JP7447748B2 - Battery control method and control device - Google Patents

Description

The present invention relates to a battery control method and control device.

Batteries (secondary batteries) are discharged or charged depending on the usage conditions, but in order to suppress battery deterioration, it is necessary to prevent overcharging and overdischarging. Therefore, the SOC (ratio of remaining capacity to full charge capacity) of the battery is limited to, for example, a range of 30% to 70%.

In a battery formed by connecting a plurality of cells in series, the state of charge of each cell changes individually over time, causing variations among the cells. Cells with a small charging capacity reach the end-of-discharge voltage first when the battery discharges, so it is necessary to stop discharging at that point and move on to a charging cycle even if other cells have surplus capacity. On the other hand, since a cell with a large charging capacity reaches the end-of-charge voltage first when charging the battery, it is necessary to stop charging at that point even if there is room for charging other cells.

Patent Document 1 discloses that in order to balance the voltage between a plurality of cells connected in series, the voltage of each cell is detected, high voltage cells and low voltage cells are identified, and charge is transferred from the high voltage cell to the low voltage cell. It is stated that it can be moved.

Patent Document 2 discloses that a battery formed by connecting a plurality of cells in series is equipped with a fan or a Peltier element for cooling the battery, and the fan or the Peltier element is supplied with electricity from the cell with a higher SOC to cool the battery and balance the cells. It is stated that

Japanese Patent Application Publication No. 2013-70486 Japanese Patent Application Publication No. 2015-119605

From the viewpoint of increasing the effective capacity of the battery, it is preferable to perform cell balancing as appropriate. However, on the other hand, in a battery, the temperature of some cells may rise more than other cells due to self-heating caused by battery reactions. In that case, the cell deteriorates quickly, shortening the life of the entire battery. As in Patent Document 2, using cells with a high SOC to cool the battery is one way to extend battery life, but cooling the entire battery is not efficient and requires a large amount of power. do.

Therefore, an object of the present invention is to perform cell balancing while using as little power as possible to counter battery deterioration due to cell temperature rise.

In order to solve the above problem, the present invention utilizes the extra power of cells with a high SOC to cool only the cells whose temperature has become high, and performs cell balance with the remainder of the extra power.

The battery control method disclosed herein is a battery control method in which a plurality of parallelly arranged chargeable and dischargeable cells are connected in series, and includes:
A Peltier element is provided between adjacent cells of the plurality of cells, which transfers heat from one cell to the other cell by energization,
Detecting the SOC or voltage of each of the plurality of cells;
detecting the temperature of each of the plurality of cells;
When there are variations in the SOC or voltage of the plurality of cells and there is a high temperature cell among the plurality of cells whose temperature exceeds a predetermined threshold, a low temperature cell whose temperature is relatively low next to the high temperature cell energizing the Peltier element between the high temperature cell and the low temperature cell from the cell with the highest SOC or voltage to transfer heat to;
After the step of energizing the Peltier element, the battery is characterized by a step of redistributing the charge of the cell with the highest SOC or voltage to each cell of the battery.

Further, the battery control device disclosed herein is a battery control device formed by connecting a plurality of chargeable/dischargeable cells arranged in parallel in series,
a Peltier element that is provided between adjacent cells of the plurality of cells and that transfers heat from one cell to the other cell when energized;
A cell balancing circuit that redistributes the charge of the cell with the highest SOC or voltage among the plurality of cells to each cell of the battery;
A heat transfer circuit that causes the charge of the cell with the highest SOC or voltage among the plurality of cells to flow through the Peltier element to transfer the heat;
The SOC or voltage and temperature of each of the plurality of cells are detected, and when there are variations in the SOC or voltage of the plurality of cells and there is a high temperature cell among the plurality of cells whose temperature exceeds a predetermined threshold. , the heat is transferred between the cell with the highest SOC or voltage and the Peltier element so that heat is transferred from the high temperature cell to the adjacent low temperature cell whose temperature is relatively low via the Peltier element between both cells. a controller that connects the cell with the highest SOC or voltage to the cell balancing circuit so that the charge redistribution occurs after performing the process of lowering the temperature of the high temperature cell; It is characterized by having

According to such a control method or control device, electricity is applied from the cell with the highest SOC or voltage only to the Peltier element that cools the high-temperature cell that exceeds the threshold, so the high-temperature cell is cooled with less power and the entire battery is It can extend the lifespan. Then, after cooling the high-temperature cell, the charge of the cell with the highest SOC or voltage is redistributed to each cell, so this cell balance can increase the effective capacity of the battery. Here, the energization to the Peltier element becomes passive (discharge type) balancing, and the redistribution of the charge becomes active balancing. Therefore, in the present invention, cell balancing is performed by both.

In one embodiment of the control method and control device, the temperature of each cell is detected by a sensor, and the amount of temperature increase expected to increase due to heat generation of each cell when the charge is redistributed is added to the detected temperature. Taking this into consideration, determine the temperature of each cell.

This is advantageous in reliably suppressing deterioration of the cell due to temperature rise.

In one embodiment of the control method and control device, when the temperature of the cell with the highest SOC or voltage is below a predetermined value, energization from the cell to the Peltier element and redistribution of the charge are prohibited.

