JP2020178488A - Balance control device - Google Patents

Abstract

To provide a balance control device capable of appropriately reducing the voltage variation (voltage difference) between battery cells provided in a battery pack.SOLUTION: A balance control device 100 that adjusts and controls the voltage variation of a plurality of battery cells 30 included in a battery pack 10 includes voltage detecting means 110 that detects the voltage of a plurality of battery cells, voltage difference calculation means 141 that calculates the voltage difference of the battery cells, resistance value setting means 142 that sets a target value of the internal resistance of each of the battery cells on the basis of the calculation result of the voltage difference calculation means, and temperature control means 143 that adjusts the individual temperature of each of the battery cells such that the internal resistance of the battery cell approaches the target value.SELECTED DRAWING: Figure 5

Description

The present invention relates to a balance control device that adjusts and controls voltage variations of each battery cell in a battery pack including a plurality of battery cells.

In recent years, many electric vehicles such as electric vehicles and plug-in hybrid vehicles have been put into practical use. A rechargeable secondary battery (for example, a lithium ion secondary battery) is used as a battery for supplying electric power to a traveling motor mounted on an electric vehicle. Further, such a battery is generally mounted on an electric vehicle as, for example, a battery pack (combined battery) in which a plurality of battery cells (secondary batteries) are housed in a case.

In a battery pack having a plurality of battery cells, a voltage difference occurs between the battery cells due to a difference in temperature state and deterioration status between the battery cells while repeating the charge / discharge cycle. .. If a voltage difference occurs between the battery cells, the usable area of the battery pack (battery) may be limited.

Specifically, during charging, charging is stopped when the maximum voltage (maximum cell voltage) of each battery cell reaches the allowable maximum voltage, and during discharging, the minimum voltage (minimum cell voltage) of each battery cell becomes the allowable minimum voltage. When it becomes, the discharge is stopped. Therefore, the smaller the voltage difference between the battery cells constituting the battery pack, the larger the battery capacity originally possessed by the battery pack can be used. Therefore, it is preferable that the voltage difference between the battery cells constituting the battery pack is maintained as small as possible.

In order to solve such a problem, some balancer circuits for discharging the battery cells are provided corresponding to each battery cell. By discharging the battery cells having a high voltage by the resistance of the balancer circuit, the voltage difference (voltage variation) between the battery cells can be reduced (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-191679

Since this balancer circuit is operated, for example, during normal charging of the battery pack, there is a possibility that the voltage variation between the battery cells cannot be sufficiently reduced. Specifically, the magnitude (resistance value) of the resistance of the balancer circuit is constant, and during normal charging of the battery pack, a charging current of a constant magnitude is usually supplied to the battery cell. Therefore, if the voltage variation between the battery cells is large, there is a possibility that the voltage variation between the battery cells cannot be sufficiently reduced only by operating the balancer circuit during normal charging.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a balance control device capable of appropriately reducing voltage variation (voltage difference) between battery cells included in a battery pack. To do.

One aspect of the present invention for solving the above problems is a balance control device for adjusting and controlling voltage variations of a plurality of battery cells included in a battery pack, and a voltage detecting means for detecting the voltages of the plurality of battery cells. , A voltage difference calculating means for calculating the voltage difference of each battery cell, a resistance value setting means for setting a target value of the internal resistance of each battery cell based on the calculation result of the voltage difference calculating means, and a resistance value setting means for each battery cell. The balance control device includes a temperature control means for adjusting an individual temperature of each battery cell so that the internal resistance approaches the target value.

Here, the voltage difference calculating means calculates the difference between the average value of the voltages of the battery cells and the voltage of each battery cell as the voltage difference, and the resistance value setting means has a large voltage difference on the positive side. It is preferable to set the target value to a higher value, and to set the target value to a lower value as the voltage difference is larger on the negative side.

Further, it is preferable that the temperature control means raises the temperature of the battery cell when increasing the internal resistance of the battery cell, and lowers the temperature of the battery cell when lowering the internal resistance of the battery cell.

