 (12-13). It is not necessary to attach the temperature detector 16 to all cells. For cells without the temperature detector 16 attached, it is also possible to estimate the temperature from the measured values of other cells.

[0028] In this way, since the voltage supplied to heaters 1, 2, 3, and 4 is configured to be supplied from each cell 12 of the battery module 10, an external power source is not required, and the harness 26 for energizing the heaters can be short, and the voltage drop due to the harness 26 can be ignored. Furthermore, since a resistor with a large capacitance is used to form the heater, it is possible to increase the amount of heat generated. In this way, the temperature of the battery module 10 can be increased efficiently.

[0029] Figure 2 shows another embodiment of the method for increasing the temperature of the battery module. It is basically the same as the circuit shown in Figure 1, but a variable resistor 24 for adjusting the power consumed by the heater is provided in series with the switch 22. By adjusting this variable resistor 24, the voltage supplied to the heater can be changed, and the amount of heat generated by the heater can be adjusted accurately.

[0030] FIG. 3 is an explanatory diagram showing how the cell monitoring unit 14 detects the voltage of each cell and supplies power to the heaters when the temperature rising circuit is configured as shown in FIG. 1 or FIG. 2. The horizontal axis represents time (time point), and each cell 12 is configured to output voltage in time sharing. For example, from time T1 to T2, cells 1 to 4 sequentially output voltage for a short time, and the cell monitoring unit 14 sequentially detects the voltages of cells 1 to 4. From time T2 to T3, cells 1 to 4 are configured to output voltage simultaneously and supply voltage to the heater 1. Similarly, for cells 5 to 8, cells 9 to 12, and cells 13 to 16, time sharing settings are made so that the voltage of each cell can be detected and voltage can be supplied to heaters 2, 3, and 4. In this way, the voltage of each cell is detected and the temperature of the battery module 10 is raised.

[0031] FIG. 4 shows a flowchart of the cell balancing method for the battery module of the present invention. First, the temperature of the battery module and the SOC of each cell are measured (step S1). When the temperature of the battery module is -20°C or lower or the variation in SOC is 3% or more (step S2, Yes), all heating elements, that is, in this embodiment, the switches of heating elements (heaters) 1 to 4 are turned on to raise the temperature of the battery module (step S3). When the temperature of the battery module is -20°C or higher or the variation in SOC is 3% or less (step S2, No), the flow ends.

[0032] The temperature rise of the battery module continues until the temperature of the battery module reaches 0°C or higher (step S4, continue step S3 when No). Note that the temperature of the battery module is configured to be measurable at any time. When the temperature reaches 0°C or higher (step S4, Yes), the SOC of each cell is measured, and it is confirmed whether the variation is 3% or less (step S5). When the variation is 3% or less (step S5, Yes), the switches of all heating elements are turned off and the flow ends (step S7).

[0033] Note that the measurement of SOC (state of charge) can be performed, for example, by measuring the voltage of each cell with a cell monitoring unit and converting it into the state of charge of each cell. Also, it is desirable that the variation in SOC be 3% or less. If the battery module continues to be used with a large variation, the performance of the battery module cannot be fully exhibited, which may hinder the running of the vehicle.

[0034] When the temperature of the battery module reaches 0°C or higher after performing the temperature rise, cell balancing is carried out. However, if the variation of each cell is not 3% or less (step S5, No), the voltage supply from the cell with a high SOC to the resistor is turned on (step S6). Specifically, for example, the circuit shown in FIG. 5 can be adopted. Cells 1 to 16 are connected in series, and resistors R1 to R16 are respectively connected to each cell via switches 32-1 to 32-16. When resistors R1 to R4 are connected in series, they correspond to the heater 1 shown in FIG. 1. The ON / OFF control of the switches is performed by the cell monitoring unit 14.

[0035] For example, when the SOC of cell 1 is 60% and the SOCs of cells 2, 3, and 4 are 65%, if cell 1 continues to be used, the SOC will further decrease, making it difficult to achieve cell balancing. Therefore, in such a case, under the control of the cell monitoring unit 14, switch 32-1 is turned off so that no power is supplied from cell 1. On the other hand, switches 32-2, 32-3, and 32-4 are kept on so that power is supplied from cells 2, 3, and 4.

[0036] By this method, while maintaining the SOC of cell 1 at 60%, cell balancing can be achieved by reducing the SOCs of cells 2 to 4 to 60%. The same control is also performed for cells 5 to 8, cells 9 to 12, and cells 13 to 16, making it possible to achieve cell balancing for all cells.

[0037] In this way, when the variation in SOC becomes 3% or less (FIG. 4, step S5, Yes), the power supply to all heating elements is stopped (step S7), and the process ends.

