JP6733581B2 - Battery pack - Google Patents

Description

The present invention relates to a battery pack.

As an existing battery pack, it is equipped with multiple battery modules that are connected in parallel with each other, and if one of the multiple battery modules becomes abnormal, disconnect the abnormal battery module from other battery modules. In some cases, the power supply to the load is continued only by the other battery module.

In the battery pack configured as described above, when the voltage difference between the battery modules increases, the return current flowing between the battery modules also increases as the voltage difference increases. Therefore, when the abnormal battery module returns to normal and the battery module that has returned to normal is reconnected to another battery module, if a reflux current larger than the rated current of the fuse or the battery continues to flow to the battery module, The fuse may blow out or the battery may deteriorate.

Therefore, in order to suppress the return current corresponding to the voltage difference between the battery module that has returned to normal and another battery module, the voltage of the battery that the battery module that has returned to normal and the voltage of the battery that another battery module has When and become the same voltage or substantially the same voltage, it is conceivable to reconnect the battery module that has returned to normal to another battery module.

Related techniques include, for example, Patent Document 1 and Patent Document 2.

JP, 2009-212020, A JP, 2014-187807, A

However, while the battery of another battery module is being charged, after reconnecting the battery module that has returned to normal to the other battery module, charging of the battery of each battery module ends, and current flows to each battery. If it disappears, the voltage of each battery fluctuates according to the current flowing in the battery and the internal resistance of the battery, and the voltage of the battery that has returned to normal after the fluctuation of the battery and the battery of another battery module And the voltage after the fluctuation of the battery module are different from each other, and a return current may flow between the battery module that has returned to normal and another battery module. If the return current is larger than the rated current of the fuse or the battery, the fuse may be blown or the battery may deteriorate.

Therefore, an object according to one aspect of the present invention is that in a battery pack including a plurality of battery modules connected in parallel with each other, after reconnecting a battery module that has returned to normal operation to another battery module, a battery included in each battery module is provided. This is to prevent a large reflux current from flowing between the battery modules when trying to stop the power supply to the battery module.

A battery pack, which is one mode of the present invention, includes a plurality of battery modules and a control unit.
Each of the plurality of battery modules has a battery and a switch connected in series, and is connected in parallel with each other.

The control unit disconnects the abnormal battery module from the other battery modules by cutting off the switch of the abnormal battery module among the plurality of battery modules.

Further, the control unit controls the abnormal battery module to return to normal while charging the battery of the other battery module, reconnects the battery module returned to normal to the other battery module, and then returns to normal. When attempting to stop the power supply to the battery of the battery module and the battery of the other battery module, the battery charging rate of the battery module returned to normal and the charging rate of the battery of the other battery module are The open circuit voltage of the battery of the battery module that has returned to normal and the open circuit voltage of the battery of another battery module are estimated, and the open circuit voltage of the battery of the battery module that returns to normal and the battery of the other battery module If the difference from the open circuit voltage is equal to or more than the threshold value, the battery module that has returned to the normal state is separated from the other battery module, and the power supply to the battery of the other battery module is stopped.

According to the present invention, in a battery pack including a plurality of battery modules connected in parallel with each other, after reconnecting a battery module that has returned to a normal state to another battery module, the power supply to the battery of each battery module is stopped. When trying to do so, it is possible to prevent a large reflux current from flowing between the battery modules.

It is a figure which shows an example of the battery pack of embodiment. It is a flow chart which shows an example of operation of a control part. It is a figure which shows an example of a SOC-OCV curve and the example of a voltage change of the battery under charge. It is a flow chart which shows other examples of operation of a control part.

Embodiments will be described below in detail with reference to the drawings.
FIG. 1 is a diagram showing an example of the battery pack of the embodiment.
The battery pack 1 shown in FIG. 1 is provided, for example, in a vehicle such as an electric forklift truck or a plug-in hybrid car, and is provided between a plurality of battery modules 2 connected in parallel to each other and between each battery module 2 and a charger Ch. The main switch SWm, the storage unit 3, and the control unit 4 are provided.