Further, it is preferable that the temperature controlling means adjusts the individual temperature of the battery cell when the difference between the current value of the internal resistance of the battery cell and the target value is equal to or more than a predetermined value.

Further, each of the battery cells is provided with a heating / cooling means for heating / cooling the battery cells, and the temperature controlling means measures the target temperature of each battery cell so that the internal resistance of each battery cell approaches the target value. It is preferable to individually control the heating / cooling means so that the temperature of each battery cell approaches the target temperature. As the heating / cooling means, for example, it is preferable to use a Peltier element.

Alternatively, a cooling means provided in the case in which the battery cells are housed and for cooling the inside of the case, and a heating means provided in each of the battery cells for individually heating each battery cell are provided. It is preferable that the temperature control means adjusts the individual temperature of each battery cell so that the internal resistance of each battery cell approaches the target value by controlling the cooling means and the heating means.

According to the balance control device of the present invention, the voltage variation (voltage difference) between the battery cells included in the battery pack can be appropriately reduced.

It is a figure which shows an example of the usage mode of the battery pack which concerns on this invention. It is a perspective view which shows the schematic structure of the battery pack which concerns on this invention. It is a perspective view which shows the schematic structure of the battery module which concerns on this invention. It is a figure which shows the appearance of the battery cell which comprises the battery module. It is a figure which shows an example of the schematic structure of the balance control device which concerns on this invention. It is a flowchart which shows an example of the adjustment control of the voltage variation which concerns on this invention. It is a figure which shows another example of the schematic structure of the balance control device which concerns on this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The vehicle 1 shown in FIG. 1 is, for example, an electric vehicle such as an electric vehicle or a hybrid vehicle, and is equipped with a battery pack 10 for supplying electric power to a motor (not shown).

As shown in FIG. 2, the battery pack 10 includes a pack outer case 13 including a pack tray 11 and a pack cover 12, and a battery module 20 housed in the pack outer case 13.

As shown in FIGS. 2 and 3, a plurality of battery modules 20 are housed in the battery pack 10 (pack outer case 13), and each battery module 20 contains a plurality of battery cells (secondary battery cells) 30. It has. Each of these battery cells 30 is connected in series in the pack outer case 13.

Each battery cell 30 is, for example, a sealed secondary battery such as a lithium ion battery, and has a known structure itself, and thus will be briefly described here. As shown in FIG. 4, each battery cell 30 includes a container 31 and a lid member 32 that seals the container 31. Inside the container 31, an electrode body (power generation element) including a positive electrode plate, a negative electrode plate, and a separator is housed together with an electrolytic solution. The lid member 32 is provided with a positive electrode terminal member 33 and a negative electrode terminal member 34, which are connected to the positive electrode plate or the negative electrode plate of the electrode body housed in the container 31, respectively.

Further, as shown in FIG. 5, the battery pack 10 includes a balance control device 100 that adjusts and controls voltage variations of a plurality of battery cells 30 connected in series in this way.

The balance control device 100 performs adjustment control of the voltage variation when the voltage variation of each battery cell 30 (maximum value of the voltage difference of each battery cell 30) exceeds a preset reference value. As will be described in detail later, in the adjustment control of the voltage variation, the temperature of each battery cell 30 is adjusted to change the magnitude of the internal resistance. As a result, the power consumption in each battery cell 30 is adjusted, and the voltage variation in each battery cell 30 is reduced.

In the present embodiment, the balance control device 100 includes a plurality of voltage sensors (voltage detecting means) 110 for detecting the voltage (cell voltage) of each battery cell 30, and a plurality of temperatures for detecting the temperature of each battery cell 30. Detection results of the sensor (temperature detecting means) 120, the Perche element (heating and cooling means) 130 provided in each battery cell 30 for individually heating and cooling each battery cell 30, and the voltage sensor 110 and the temperature sensor 120. A control unit 140 that appropriately controls the Pelche element 130 based on the above is provided.