When the temperature of the cell is low, its internal resistance increases, so power consumption for energizing the Peltier element and redistributing charge increases. The purpose is to prohibit energization of the Peltier element and redistribution of charge in order to avoid deterioration of energy efficiency.

In one embodiment of the control method and control device, the prohibition of energization of the Peltier device and redistribution of the charge is performed when the SOC or voltage of the cell with the highest SOC or voltage is below a predetermined value, and the above-mentioned The condition is that the SOC or voltage of the cell with the lowest SOC or voltage is equal to or higher than a predetermined value.

That is, when there is a cell with an excessively high SOC or voltage, or when there is a cell with an excessively high SOC or voltage, energization to the Peltier element and charge redistribution based on the temperature of the cell are not prohibited.

When there is a cell with an excessively high SOC or voltage, even if an attempt is made to store external energy in the battery as electric power, the capacity of the cell will soon be exceeded, and the energy that cannot be stored will be wasted. For example, if the battery is used to supply power to a motor that drives a vehicle, when the motor is put into regenerative operation as a generator due to a change in the vehicle's driving conditions, the battery will quickly exceed its capacity. regenerative operation becomes impossible. In this case, when comparing the energy loss due to the inability to perform regenerative operation with the energy loss due to power transfer when the cell temperature is low (internal resistance is high), the former usually has a larger loss. be.

Therefore, if there is a cell with an excessively high SOC or voltage, it is possible to energize the Peltier element and redistribute the charge in order to prioritize securing a charging slot, regardless of the temperature of that cell. Make it.

Further, if there is a cell with an excessively low SOC or voltage, the battery cannot be discharged even if other cells have discharge capacity. Therefore, by enabling the redistribution of the charge, it is possible to maintain the discharged state of the battery as much as possible by using other cells that have discharge capacity.

In one embodiment of the control method and control device, the battery is used to supply power to a motor that drives a vehicle,
The threshold value related to the temperature of the cell when the switch for operating and stopping the power train including the motor of the vehicle is off and on is different, and the threshold value when it is off is different from the threshold value when it is on. higher than the threshold at some point.

While the vehicle is running, the battery is used under a high load and the cell may become hot (progressing deterioration). Therefore, in order to avoid this, the threshold value for cooling by the Peltier element is lowered when the switch is turned on. On the other hand, when the vehicle is not running, there is a low possibility that the temperature of the cell will increase, and it is expected that the temperature will decrease due to natural cooling. Therefore, by increasing the threshold value, power transfer (energization to the Peltier element) is avoided as much as possible, and power consumption is suppressed.

In one embodiment of the control method and control device, it is determined whether the degree of cooling requirement of the high temperature cell is high or low based on the temperature of the high temperature cell;
When the degree of cooling demand is high, electricity is applied to each of the low-temperature cells on both sides of the high-temperature cell and the Peltier element between the high-temperature cells, and when the degree of cooling demand is low, the low-temperature cells on both sides of the high-temperature cell are energized. The Peltier element between the low temperature cell whose temperature is lower and the high temperature cell is energized.

Heat transfer by the Peltier element becomes more efficient as the temperature difference between cells increases, but when rapid cooling of the cells is required, priority is given to rapid cooling of the cells over efficiency.

According to the present invention, a high temperature cell is identified using the power of the cell with the highest SOC or voltage, cooling is performed by a Peltier element between the cells, and the charge of the cell with the highest SOC or voltage is reduced to each cell. Since the power is redistributed to the cells, it is possible to efficiently balance the cells while cooling the cells with the minimum amount of power. That is, it is possible to efficiently prevent battery deterioration and improve the effective capacity of the battery.

A configuration diagram of main parts of a vehicle equipped with a battery. FIG. 3 is a schematic plan view showing a cooling structure using a battery fan. FIG. 3 is a front view showing a part of the battery module. Cell balancing/heat transfer circuit diagram. A diagram showing a control system for cell balancing and heat transfer. Control flow diagram for cell balancing and heat transfer.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on drawing. The following description of preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its applications, or its uses.

<Vehicles equipped with batteries>
The vehicle 1 illustrated in FIG. 1 is a so-called hybrid vehicle. The vehicle 1 is equipped with an engine 2, a motor generator 3, a battery 4, a PCM 5, and the like. The motor generator 3 includes an inverter 20, a motor 30, and the like. Engine 2 is a well-known internal combustion engine that generates power for vehicle 1 by burning fuel. A crankshaft 2a of the engine 2 is connected to a rotating shaft 30a of a motor 30 via a clutch 6. A rotating shaft 30a of the motor 30 is connected to a drive wheel 1a of the vehicle 1 via a transmission 7 and a differential gear 8. The engine 2, motor generator 3, clutch 6, transmission 7, and differential gear 8 constitute a power train of the vehicle 1.

When the engine 2 is operated with the clutch 6 engaged, the vehicle 1 can be driven (run) by the engine 2. When the motor 30 is operated with the clutch 6 disengaged, the vehicle 1 can be driven by the motor 30. When the engine 2 and the motor 30 are operated with the clutch 6 engaged, the vehicle 1 can be driven by both the engine 2 and the motor 30.