Each battery module 2 includes a battery B, a switch SW, a fuse HU, a current detection unit 21, a temperature detection unit 22, and a monitoring unit 23.
The battery B is composed of a plurality of secondary batteries connected in series (for example, a lithium ion battery, a nickel hydrogen battery, or an electric double layer capacitor). The battery B may be composed of one secondary battery.

The switch SW is composed of, for example, a semiconductor relay such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an electromagnetic relay, and is connected to the battery B in series.

When the switch SW is turned on, the battery B of the battery module 2 having the switch SW is connected in parallel with the battery B of the other battery module 2 to which the switch SW is turned on.
When the switch SW is cut off, the battery B of the battery module 2 having the switch SW is disconnected from the battery B of the other battery module 2 to which the switch SW is conducting.

The fuse HU is connected in series with the switch SW. When a large current exceeding the rated current of the fuse HU flows into the battery module 2 for a predetermined time or more and the fuse HU is blown, the battery module 2 is separated from the other battery modules 2. In the example shown in FIG. 1, the switch SW and the fuse HU are connected to the negative terminal side of the battery B, but the switch SW and the fuse HU may be connected to the positive terminal side of the battery B.

The current detection unit 21 includes, for example, a Hall element or a shunt resistor, and detects the current flowing through the battery B, the switch SW, and the fuse HU.
The temperature detection unit 22 is composed of, for example, a thermistor, and detects the temperature of the battery B or the ambient temperature of the battery B.

The monitoring unit 23 includes, for example, an IC (Integrated Circuit), and detects the voltage of the battery B. Further, the monitoring unit 23 controls conduction or interruption of the switch SW according to an instruction sent from the control unit 4. Further, the monitoring unit 23 sends the battery state information indicating the voltage of the battery B, the current detected by the current detection unit 21, and the temperature detected by the temperature detection unit 22 to the control unit 4.

The main switch SWm is composed of, for example, a semiconductor relay such as MOSFET or an electromagnetic relay.
When the main switch SWm conducts, the battery B and the charger Ch included in the battery module 2 in which the switch SW conducts are connected to each other.

When the main switch SWm is cut off, the battery B included in the battery module 2 in which the switch SW is conductive is disconnected from the charger Ch.
When the main switch SWm is conducting and when electric power is being supplied from the charger Ch to the battery pack 1 or when regenerative electric power is being supplied to the battery pack 1 from a load Lo (not shown), The battery B included in the battery module 2 in which the switch SW is conductive is charged, and the voltage of the battery B rises.

Further, when the main switch SWm is conducting and when power is supplied from the battery pack 1 to the load Lo (not shown), the battery B of the battery module 2 with the switch SW conducting is discharged. , The voltage of the battery B drops.

The storage unit 3 is composed of, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory), and stores an SOC-OCV curve described later.
The control unit 4 is composed of, for example, a CPU (Central Processing Unit), a multi-core CPU, a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), etc.), and controls charging/discharging of the battery B.

Further, when at least one of the voltage, current, and temperature indicated in the battery state information is equal to or higher than the abnormal threshold value, the control unit 4 determines that the battery module 2 that is the source of the battery state information is abnormal. If the voltage, current, and temperature indicated in the battery status information are all smaller than the abnormal threshold value, it is determined that the battery module 2 that is the source of the battery status information is normal.

Further, the control unit 4 disconnects the battery module 2 from other battery modules 2 by cutting off the switch SW of the abnormal battery module 2.
FIG. 2 is a flowchart showing an example of the operation of the control unit 4.

First, when the control unit 4 detects that the charging plug Pg is connected to the connector Co of the battery pack 1 and receives the charge start instruction sent from the charger Ch (S21: Yes), the battery B is charged. Control is started (S22).