The configuration of the voltage sensor 110 is not particularly limited as long as it can detect the voltage of each battery cell 30. The configuration of the temperature sensor 120 is not particularly limited as long as it can detect the temperature of each battery cell 30. Further, the heating / cooling means 130 may be any as long as it can heat / cool each battery cell 30 individually, and its configuration is not particularly limited, but a Peltier element is preferably used.

The control unit 140 includes a CPU, a ROM for storing and storing control programs, a RAM as an operating area for the control program, an EEPROM for rewritably holding various data, an interface unit for interfacing with peripheral circuits, and the like. It is configured. The control unit 140 includes a voltage sensor (voltage detecting means) 110 and a temperature sensor (temperature detecting means) 120 provided for each battery cell 30 constituting the battery pack 10, and each Peltier element (heating / cooling means). 130 are connected to each other.

Specifically, the control unit 140 includes a voltage difference calculating means 141, a resistance value setting means 142, and a temperature controlling means 143.

The voltage difference calculating means 141 calculates the voltage difference (difference between the voltage of each battery cell 30 and the reference value) of each battery cell 30 based on the detection result of each voltage sensor 110. In the present embodiment, the voltage difference calculating means 141 calculates the average value Va of the voltage (current value) V1 of each battery cell 30, and uses this average value Va as a reference value, and the voltage difference Vd (=) of each battery cell 30. | V1-Va |) is calculated.

The resistance value setting means 142 sets a target value of the internal resistance of each battery cell 30 based on the calculation result of the voltage difference calculation means 141. Specifically, the resistance value setting means 142 sets the target value Rt of the internal resistance to a lower value as the voltage difference Vd of each battery cell 30 is larger on the positive side, and the internal resistance is set as the voltage difference Vd is larger on the negative side. Set the target value Rt of to a high value.

For example, when the relationship between the voltage (current value) V1 of the battery cell 30 and the average value Va is V1> Va, the resistance value setting means 142 sets the target value Rt of the internal resistance to a value higher than the current value R1. Moreover, the larger the voltage difference Vd (= | V1-Va |), the higher the target value Rt is set. On the other hand, when the relationship between the voltage (current value) V1 of the battery cell 30 and the average value Va is V1 <V, the resistance value setting means 142 sets the target value Rt of the internal resistance to a value lower than the current value R1. Moreover, the smaller the voltage difference Vd (= | V1-Va |), the lower the target value Rt is set.

The temperature control means 143 controls the Peltier element 130 provided in each battery cell 30 to adjust the temperature of each battery cell 30 based on the detection results of the voltage sensor 110 and the temperature sensor 120, and each battery cell 30 adjusts the temperature. Allow the temperature to reach a predetermined temperature.

The temperature control means 143 controls the Peltier element 130 to heat or cool the battery cells 30 so that each battery cell 30 has a predetermined constant temperature set in advance in a normal time when the predetermined conditions are not satisfied.

Further, the temperature control means 143 starts the adjustment control of the voltage variation when the predetermined condition is satisfied, and adjusts the individual temperature of each battery cell 30. In the present embodiment, the temperature control means 143 starts the adjustment control of the voltage variation on the condition that the maximum value of the voltage difference Vd of each battery cell 30 is equal to or more than a preset threshold value, and each battery cell Adjust the individual temperature of 30.

The temperature control means 143 is provided on the condition that the difference between the current value R1 of the internal resistance of the battery cell 30 and the target value Rt (resistance difference Rd = | R1-Rt |) is equal to or greater than a preset threshold value. The adjustment control of the voltage variation may be started.

As the adjustment control of the voltage variation, the temperature control means 143 preferably has a target value Rt so that the current value R1 of the internal resistance of each battery cell 30 approaches the target value Rt set by the resistance value setting means 142. As described above, the individual temperature of each battery cell 30 is adjusted.

In other words, the temperature control means 143 is provided with each battery cell so that the difference (| R1-Rt |) between the current value R1 and the target value Rt of the internal resistance of the battery cell 30 becomes small, preferably zero. Adjust the individual temperature of 30.