By disengaging the clutch 6 when braking the vehicle 1, the motor 30 can be rotated by the rotational force of the drive wheels 1a. Thereby, the motor 30 can function as a generator, and kinetic energy can be recovered to the battery 4 as electrical energy. This vehicle 1 is a parallel hybrid vehicle.

The battery 4 is a rechargeable battery that can be charged and discharged. The battery 4 is electrically connected (hereinafter also simply referred to as connection) to a motor 30 via an inverter 20. The inverter 20 converts DC power into AC power and outputs it. Inverter 20 controls the operation of motor 30.

PCM 5 is a power train control module, and is connected to engine 2, inverter 20, and the like. Various sensors are connected to the PCM 5 to detect the operating states of the engine 2 and motor 30 in order to control the power train.

<Cooling device for the entire battery>
As shown in FIG. 2, the battery 4 includes battery modules 51 to 59, and each of the battery modules 51 to 59 is accommodated therein, and is fixed to a substantially central portion of a floor panel (not shown) of the vehicle 1 in the longitudinal direction of the vehicle. It has a battery case 60.

Each of the battery modules 51 to 59 is attached with a module temperature sensor 61 for detecting the respective temperature and a module voltage sensor 62 for detecting the respective voltage. The battery modules 51 to 59 are connected in series, and one battery module 57 is provided with a module current sensor 63 for detecting the current value flowing through each battery module 51 to 59.

The battery case 60 is formed in the shape of a rectangular parallelepiped with a housing space 60a inside, and is arranged with its longitudinal direction aligned with the vehicle width direction and its height direction aligned with the vertical direction.

The battery modules 51 to 59 are arranged in a first module row 90 consisting of three battery modules 51 to 53 arranged in the longitudinal direction of the vehicle, a second module row 91 consisting of three battery modules 54 to 56 arranged in the same manner, and three battery modules arranged in the same manner. There are three rows of third module rows 92 consisting of three battery modules 57 to 59. These three rows are lined up in the vehicle width direction.

Three air intake ports 70 to 72 are formed in the vehicle front side surface 60b of the battery case 60 to introduce air into the battery case 60 by driving a cooling fan 65, which will be described later. Three air exhaust ports 73 to 75 are formed on the vehicle rear side surface 60c of the battery case 60 to discharge air taken into the case 60 from the air intake ports 70 to 72.

Each of the air intake ports 70 to 72 is arranged to face each of the module rows 90 to 92 in the front and back. Similarly, each of the air exhaust ports 73 to 75 is arranged to face each of the module rows 90 to 92 in the front and back.

Each of the air intake ports 70 to 72 is provided with shutters 80 to 82 that slide up and down to open and close the air intake ports 70 to 72. Each of the air outlets 73 to 75 is provided with shutters 83 to 85 that slide up and down to open and close the air outlets 73 to 75. The shutters 80 to 85 are driven by motors, and their operation is controlled by a battery controller 64 housed in the battery case 60.

An air introduction duct 76 for guiding air to the air intake ports 70 to 72 is connected to the vehicle front side surface 60b of the battery case 60. An air exhaust duct 77 is connected to the vehicle rear side surface 60c of the battery case 60 for guiding air discharged from the three air exhaust ports 73 to 75 to the rear of the vehicle. The air exhaust duct 77 is provided with a cooling fan 65 for guiding air into the battery case 60. The operation of the cooling fan 65 is controlled by the battery controller 64.

<Battery module structure>
As shown in FIG. 3, each of the battery modules 51 to 59 includes a plurality of chargeable and dischargeable square cells 11 and a Peltier element 12 housed in a module case 10. The plurality of cells 11 are arranged in parallel so that the front surface and the rear surface, which have the largest area, face each other, and are connected in series. The Peltier element 12 is a combination of a plurality of n-type semiconductors, a plurality of metals, and a plurality of p-type semiconductors interposed between opposing ceramic plates.

The Peltier element 12 is interposed between adjacent cells 11, with a ceramic plate on one side in contact with the front surface of one cell 11, and a ceramic plate on the opposite side in contact with the rear surface of the other cell 11, respectively. When the Peltier element 12 is energized in one direction, the ceramic plate on one side becomes a heat-absorbing surface and the ceramic plate on the other side becomes a heat-radiating surface, and when energized in the other direction, the ceramic plate on one side becomes a heat-radiating surface and the ceramic plate on the other side becomes a heat-radiating surface. The ceramic plate becomes the heat absorbing surface.

<Cell active balancing/cooling circuit>
The battery controller 64 performs balancing of the cells 11 of each of the battery modules 51 to 59 using the balancing/heat transfer circuit 40 shown in FIG. 4 and cooling of the cells 11 using the Peltier element 12. To put it simply, the surplus energy of the high SOC cell is used for cooling the cell 11 by the Peltier element 12 by utilizing the power extraction circuit of the cell balancing circuit. The circuit 40 is provided in each of the battery modules 51 to 59 (hereinafter collectively referred to as "battery module M").