For example, the control unit 4 sends a current command value having an upper limit value of the current value sent from the charger Ch to the charger Ch to control the electric power supplied from the charger Ch to the battery B, so that the battery B Charge control.

Next, when the control unit 4 determines that the charging of the battery pack 1 is completed (S23: Yes), the power supply to the battery B is stopped (S24).
For example, when the charging rate of the battery B reaches a target value set by the user or the like, or the control unit 4 receives a charging end instruction sent from the charger Ch, or the user sets the charging plug Pg. By detecting that the battery pack 1 is pulled out from the connector Co, it is determined that the battery B has been charged.

Further, for example, the control unit 4 stops the power supply to the battery B by setting the current command value to be sent to the charger Ch to zero or by shutting off the main switch SWm. That is, the charging of the battery B is stopped.

On the other hand, when the control unit 4 determines that the charging of the battery pack 1 is not completed (S23:No and S25:No, or S23:No, S25:Yes, S26:No, and S27:No. ), the abnormal battery module 2 returns to normal, and the voltage of the battery B of another battery module 2 (closed circuit voltage CCVo) is the voltage of the battery B of the battery module 2 that returns to normal (open circuit). When the voltage becomes equal to or substantially the same as the voltage OCVr) (S25: Yes and S26: Yes), the switch SW included in the battery module 2 that has returned to the normal state is made conductive, so that the battery module 2 that has returned to the normal state is replaced with another battery module. 2 is reconnected (S28).

Note that the closed circuit voltage CCVo is the average voltage of the closed circuit voltage CCVo of the battery B of the other battery modules 2 when there are a plurality of other battery modules 2.
In addition, after the abnormal battery module 2 returns to the normal state (S25: Yes), the control unit 4 controls the battery B before the closed circuit voltage CCVo becomes the same or substantially the same voltage as the open circuit voltage OCVr. When it is determined that the charging is completed (S27: Yes), the power supply to the battery B of another battery module 2 is stopped (S24).

After reconnecting the battery module 2 that has returned to normal to another battery module 2 (S28), the control unit 4 returns to normal when it determines that charging of the battery pack 1 has ended (S29: Yes). The open circuit voltage OCVr of the battery B of the battery module 2 and the open circuit voltage OCVo of the battery B of the other battery module 2 are estimated (S30).

For example, the control unit 4 sets the integrated value of the current flowing in the battery B included in the battery module 2 that has returned to normal as the integrated current value ΔIr[Ah] from the time of reconnection to the end of charging of the battery pack 1, In S30, SOC [%]=((charge-starting capacity [Ah] of battery B of the battery module 2 returned to normal+current integrated value ΔIr[Ah])/full charge capacity of battery B [Ah]) ×100 is calculated, and the calculation result is set as the charging rate SOCr of the battery B included in the battery module 2 that has returned to normal.

Further, the control unit 4 calculates the integrated value of the currents flowing through the other battery modules 2 from the start of charging the battery B of the other battery module 2 to the end of the charging of the battery pack 1 as the current integrated value ΔIo[ Ah], and in S30, SOC [%]=((capacity [Ah] of another battery module 2 at the start of charging of battery B+current integrated value ΔIo[Ah])/full charge capacity of battery B [Ah] ])×100 is calculated, and the calculation result is used as the charging rate SOCo of the battery B of another battery module 2. For the charging rates SOCr and SOCo, the charging rate at the start of charging is obtained from the open circuit voltage at the start of charging, and SOC [%]=charging rate at the start of charging+(current integrated value [Ah]/full battery B The charge capacity [Ah])×100 may be calculated and obtained.

Further, in S30, the control unit 4 refers to the SOC-OCV curve showing the correspondence relationship between the charging rate of the battery B and the open circuit voltage shown in FIG. 3A, and the battery included in the battery module 2 that has returned to the normal state. The open circuit voltage corresponding to the state of charge SOCr of B is estimated as the open circuit voltage OCVr of the battery B of the battery module 2 that has returned to normal.