The method of adjusting the individual temperature of each battery cell 30 by the temperature controlling means 143 is not particularly limited, but in the present embodiment, the Peltier element (heating / cooling means) 130 provided in each battery cell 30 is appropriately controlled. , The current value R1 of the internal resistance of each battery cell 30 is brought close to the target value Rt.

Specifically, the temperature control means 143 first calculates the target temperature Te1 for the entire battery pack 10 based on the temperature (current value) T1 of each battery cell 30. After that, the individual target temperature Te2 of each battery cell 30 is set so that the internal resistance of each battery cell 30 approaches the target value Rt with reference to the target temperature Te1.

The calculation of the target temperature Te1 by the temperature control means 143 is performed before starting the adjustment control of the voltage variation. When the adjustment control of the voltage variation is not performed, the temperature control means 143 controls each Peltier element 130 so that each battery cell 30 reaches the target temperature Te1.

When adjusting and controlling the voltage variation, the temperature control means 143 uses a Peltier element 130 provided in each battery cell 30 so that the temperature (current value) T1 of each battery cell 30 approaches the target temperature Te2. Control individually. By bringing the temperature of each battery cell 30 close to the target temperature Te2 in this way, the battery pack 10 as a whole approaches the target temperature Te1.

For example, when the relationship between the current value R1 of the internal resistance of the battery cell 30 and the target value Rt is R1> Rt, the temperature control means 143 sets the temperature lower than the target temperature Te1 of the entire battery pack 10 to the battery cell 30. It is set as the individual target temperature Te2 of.

Then, the temperature control means 143 controls the Peltier element 130 to heat or cool the battery cell 30 so that the temperature T1 of the battery cell 30 approaches the target temperature Te2. At that time, the temperature control means 143 preferably sets the target temperature Te2 of the battery cell 30 to a value lower as the resistance difference (| R1-Rt |) is larger.

The internal resistance of the battery cell (hereinafter, also referred to as the first battery cell) whose temperature is adjusted at the target temperature Te2 (<Te1) is, for example, another battery cell whose temperature is adjusted at the target temperature Te1 (hereinafter, also referred to as the first battery cell). It is relatively lower than the internal resistance of the second battery cell).

Therefore, the amount of power consumed by the internal resistance of the first battery cell is relatively smaller than the amount of power consumed by the internal resistance of the second battery cell. Therefore, the voltage drop of the first battery cell is suppressed as compared with that of the second battery cell.

On the other hand, for example, when the relationship between the current value R1 of the internal resistance of the battery cell 30 and the target value Rt is R1 <Rt, the temperature control means 143 sets the temperature higher than the target temperature Te1 of the entire battery pack 10. It is set as the individual target temperature Te2 of the cell 30. Then, the temperature control means 143 heats or cools the battery cell 30 by the Peltier element 130 so that the temperature T1 of the battery cell 30 approaches the target temperature Te2. At that time, it is preferable that the temperature control means 143 sets the target temperature Te2 of the battery cell 30 to a higher temperature as the resistance difference (| R1-Rt |) is larger.

The internal resistance of the battery cell (hereinafter, also referred to as the third battery cell) whose temperature is adjusted at the target temperature Te2 (> Te1) is, for example, the inside of the second battery cell whose temperature is adjusted at the target temperature Te1. It is relatively higher than the resistance.

Therefore, the amount of power consumed by the internal resistance of the third battery cell is relatively larger than the amount of power consumed by the internal resistance of the second battery cell. Therefore, the voltage drop of the third battery cell is promoted as compared with that of the second battery cell.

By performing the adjustment control of the voltage variation in this way and adjusting the individual temperature of each battery cell 30, it is possible to suppress the voltage variation between the battery cells 30.

In the present embodiment, the temperature control means 143 sets the individual target temperature Te2 of the battery cell 30 based on the voltage and the internal resistance of the battery cell 30, and at that time, the charge rate (SOH) of the battery cell 30 is set. ), Deterioration state (SOH), etc., and the target temperature Te2 is preferably set. As a result, an appropriate target temperature Te2 can be set for each battery cell 30.