The circuit 40 of this example is formed by adding a heat transfer circuit 42 to a transformer type cell balancing circuit 41. The cell balancing circuit 41 includes one transformer 43, a primary coil switch SW1 provided at one end of the primary coil 43a of the transformer 43, a secondary coil switch SW2 provided at one end of the secondary coil 43b of the transformer 43, A primary coil switching circuit 44 is provided. The switches SW1 and SW2 are, for example, semiconductor switches such as MOSFETs, and their on/off operations are controlled by signals from the battery controller 64.

The primary coil 43a of the transformer 43 is connected to the positive and negative electrodes of a selected cell (high SOC cell) 11 of the battery module M. Alternative connection of the cell 11 to the primary coil 43a is performed by a primary coil switching circuit 44. That is, the primary coil switching circuit 44 is a circuit that selectively switches the cell 11 to which the primary coil 43a is connected via the primary coil switch SW1, and its operation is controlled by a signal from the battery controller 64. The secondary coil 43b of the transformer 43 is connected to the positive and negative electrodes of the battery module M via a secondary coil switch SW2 and a changeover switch SW3.

The changeover switch SW3 is a switch that selectively switches the connection of the secondary coil 43b of the transformer 43 between the cell balancing circuit 41 and the heat transfer circuit 42.

The heat transfer circuit 42 includes a secondary coil switching circuit 45 that selectively switches which Peltier element 12 is energized from the secondary coil 43b of the transformer 43, and an energization direction switching circuit that switches the direction of energization from the secondary coil 43b to the Peltier element 12. A circuit 46 is provided. The secondary coil switching circuit 45 is a circuit that selectively switches the Peltier element 12 connected to the secondary coil 43b via the secondary coil switch SW2, and its operation is controlled by a signal from the battery controller 64. The energization direction switching circuit 46 includes two interlocking switches SW4 and SW5 for switching the energization direction, and is provided in each Peltier element 12. The operation of the interlocking switches SW4 and SW5 is controlled by a signal from the controller 64.

The heat transfer circuit 42 includes a circuit that selectively connects the primary coil 43a of the transformer 43 to the cell (high SOC cell) 11 of the battery module M by a primary coil switching circuit 44, and a circuit that connects the secondary coil 43b of the transformer 43 to the cell (high SOC cell) 11 of the battery module M. It can be said that the secondary coil switching circuit 45 is configured by a circuit that is selectively connected to the Peltier element 12 between the cells by the secondary coil switching circuit 45.

In the balancing/heat transfer circuit 40, the primary coil 43a of the transformer 43 is connected to a specific cell (high SOC cell) 11, and the secondary coil 43b is connected to the cell balancing circuit 41 by the changeover switch SW3 as shown by the chain line. When connected, cell balancing can be performed. That is, as follows.

The primary coil switch SW1 and the secondary coil switch SW2 are turned on alternately. When the primary coil switch SW1 is on (the secondary coil switch SW2 is off), a current A1 flows from the specific cell 11 to the primary coil 43a of the transformer 43, and the core of the transformer 43 is magnetized. When the secondary coil switch SW2 is turned on (the primary coil switch SW1 is turned off), an induced current is generated in the secondary coil 43b by the magnetized core of the transformer 43, and the induced current flows into the battery module M as shown by arrow A2. flows.

Thereby, charge is redistributed from the specific cell 11 to all the cells 11 of the battery module M. Active balancing of the cells 11 is achieved by controlling the times during which switches SW1 and SW2 are alternately turned on.

Next, when the secondary coil 43b of the transformer 43 is connected to the heat transfer circuit 42 as shown by the solid line by the changeover switch SW3, heat can be transferred between adjacent cells 11 via the Peltier element 12. That is, as follows. When the interlocking switches SW4 and SW5 of the energization direction switching circuit 46 are in the state shown by the solid line in FIG. The current flows to the Peltier element 12 as shown in FIG. As a result, heat moves from one cell 11 to the other cell 11 adjacent to each other with the Peltier element 12 in between. In this case, one cell 11 is cooled and the other cell 11 is heated.

When the interlocking switches SW4 and SW5 of the energization direction switching circuit 46 are switched as shown by the chain lines in FIG. flows. As a result, heat moves from the other cell 11 to one cell 11 adjacent to each other with the Peltier element 12 in between. That is, one cell 11 is heated and the other cell 11 is cooled.

<Battery cell balance and cell cooling control by battery controller>
As shown in FIG. 5, in order to control cell balancing and cell cooling by the battery controller 64, the cell voltage detection circuit 47, the cell temperature detection circuit 48, the operation switch 49, and the internal resistance detection means of the battery module M are connected to the battery controller 64. It is connected to the.

The cell voltage detection circuit 47 is connected to each node of a plurality of series-connected cells 11 through a plurality of voltage lines, and detects the voltage of each cell 11 by detecting the voltage between two adjacent voltage lines. do.

The cell temperature detection circuit 48 detects the temperature of each cell 11 based on a resistance change of a temperature detection element (temperature sensor) such as an NTC thermistor provided in each cell 11.

The operation switch 49 is a switch for operating the power train of the vehicle 1 and stopping it. Further, a current value flowing through the battery module M detected by a current detection circuit (not shown) is input to the battery controller 64.

The battery controller 64 includes a microcomputer and memory (eg, EEPROM, flash memory). The memory includes a SOC-OCV (open circuit voltage) map.