In S30, the control unit 4 refers to the SOC-OCV curve indicating the correspondence relationship between the charging rate of the battery B and the open circuit voltage shown in FIG. The open circuit voltage corresponding to the state of charge SOCo is estimated as the open circuit voltage OCVo of the battery B included in the other battery module 2.

Further, in the flowchart shown in FIG. 2, the control unit 4 causes the difference ΔOCV between the open circuit voltage OCVr of the battery B of the battery module 2 that has returned to normal and the open circuit voltage OCVo of the battery B of the other battery module 2. (S31), and if the difference ΔOCV is equal to or more than the threshold value Vth (S32: Yes), the power supply to the battery B included in the battery module 2 that has returned to normal and the battery B included in another battery module 2 is stopped. After that (S33), the battery module 2 that has returned to the normal state is separated from the other battery modules 2 (S34).

The threshold value Vth is, for example, threshold value Vth=(current flowing through the battery B when the fuse HU is likely to be blown, or current flowing through the battery B when the battery B is likely to deteriorate)×(normally It may be determined by calculating the combined resistance of the batteries B of the returned battery module 2 and the batteries B of the other battery modules 2.

On the other hand, when the difference ΔOCV is smaller than the threshold value Vth (S32: No), the control unit 4 stops the power supply to the battery B included in the battery module 2 that has returned to normal and the battery B included in the other battery module 2. After that (S24), the battery module 2 that has returned to the normal state is not separated from the other battery modules 2.

In the example of the operation of the control unit 4 illustrated in FIG. 2, when the difference ΔOCV is equal to or more than the threshold value Vth (S32: Yes), the battery B included in the battery module 2 that has returned to the normal state and the battery included in the other battery module 2 are included. After the power supply to B is stopped (S33), the battery module 2 that has returned to normal is disconnected from the other battery modules 2 (S34), but another example of the operation of the control unit 4 shown in FIG. As described above, when the difference ΔOCV is equal to or more than the threshold value Vth (S32: Yes), after the battery module 2 that has returned to the normal state is separated from the other battery module 2 (S34), the battery B included in the other battery module 2 is transferred. The power supply may be stopped (S33).

In this way, by replacing S33 and S34, the time during which the return current continues to flow can be further shortened.
Further, the determination of the end of charging in steps S23, S27, and S29 may be a case where it is determined that the charging is about to end. For example, it is assumed that the user has pressed the charge stop button of the charger. In that case, the control unit 4 receives the charging end instruction from the charger Ch and determines that the charging is ended.

The operation of stopping the power supply in steps S24 and S33 may be omitted because it is included in step S23, S27, or S29. That is, even in this case, when the difference ΔOCV is equal to or more than the threshold value Vth, the battery module 2 that has returned to the normal state is disconnected from the other battery module 2 and the power supply to the battery B included in the other battery module 2 is performed. It can be stopped.

Here, for example, as shown in FIG. 3B, at the start of charging the battery pack 1 (time t0), the open circuit voltage OCVr of the battery B of the battery module 2 that has returned to normal is different from that of another battery module. It is assumed that the voltage is higher than the closed circuit voltage CCVo of the battery B that 2 has.

First, when the closed circuit voltage CCVo becomes the same or substantially the same voltage as the open circuit voltage OCVr at time t1, the control unit 4 reconnects the battery module 2 that has returned to the normal state with another battery module 2.

After that, at time t2, the control unit 4 determines that the charging of the battery pack 1 is completed, and if the difference ΔOCV between the open circuit voltage OCVr and the open circuit voltage OCVo estimated at that time is equal to or more than the threshold value Vth, it is normal. The battery module 2 that has returned to 1 is disconnected from the other battery module 2, and at least the power supply to the battery B of the other battery module 2 is stopped.