FIG. 6 is a flowchart showing an example of temperature variation adjustment control by the balance control device 100. Hereinafter, an example of temperature variation adjustment control will be described with reference to FIG.

For example, when the electric vehicle 1 enters the standby state (key-on state), the balance control device 100 starts voltage detection (measurement) together with the temperature of each battery cell 30 (step S1). The timing at which the balance control device 100 starts measuring the voltage of the battery cell 30 is not particularly limited. For example, the voltage measurement may be started at the timing when the occupant manually activates the balance control device 100.

Next, in step S2, the voltage variation of each battery cell 30 is calculated. Specifically, as described above, the voltage difference Vd, which is the difference between the current value V1 and the average value Va of the voltage of each battery cell 30, is calculated. Next, in step S3, it is determined whether or not the maximum value of the voltage difference Vd of each battery cell 30 is equal to or higher than the reference value Vb1 which is a preset threshold value.

Here, if the voltage difference (maximum value) Vd is equal to or greater than the reference value Vb1 (step S3: Yes), the process proceeds to step S4 to perform temperature variation adjustment control. Specifically, in step S5, each battery cell is based on the target temperature Te1 of the entire battery pack 10 determined based on the temperature (current value) T1 of each battery cell 30, the internal resistance of each battery cell 30, and the like. Set 30 individual target temperatures Te2.

Then, in step S6, the Peltier element 130 provided in each battery cell 30 is controlled so that the temperature of each battery cell 30 approaches the individual target temperature Te2. After that, in step S7, it is determined whether or not the voltage difference (maximum value) Vd of each battery cell 30 is smaller than the reference value Vb2 (<Vb1) which is a preset threshold value.

While the voltage difference (maximum value) Vd of each battery cell 30 is equal to or higher than the reference value Vb2 (<Vb1) (step S7: No), the process returns to step S4 and the adjustment control of the voltage variation is continued. After that, when the voltage difference (maximum value) Vd of each battery cell 30 becomes smaller than the reference value Vb2 (<Vb1) (step S7: Yes), the adjustment control of the voltage variation is completed in step S8, and the feedback of the Peltier element 130 is fed back. Stop control.

If the voltage difference (maximum value) Vd is smaller than the reference value Vb1 in step S3 (step S3: No), the process proceeds to step S9, and normal temperature control is performed without performing temperature variation adjustment control. carry out. That is, the Peltier element 130 provided in each battery cell 30 is controlled so that each battery cell 30 reaches the target temperature Te1.

As described above, according to the balance control device 100 according to the present invention, each battery is adjusted by individually controlling the temperature of each battery cell 30 included in the battery pack 10 and adjusting the internal resistance of each battery cell 30. It is possible to suppress the voltage variation (voltage difference) of the cell 30. That is, the voltage of each battery cell 30 can be made uniform.

Further, the adjustment control of the voltage variation according to the present invention can be performed not only while the battery pack 10 is being charged but also when the electric vehicle 1 is running. That is, the adjustment control of the voltage variation can be carried out for a relatively long time. Therefore, the voltage variation of each battery cell 30 can be appropriately adjusted by the internal resistance of the battery cell 30 as well.

Further, in the balance control device 100 according to the present embodiment, since the temperature of each battery cell 30 is adjusted individually, each battery cell 30 can be adjusted to an appropriate temperature. Therefore, deterioration of the battery cells 30 can be suppressed, and uneven deterioration (variation) of each battery cell 30 can be suppressed.

Each battery cell 30 deteriorates as it continues to be used, but the degree of deterioration varies depending on the usage environment. The degree of deterioration of each battery cell 30 may change due to temperature unevenness in the pack outer case 13. For example, if a local temperature rise occurs in the pack outer case 13, the deterioration of the battery cell 30 in the portion where the temperature rises may accelerate. However, by individually adjusting the temperature of each battery cell 30 as described above, it is possible to make the degree of deterioration of the battery cell 30 uniform.