The SOC of each cell 11 is estimated based on the voltage, current, and temperature of each cell 11. SOC can be estimated by, for example, the OCV method or the current integration method. The OCV method is a method of estimating the SOC based on the OCV of the detected cell and the characteristic data of the SOC-OCV curve. The current integration method is a method of estimating the SOC based on the detected OCV at the start of charging/discharging of the cell 11 and the integrated value of the detected current.

The battery controller 64 executes cell balance processing, heat transfer processing, and cooling fan operation processing based on the SOC of each cell 11 of the battery module M, the temperature of each cell 11, and the internal resistance of the battery module M.

Cell balance processing is executed when there is a variation in SOC between cells that exceeds a predetermined value α (for example, 3%). That is, when the SOC difference ΔSOC between the high SOC cell 11 with the highest SOC and the low SOC cell 11 with the lowest SOC exceeds the predetermined value α, the cell balancing process is executed by the cell balancing circuit 41.

The heat transfer process is performed when there is the above-mentioned variation in SOC between cells, and when there is a cell 11 (cell requiring cooling) whose predicted temperature exceeds a predetermined value Tc, the predicted temperature of the battery module M described below is This is executed by the heat transfer circuit 42 prior to the cell balance process under the condition that Tb is less than or equal to the predetermined value Tb.

The "predicted temperature" is a temperature obtained by adding the amount of temperature increase that is expected to increase due to heat generation of the cell 11 when cell balance is executed to the detected temperature (actually measured value) of the cell 11 by the cell temperature detection circuit 48. Note that the detected temperature of the cell 11 may be used to determine whether or not to perform cooling processing such as heat transfer.

The predetermined value Tc differs depending on whether the driving switch 49 of the vehicle is on or off, and "predetermined value Tcd when on is smaller than predetermined value Tcs when off." Tcd can be, for example, 45°C, and Tcs can be, for example, 55°C.

In the heat transfer process, the mode of heat transfer changes depending on whether or not rapid cooling of the cell 11 is required. That is, when the cell 11 needs to be rapidly cooled, the Peltier elements 12 arranged on both sides of the cell 11 are energized so that heat is transferred to the cells 11 on both sides of the cell 11. On the other hand, when rapid cooling of the cell 11 is not required, the Peltier element 12 on one side of the cell 11 where the temperature is low is transferred so that heat is transferred to the cell 11 with a lower temperature among the cells 11 on both sides of the cell 11. Power is applied. The Peltier element 12 is energized for a period of time necessary for the predicted temperature of the cell 11 to drop below the predetermined value Tc. The time is calculated based on the temperature difference between the predicted temperature of the cell 11 and the predetermined value Tc, and data representing the relationship between the energization time to the Peltier element 12 and the amount of cell temperature drop, which has been experimentally determined in advance.

Whether or not rapid cooling of the cell 11 is required is determined based on the predicted temperature of the cell 11. That is, when the operation switch 49 is on, rapid cooling is determined to be necessary when the predicted temperature of the cell 11 exceeds a temperature (eg, 50° C.) higher than the predetermined value Tcd (eg, 45° C.). When the operation switch 49 is off, rapid cooling is determined to be necessary when the predicted temperature of the cell 11 exceeds a temperature (eg, 60° C.) higher than a predetermined value Tcs (eg, 55° C.).

After the heat transfer process is executed for the required time, the heat transfer process is shifted to the cell balance process.

The cooling fan 65 is activated when the internal resistance of the battery module M is equal to or higher than a predetermined value. That is, when a module with a large internal resistance is detected among the battery modules 51 to 59, the shutters of the air intake and air outlet of the module row in which that module exists are opened in order to delay the deterioration of the module. At the same time, the cooling fan 65 is activated.

Further, the cooling fan 65 is activated when the predicted temperature of the battery module M exceeds a predetermined value Tb. This predetermined value Tb differs depending on whether the driving switch 49 of the vehicle is on or off, and is "predetermined value Tbd when on<predetermined value Tbs when off." Tbd can be, for example, 45°C, and Tbs can be, for example, 55°C.

The predicted temperature of the battery module M is estimated based on the predicted temperature of the specific cell 11. For example, the temperature of the cells 11 located at the ends of the battery module M is expected to be lower than that of the cells 11 located at the center. Therefore, when the predicted temperature of the cell 11 located at the end exceeds the predetermined value Tb, it is estimated that the predicted temperature of the battery module M exceeds the predetermined value Tb. Alternatively, when the predicted temperatures of the plurality of cells 11 exceed the predetermined value Tb, it is estimated that the predicted temperature of the battery module M exceeds the predetermined value Tb.

In this case, when the predicted temperature of the battery module M exceeds the predetermined value Tb, the shutters of the air intake and air outlet of the module row in which the module exists are opened, and the cooling fan 65 is operated. When the shutters of the air inlet and air outlet of the module row have already been opened and the cooling fan 65 is operating based on the internal resistance of the battery module M, the cooling fan 65 is controlled to increase the air volume. Ru. When the shutters of the air intake ports and air exhaust ports of other module rows are open, the shutters of the air intake ports and air exhaust ports of the module row are opened, and the air volume of the cooling fan 65 increases. controlled as follows.