As described above, in the battery pack 1 of the embodiment, the abnormal battery module 2 returns to the normal state while the battery B of the other battery module 2 is being charged, and the battery module 2 that has returned to the normal state is replaced with the other battery module 2. After reconnecting to the module 2, when the power supply to the battery B of the battery module 2 that has returned to normal and the battery B of another battery module 2 is stopped, the battery module 2 that has returned to normal has The open circuit voltage OCVr of the battery B of the battery module 2 returned to normal from the charge rate SOCr of the battery B and the charge rate SOCo of the battery B of the other battery module 2 and the open circuit of the battery B of the other battery module 2. When the voltage OCVo is estimated and the difference ΔOCV between the open circuit voltage OCVr of the battery B included in the battery module 2 that has returned to normal and the open circuit voltage OCVo of the battery B included in another battery module 2 is equal to or greater than the threshold value Vth, The battery module 2 that has returned to 1 is disconnected from the other battery module 2, and the power supply to the battery B of the other battery module 2 is stopped.

As a result, after the battery module 2 that has returned to the normal state is reconnected to another battery module 2, the power supply to each battery B is stopped, and the current flowing in the battery B and the internal resistance of the battery B are changed. Even if the voltage of each battery B fluctuates and the open circuit voltage OCVr and the open circuit voltage OCVo are different from each other, if the difference ΔOCV between the open circuit voltage OCVr and the open circuit voltage OCVo is equal to or more than the threshold value Vth, it returns to normal. Since the battery module 2 can be disconnected from the other battery module 2, a reflux current larger than the rated current of the fuse HU or the battery B flows between the battery module 2 that has returned to the normal state and the other battery module 2. It can be prevented.

Further, when the difference ΔOCV is smaller than the threshold value Vth, a return current according to the difference ΔOCV flows between the battery module 2 that has returned to the normal state and another battery module 2, and the return current flows through the fuse HU and the battery B. Can be smaller than the rated current of.

That is, according to the battery pack 1 of the embodiment, it is possible to prevent a large return current from flowing between the battery modules 2, so that it is possible to prevent the fuse HU from being blown and the battery B from being deteriorated. ..

Further, in the battery pack 1 of the embodiment, when the difference ΔOCV is smaller than the threshold value Vth, the battery module 2 that has returned to the normal state is not separated from the other battery modules 2.
This can increase the chances of increasing the capacity of the entire battery pack 1 while the battery pack 1 is being charged.

Further, the present invention is not limited to the above embodiment, and various improvements and changes can be made without departing from the gist of the present invention.

1 Battery Pack 2 Battery Module 3 Storage Unit 4 Control Unit 21 Current Detection Unit 22 Temperature Detection Unit 23 Monitoring Unit Ch Battery Charger B Battery SW Switch SWm Main Switch HU Fuse

Claims (2)

Each has a battery and a switch connected in series, and a plurality of battery modules connected in parallel with each other,
A control unit that disconnects the abnormal battery module from other battery modules by cutting off a switch of the abnormal battery module among the plurality of battery modules,
Equipped with
While the battery included in the other battery module is being charged, the control unit returns the abnormal battery module to the normal state, and reconnects the normal battery module to the other battery module, When attempting to stop the power supply to the battery included in the battery module that has returned to normal and the battery included in the other battery module, the charging rate of the battery included in the battery module that returned to normal and the other battery module are The open circuit voltage of the battery of the battery module that has returned to normal and the open circuit voltage of the battery of the other battery module are estimated from the charging rate of the battery that has, and the open circuit of the battery of the battery module that has returned to normal When the difference between the voltage and the open circuit voltage of the battery included in the other battery module is equal to or greater than a threshold value, the battery module that has returned to the normal state is separated from the other battery module, and the battery included in the other battery module is replaced. A battery pack characterized by stopping the power supply of. The battery pack according to claim 1, wherein
The battery pack, wherein the control unit does not separate the battery module that has returned to the normal state from the other battery module when the difference is smaller than the threshold value.

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