[0038] FIG. 6 is obtained by adding a flow that guarantees that the battery module can keep a state of 0° C. or higher for a predetermined time to the flow of FIG. 4. Specifically, a flow that guarantees that the battery module can keep a state of 0° C. or higher for a predetermined time is added between step S5 and step S7 of FIG. 4.

[0039] When the variation in SOC between cells becomes 3% or less (step S5, Yes), the average calorific value generated by the heating element for 60 seconds and the heat dissipation amount of the battery module are calculated (step S8). The calculation is performed by, for example, the cell monitoring unit. Since power is supplied to the heating element, which is a resistor or a heater, there is a calorific value. On the other hand, since the outside air temperature is low, heat is sequentially released from the battery module.

[0040] The average calorific value for 60 seconds can be obtained, for example, by measuring the calorific values of all heaters for about 5 minutes and converting them to per 60 seconds. A calorimeter or the like can be used for the measurement. In addition, it is also possible to calculate using the current value flowing through the heater or the like. On the other hand, the heat dissipation amount can also be measured using a calorimeter or the like, and the temperature change of the battery module for 5 minutes can be measured and converted to the heat dissipation amount per 60 seconds using the physical property values (mass, specific heat, etc.) of the battery module. The calorific value and the heat dissipation amount can be obtained by other well-known methods.

[0041] Next, the heat dissipation amount and the calorific value are compared (step S9). If the heat dissipation amount is not greater than the calorific value (step S9, No), the power supply to all the heating elements is stopped and the flow is terminated (step S7).

[0042] If the heat dissipation amount is greater than the calorific value (step S9, Yes), the variable resistor 24 shown in FIG. 2 is adjusted to increase the calorific value (step S10). Specifically, the resistance value of the variable resistor 24 is made closer to zero. Then, considering the outside air temperature and the like, it is calculated whether the battery module can keep a state of 0° C. or higher for a predetermined time (step S11). Here, the predetermined time is, for example, about 3 hours assuming shopping in a shopping mall or the like.

[0043] When the battery module can keep the state of 0°C or higher for a predetermined time (step S11, Yes), the power supply to all the heating elements is stopped and the flow ends (step S7). When the battery module cannot keep the state of 0°C or higher for a predetermined time (step S11, No), the process returns to step S3 and the power supply to all the heating elements continues. Knowing the time during which the battery module can be kept at 0°C or higher means knowing the time during which the performance of the battery module is guaranteed, which contributes to the safe running of the vehicle.

[0044] According to the method for heating up the battery module and the cell balancing method using the method in this embodiment, since the voltage supply to the resistor for heating up the battery module is performed from the cells of the battery module itself, the harness connected to the resistor can be short, there is no power loss in the harness, and the heating efficiency is high. Also, for cell balancing, the resistor for heating up is used, and the voltage supply from the cells with a low SOC to the resistor is not performed, so the time required for balancing can be short. Furthermore, since a variable resistor is connected between the resistor and the cell that supplies power to it, it is possible to adjust the calorific value and perform highly accurate control.

[0045] Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, although the case where the cells of the battery module are 16 is shown, it is not limited to this. Also, there are four heating elements (heaters), one heater is composed of four resistors, and it is configured to be powered by four cells, but it is not limited to this.

Explanation of Reference Numerals

[0046] 10 Battery module 12 Cells 14 Cell monitoring unit 16 Temperature detector 18 Voltage detection line 20 Heating element (heater) 22 Switch 24 Variable resistor 26 Harness 28 External power supply 30 Bus bar 32 Switch R1~R16 Resistors

Claims

1. A method for heating up a battery module for a vehicle, comprising: a plurality of cells connected in series; and a resistor that is energized to generate heat and raises the temperature of the cells, wherein the voltage and the like of the plurality of cells are monitored and controlled by a cell monitoring unit. In this method, the heat generation of the resistor is performed by voltage supply from some or all of the plurality of cells, a variable resistor is connected between the resistor and the plurality of cells, the total heat generation amount by the resistor is compared with the heat dissipation amount from the battery module. When the heat dissipation amount is greater than the heat generation amount, the resistance value of the variable resistor is set to zero to increase the heat generation amount. When the heat dissipation amount is smaller than the heat generation amount, the resistance value of the variable resistor is increased to reduce the difference between the heat generation amount and the heat dissipation amount. A method for heating up a battery module, characterized by the above.

2. The cell balance method using the method for heating up a battery module according to claim 1, characterized in that the cell monitoring unit measures the SOC of the plurality of cells, and when there is a difference in the level of SOC between the plurality of cells, voltage supply to the resistor is preferentially performed from the cell with a higher SOC.

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