The cell balance process and the heat transfer process are prohibited when the detected temperature of the high SOC cell 11 is below a predetermined value TL (for example, 10° C.). However, when the SOC (high SOC) of the high SOC cell 11 is higher than the predetermined value SH (for example, 70%), or when the SOC (low SOC) of the low SOC cell 11 is less than the predetermined value SL, the high SOC This prohibition is not performed regardless of the temperature of the cell 11.

<Control flow by battery controller>
The control flow is shown in FIG. In step S1 after the start, the SOC of each cell 11 is determined based on the voltage, current, and temperature of each cell 11, and in step S2, the temperature of each cell 11 is determined. In the following step S3, it is determined whether the SOC difference ΔSOC between the high SOC cell 11 and the low SOC cell 11 exceeds a predetermined value α.

When ΔSOC exceeds the predetermined value α, the process advances to step S4, and it is determined whether the high SOC, which is the SOC of the high SOC cell 11, exceeds the predetermined value SH, or the low SOC, which is the SOC of the low SOC cell 11, is less than the predetermined value SL. It is determined whether or not. When the high SOC is below the predetermined value SH and the low SOC is above the predetermined value SL, the process proceeds to step S5, where it is determined whether the detected temperature of the high SOC cell exceeds the predetermined value TL. When the detected temperature of the high SOC cell exceeds the predetermined value TL, the process proceeds to step S6 (cell temperature prediction step).

Further, in step S4, when the high SOC exceeds the predetermined value SH or when the low SOC is less than the predetermined value SL, the process proceeds to step S6 (cell temperature prediction step) without checking the cell temperature in step S5. move on.

The cell temperature prediction in step S6 is a prediction of the temperature of each cell 11 when cell balance is executed as described above. Based on this predicted temperature, it is determined whether or not to operate the cooling fan 65 and whether or not to cool the cell 11 by the Peltier element 12 before cell balancing.

In step S5, when the detected temperature of the high SOC cell is below the predetermined value TL, the process returns without proceeding to step S6 (cell temperature prediction step). This is because when the cell temperature is low, the internal resistance is large, so the power consumption for energizing the Peltier element 12 and redistributing charges (cell balance) becomes large. The purpose is to prohibit energization of the Peltier element 12 and redistribution of charge in order to avoid deterioration of energy efficiency.

On the other hand, when the high SOC exceeds the predetermined value SH or when the low SOC is less than the predetermined value SL, proceeding to the cell temperature prediction step without checking the cell temperature (steps S4-S6) is due to cell balance. This is because the demand for execution is high.

Specifically, if there is a cell 11 with an excessively high SOC, when the motor 30 is put into regenerative operation using as a generator due to a change in the running condition of the vehicle 1, the capacity will be immediately exceeded and the regenerative operation will be started. be unable to do so. Therefore, when the SOC of the cell 11 is excessively high, it is possible to energize the Peltier element and redistribute the charge in order to give priority to securing a charging slot, regardless of the cell temperature.

Moreover, when there is a cell 11 with an excessively low SOC, it becomes impossible to discharge even if other cells 11 have discharge capacity. Therefore, by making the charge redistribution as described above possible, it is possible to maintain the discharged state of the battery as much as possible by using other cells 11 that have discharge capacity.

In step S7 following the cell temperature prediction step, it is determined whether the driving switch 49 of the vehicle 1 is on. When the operation switch 49 is on, the process proceeds to step S8, where it is determined whether the predicted temperature of the battery module M exceeds a predetermined value Tbd (45° C.). When the predicted temperature of the battery module M is below the predetermined value Tbd, the process proceeds to step S9, where it is determined whether there is a high temperature cell 11 whose predicted temperature exceeds the predetermined value Tcd (45° C.).

If there is a high-temperature cell 11, the process advances to step S10, and it is determined whether or not rapid cooling of the high-temperature cell 11 is necessary. When rapid cooling is required, the process proceeds to step S11, and the high SOC cells 11 are placed on both sides of the cell 11 so that heat is transferred from the high temperature cell 11 to the low temperature cells 11 on both sides of which the temperature is relatively low. A process of energizing the Peltier element 12 is executed.

That is, in the balancing/heat transfer circuit 40 shown in FIG. 4, the primary coil 43a of the transformer 43 is connected to the high SOC cell 11 by the primary coil switching circuit 44, and the secondary coil 43b of the transformer 43 is connected to the high SOC cell 11 by the changeover switch SW3. It is connected to the moving circuit 42 and performs on/off control of the primary coil switches SW1 and SW2. As a result, as shown in FIG. 5, surplus power from the high SOC cell 11 is energized to the Peltier elements 12 on both sides of the high temperature cell 11 via the transformer 43 of the balancing/heat transfer circuit 40. This energization is carried out for a time necessary for the predicted temperature of the cell 11 to fall below the predetermined value Tcd.