Although one embodiment of the present invention has been described above, the present invention is, of course, not limited to the above-described embodiment.
For example, in the above-described embodiment, the heating / cooling means (Peltier element) 130 is provided in each battery cell 30, and the temperature of each battery cell 30 is adjusted by the heating / cooling means 130. However, the temperature of the battery cell 30 is adjusted. The configuration for adjustment is not particularly limited.

For example, as shown in FIG. 7, the balance control device 100 supplies cold air into the pack outer case 13 in which the battery cells 30 are housed as a configuration for adjusting the temperature of each battery cell 30, and the pack outer case. An air conditioner (cooling means) 150 for cooling the inside of the 13 and a heater (heating means) 160 provided in each of the battery cells 30 for individually heating each battery cell 30 may be provided.

In this case, the temperature control means 143 controls the air conditioner 150 to cool all of the battery cells 30, and selectively controls the heater 160 to heat the predetermined battery cells 30. Even with such a configuration, the temperature of each battery cell 30 can be adjusted to be an individual target temperature Te2, as in the above-described embodiment.

Further, in the above-described embodiment, the balance control device of the present invention has been described by taking a battery pack mounted on an electric vehicle as an example, but the balance control measures of the present invention can also be adopted for battery packs other than those for vehicles. It is a thing.

1 Electric vehicle (vehicle)
10 Battery pack 11 Pack tray 12 Pack cover 13 Pack exterior case 20 Battery module 30 Battery cell 100 Balance control device 110 Voltage sensor (voltage detection means)
120 Temperature sensor (Temperature detection means)
130 Peltier element (heating and cooling means)
140 Control unit 141 Voltage difference calculation means 142 Resistance value setting means 143 Temperature control means 150 Air conditioner (cooling means)
160 heater (heating means)

Claims (7)

It is a balance control device that adjusts and controls the voltage variation of multiple battery cells included in the battery pack.
A voltage detecting means for detecting the voltage of a plurality of the battery cells,
A voltage difference calculation means for calculating the voltage difference of each battery cell,
A resistance value setting means for setting a target value of the internal resistance of each battery cell based on the calculation result of the voltage difference calculation means, and a resistance value setting means.
A balance control device comprising: a temperature control means for adjusting an individual temperature of each battery cell so that the internal resistance of each battery cell approaches the target value. The balance control device according to claim 1.
The voltage difference calculating means calculates the difference between the average value of the voltages of the battery cells and the voltage of each battery cell as the voltage difference.
The balance value setting means is characterized in that the larger the voltage difference is on the positive side, the higher the target value is set, and the larger the voltage difference is on the negative side, the lower the target value is set. Control device. The balance control device according to claim 2.
The temperature control means is characterized in that the temperature of the battery cell is increased when the internal resistance of the battery cell is increased, and the temperature of the battery cell is decreased when the internal resistance of the battery cell is decreased. Balance control device. The balance control device according to any one of claims 1 to 3.
The temperature control means is characterized in that the individual temperature of the battery cell is adjusted when the difference between the current value of the internal resistance of the battery cell and the target value is equal to or more than a predetermined value. apparatus. The balance control device according to any one of claims 1 to 4.
Each of the battery cells is provided with a heating / cooling means for heating / cooling the battery cells.
The temperature control means sets a target temperature of each battery cell so that the internal resistance of each battery cell approaches the target value, and individually heats and cools the means so that the temperature of each battery cell approaches the target temperature. A balance control device characterized by controlling. The balance control device according to claim 5.
A balance control device characterized in that the heating / cooling means is a Peltier element. The balance control device according to any one of claims 1 to 5.
It is provided with a cooling means provided in a case in which the battery cells are housed and for cooling the inside of the case, and a heating means provided in each of the battery cells for individually heating each battery cell. ,
The temperature control means is a balance control device characterized in that by controlling the cooling means and the heating means, the individual temperature of each battery cell is adjusted so that the internal resistance of each battery cell approaches the target value. ..

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