After the Peltier element 12 is energized for the required time, the process proceeds from step S11 to step S12, where cell balance processing is executed. That is, in the balancing/heat transfer circuit 40 shown in FIG. 4, the primary coil 43a of the transformer 43 is connected to the high SOC cell 11 by the primary coil switching circuit 44, and the secondary coil 43b of the transformer 43 is connected to the changeover switch. It is connected to the cell balancing circuit 41 by SW3, and performs on/off control of the primary coil switches SW1 and SW2. As a result, as shown in FIG. 5, the remaining surplus power is transferred from the previous high SOC cell 11 to the other low SOC cells 11 through the transformer 43 of the balancing/heat transfer circuit 40 to each cell of the battery module M. will be redistributed to 11.

On the other hand, if the cell 11 does not require rapid cooling, the process advances from step S10 to step S13. In step S13, the cell 11 whose temperature is lower exists through the transformer 43 due to surplus power from the high SOC cell 11 so that heat is transferred to the cell 11 whose temperature is lower among the cells 11 on both sides of the cell 11. A process of energizing the Peltier element 12 on one side is executed. This energization is carried out for a time necessary for the predicted temperature of the cell 11 to drop below the predetermined value Tcd. Thereafter, the process proceeds to step S12, where a cell balancing process is executed to redistribute the remaining surplus power from the high SOC cell 11 to each cell 11 of the battery module M via the transformer 43 of the balancing/heat transfer circuit 40. Ru.

When it is determined in step S7 that the operation switch 49 of the vehicle 1 is off, the process proceeds to step S14, where it is determined whether the predicted temperature of the battery module M exceeds a predetermined value Tbs (55° C.). When the predicted temperature of the battery module M is below the predetermined value Tbs, the process proceeds to step S15, where it is determined whether there is a high temperature cell 11 whose predicted temperature exceeds the predetermined value Tcs (55° C.).

When there is a high temperature cell 11, it is determined whether or not rapid cooling of the high temperature cell 11 is necessary, in the same way as when the operation switch 49 of the vehicle 1 described above is on. When rapid cooling is not required, the Peltier element 12 is energized so that the heat is transferred from the high SOC cell 11 to the low temperature cell 11 on one side of the high SOC cell 11. , cell balance processing is executed (steps S10 to S13).

In each of steps S9 and S15, if it is determined that there is no high temperature cell 11 whose predicted temperature exceeds the predetermined value Tcd (or Tcs), the process proceeds to step S12 without executing the heat transfer process by the Peltier element 12. Then, cell balance processing is executed.

In each of steps S8 and S14, when it is determined that the predicted temperature of the battery module M exceeds the predetermined value bd (or Tbs), the process proceeds to step S16, and a cooling fan is installed so that the battery module M is cooled. 65 is turned on (fan operation and shutter opening), or when the cooling fan 65 is already operating, the air volume is increased.

As described above, according to the above control, since power is supplied from the high SOC cell 11 only to the Peltier element 12 that cools the high temperature cell 11 exceeding the threshold value, the high temperature cell 11 is cooled with less power and the battery life is extended. be able to. After cooling the high-temperature cell, the charge of the high-SOC cell is redistributed to each cell, and this cell balance can increase the effective capacity of the battery. Here, the energization to the Peltier element serves as passive balancing, and the redistribution of the charge serves as active balancing. In other words, cell balance is performed by both of them.

Further, according to the above control, the temperature threshold for cooling the cell 11 by the Peltier element 12 differs depending on whether the operation switch 49 of the vehicle 1 is on or off, and when it is on, the threshold is lower than when it is off. . That is, when the temperature of the cell 11 increases while the vehicle is running, the cooling process is performed early. Therefore, when the load on the battery increases due to accelerated driving of the vehicle, etc., it is possible to prevent the cell 11 from deteriorating due to excessive temperature rise. On the other hand, when the vehicle 1 is not running, the temperature threshold is high, so power consumption for cooling the cells 11 can be suppressed.

Further, according to the above control, when the degree of cooling demand of the cell 11 is high, heat is transferred from the high temperature cell 11 to the cells 11 on both sides thereof, so that the cell 11 can be rapidly cooled. When the cooling requirement is low, heat is transferred to the low temperature cell 11 with a lower temperature among the low temperature cells 11 on both sides of the high temperature cell 11. In other words, the Peltier element 12 is used between cells with a large temperature difference. Since heat transfer is performed, cooling efficiency is increased.

<Others>
In the above embodiment, the cell 11 that is the power (charge) supply source in heat transfer and cell balance is specified based on the SOC, but it is specified based on the cell voltage (the cell with the highest voltage is the power supply source). ) may be done.

In the above embodiment, power is transferred from the cell 11 serving as the power supply source using the transformer 43, but the power may be transferred using a capacitor.

In the above embodiment, when the temperature of the high SOC cell 11 is below a predetermined value, cooling of the cell 11 and cell balancing by the Peltier element 12 is prohibited, but even when the temperature of the low SOC cell 11 is low, the cell Balancing may be prohibited (cooling of the cell 11 by the Peltier element 12 is performed).

1 Vehicle 2 Engine 4 Battery 11 Cell 12 Peltier element 30 Motor 40 Balancing/heat transfer circuit 41 Cell balancing circuit 42 Heat transfer circuit 64 Controller

Claims (12)

A method for controlling a battery formed by connecting a plurality of chargeable and dischargeable cells arranged in parallel in series,
A Peltier element is provided between adjacent cells of the plurality of cells, which transfers heat from one cell to the other cell by energization,
Detecting the SOC or voltage of each of the plurality of cells;
detecting the temperature of each of the plurality of cells;
When there are variations in the SOC or voltage of the plurality of cells and there is a high temperature cell among the plurality of cells whose temperature exceeds a predetermined threshold, a low temperature cell whose temperature is relatively low next to the high temperature cell energizing the Peltier element between the high temperature cell and the low temperature cell from the cell with the highest SOC or voltage to transfer heat to;
A method for controlling a battery, comprising the step of, after the step of energizing the Peltier element, redistributing the charge of the cell with the highest SOC or voltage to each cell of the battery. In claim 1,
In the step of detecting the temperature of each of the plurality of cells, the temperature of each cell is detected by the sensor, and the amount of temperature increase expected to increase due to the heat generation of each cell when the charge is redistributed is added to the detected temperature. A battery control method characterized by determining the temperature of each cell by taking into account the following. In claim 1 or claim 2,
A method for controlling a battery, characterized in that when the temperature of the cell with the highest SOC or voltage is below a predetermined value, conduction of current from the cell to the Peltier element and redistribution of the charge are prohibited. In claim 3,
Prohibition of energization of the Peltier device and redistribution of the charge is prohibited when the SOC or voltage of the cell with the highest SOC or voltage is below a predetermined value, and the SOC or voltage of the cell with the lowest SOC or voltage is prohibited. A method for controlling a battery, characterized in that the condition is that the value is greater than or equal to a predetermined value. In any one of claims 1 to 4,
The above battery is used to supply power to the motor that drives the vehicle,
The threshold value related to the cell temperature when the switch for operating and stopping the power train including the motor of the vehicle is off and on is different, and the threshold value is on when it is off. A method for controlling a battery, characterized in that the voltage is higher than a threshold value when In any one of claims 1 to 5,
a step of determining whether the cooling requirement of the high temperature cell is high or low based on the temperature of the high temperature cell;
When the degree of cooling demand is high, electricity is applied to each of the low-temperature cells on both sides of the high-temperature cell and the Peltier element between the high-temperature cells, and when the degree of cooling demand is low, the low-temperature cells on both sides of the high-temperature cell are energized. A method for controlling a battery, comprising energizing the Peltier element between the low-temperature cell whose temperature is lower and the high-temperature cell. A battery control device comprising a plurality of parallelly arranged chargeable and dischargeable cells connected in series,
a Peltier element that is provided between adjacent cells of the plurality of cells and that transfers heat from one cell to the other cell when energized;
A cell balancing circuit that redistributes the charge of the cell with the highest SOC or voltage among the plurality of cells to each cell of the battery;
A heat transfer circuit that causes the charge of the cell with the highest SOC or voltage among the plurality of cells to flow through the Peltier element to transfer the heat;
The SOC or voltage and temperature of each of the plurality of cells are detected, and when there are variations in the SOC or voltage of the plurality of cells and there is a high temperature cell among the plurality of cells whose temperature exceeds a predetermined threshold. , the heat is transferred between the cell with the highest SOC or voltage and the Peltier element so that heat is transferred from the high temperature cell to the adjacent low temperature cell whose temperature is relatively low via the Peltier element between both cells. a controller that connects the cell with the highest SOC or voltage to the cell balancing circuit so that the charge redistribution occurs after performing the process of lowering the temperature of the high temperature cell; A battery control device comprising: In claim 7,
The temperature of each of the plurality of cells is determined by adding to the temperature detected by the sensor an amount of temperature increase that is expected to increase due to heat generation in each cell when the charge is redistributed. control device. In claim 7 or claim 8,
The controller is a battery control device characterized in that, when the temperature of the cell with the highest SOC or voltage is below a predetermined value, conduction of electricity from the cell to the Peltier element and redistribution of the charge are prohibited. . In claim 9,
Prohibition of energization of the Peltier device and redistribution of the charge is prohibited when the SOC or voltage of the cell with the highest SOC or voltage is below a predetermined value, and the SOC or voltage of the cell with the lowest SOC or voltage is prohibited. 1. A battery control device, characterized in that the condition is that is equal to or higher than a predetermined value. In any one of claims 7 to 10,
The above battery is a battery that supplies power to the motor that drives the vehicle,
The threshold value related to the cell temperature when the switch for operating and stopping the power train including the motor of the vehicle is off and on is different, and the threshold value is on when it is off. A battery control device characterized in that the battery voltage is higher than the threshold value of the battery. In any one of claims 7 to 11,
The controller determines whether the degree of cooling demand of the cell is high or low based on the temperature of the high temperature cell, and when the degree of cooling demand is high, the controller determines whether the degree of cooling demand of the cell is high or low, and when the degree of cooling demand is high, the controller is configured to connect each of the low temperature cells on both sides of the high temperature cell to the high temperature cell. When the degree of cooling demand is low, the Peltier element between the low-temperature cell having a lower temperature among the low-temperature cells on both sides of the high-temperature cell and the high-temperature cell is energized. Characteristic battery control device.

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