JP2018147804A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit, in a battery pack comprising a plurality of battery modules connected in parallel with each other, large reflux current from flowing between battery modules when after a battery module returned into a normal state is reconnected to another battery module power supply to a battery included in each battery module is tried to be stopped.SOLUTION: When after a battery module 2 returned into a normal state is reconnected to another battery module 2 power supply to a battery B included in each battery module 2 is tried to be stopped, the battery module 2 returned into the normal state is separated from the other battery module 2 and power supply to a battery B included in the other battery module 2 is stopped in the case that a difference ΔOCV between an open circuit voltage OCVr of a battery B included in the battery module 2 returned into the normal state and an open circuit voltage OCVo of the battery B included in the other battery module 2 is equal to or larger than a threshold Vth.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a battery pack.

  As an existing battery pack, it has multiple battery modules connected in parallel to each other, and if one of the battery modules becomes abnormal, disconnect the abnormal battery module from the other battery modules. Some other battery modules continue to supply power to the load.

  In the battery pack configured as described above, when the voltage difference between the battery modules increases, the reflux current flowing between the battery modules also increases as the voltage difference increases. Therefore, when a battery module that has become abnormal returns to normal, and when the battery module that has returned to normal is reconnected to another battery module, a reflux current greater than the rated current of the fuse or battery continues to flow to the battery module, There is a risk that the fuse may blow 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 the other battery module, the voltage of the battery that the battery module has returned to normal and the voltage of the battery that the other battery module has. It is conceivable that the battery modules that have returned to normal are reconnected to other battery modules when and become the same voltage or substantially the same voltage.

  As related technologies, there are, for example, Patent Document 1 and Patent Document 2.

JP 2009-212020 A JP 2014-187807 A

  However, while recharging the batteries of other battery modules, after reconnecting the battery modules that have returned to normal to the other battery modules, charging of the batteries of each battery module is completed, and current flows to each battery. If there is no battery, the voltage of each battery fluctuates according to the current flowing in the battery and the internal resistance of the battery, so that the voltage after the fluctuation of the battery that the battery module has returned to normal and the battery that the other battery module has There is a possibility that the reflux current may flow between the battery module that has returned to normal and another battery module. Further, if the return current is larger than the rated current of the fuse or battery, the fuse may be blown or the battery may be deteriorated.

  Accordingly, an object according to one aspect of the present invention is to provide a battery pack including a plurality of battery modules connected in parallel to each other, and after reconnecting a battery module that has returned to normal to another battery module, each battery module has a battery. When stopping the power supply to the battery module, it is possible to prevent a large return current from flowing between the battery modules.

A battery pack according to one embodiment 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 to each other.

  A control part isolate | separates the battery module which became abnormal from another battery module by interrupting | blocking the switch which the battery module which became abnormal out of several battery modules.

  In addition, the control unit returns to the normal state after the battery module that has become abnormal returns to normal during charging of the battery of the other battery module, reconnects the battery module that has returned to normal to the other battery module, and then returns to normal. When trying to stop the power supply to the battery that the other battery module has and the battery that the other battery module has, the charging rate of the battery that the battery module has returned to normal and the charging rate of the battery that the other battery module has Estimating the open circuit voltage of the battery that the battery module that has returned to normal and the open circuit voltage of the battery that the other battery module has, and the open circuit voltage of the battery that the battery module that has returned to normal and the battery that the other battery module has When the difference from the open circuit voltage of the battery is above the threshold, the battery module that has returned to normal is disconnected from the other battery modules. Stopping electric power supply to the battery having other battery modules.

  According to the present invention, in a battery pack including a plurality of battery modules connected in parallel to each other, after the battery modules that have returned to normal are reconnected to other battery modules, power supply to the batteries of each battery module is stopped. When trying to make it, it can suppress that a big return current flows between battery modules.

It is a figure which shows an example of the battery pack of embodiment. It is a flowchart which shows an example of operation | movement of a control part. It is a figure which shows an example of the voltage change of the battery in charge and an example of a SOC-OCV curve. It is a flowchart which shows the other example of operation | movement of a control part.

Hereinafter, embodiments will be described in detail with reference to the drawings.
Drawing 1 is a figure showing an example of a battery pack of an embodiment.
A battery pack 1 shown in FIG. 1 is mounted on a vehicle such as an electric forklift 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. Main switch SWm, storage unit 3, and control unit 4.

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, respectively.
The battery B is composed of a plurality of secondary batteries (for example, a lithium ion battery, a nickel metal hydride battery, or an electric double layer capacitor) connected in series. Note that the battery B may be configured by one secondary battery.

  The switch SW is configured by, 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 another battery module 2 that 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 another battery module 2 in which the switch SW is conductive.

  The fuse HU is connected in series to the switch SW. When the fuse HU is blown by a large current exceeding the rated current of the fuse HU flowing through the battery module 2 continuously for a predetermined time or longer, the battery module 2 is disconnected 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 a current flowing through the battery B, the switch SW, and the fuse HU.
The temperature detection unit 22 is constituted by, for example, a thermistor, and detects the temperature of the battery B or the ambient temperature of the battery B.

  The monitoring unit 23 is configured by an IC (Integrated Circuit), for example, and detects the voltage of the battery B. Further, the monitoring unit 23 controls conduction or blocking of the switch SW according to an instruction sent from the control unit 4. In addition, the monitoring unit 23 sends 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 configured by, for example, a semiconductor relay such as a MOSFET or an electromagnetic relay.
When the main switch SWm is turned on, the battery B and the charger Ch included in the battery module 2 in which the switch SW is turned on 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 power is being supplied from the charger Ch to the battery pack 1 or when regenerative power is being supplied from the load Lo (not shown) to the battery pack 1, The battery B included in the battery module 2 in which the switch SW is conducted is charged, and the voltage of the battery B increases.

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

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

  In addition, when at least one of the voltage, current, and temperature indicated in the battery state information is equal to or higher than the abnormality threshold, 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 state information are all smaller than the abnormal threshold, it is determined that the battery module 2 that is the source of the battery state information is normal.

Further, the control unit 4 disconnects the battery module 2 from the other battery modules 2 by blocking the switch SW of the battery module 2 that has become abnormal.
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 a charging start instruction sent from the charger Ch (S21: Yes), the charging of the battery B is performed. Control is started (S22).

  For example, the control unit 4 sends a current command value whose upper limit is the current value sent from the charger Ch to the charger Ch, and controls the electric power supplied from the charger Ch to the battery B, whereby the battery B Charge control.

Next, if the control part 4 judges that charge of the battery pack 1 was complete | finished (S23: Yes), it will stop the electric power supply to the battery B (S24).
For example, when the charging rate of the battery B reaches the target value set by the user or the like, the control unit 4 receives the charging end instruction sent from the charger Ch, or the charging plug Pg is set by the user. By detecting that the battery pack 1 is pulled out from the connector Co, it is determined that the charging of the battery B is completed.

  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 cutting off the main switch SWm. That is, charging to 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 battery module 2 that has become abnormal returns to normal, and the voltage of the battery B (closed circuit voltage CCVo) of the other battery module 2 returns to the voltage of the battery B (open circuit) of the battery module 2 that has returned to normal. When the voltage is equal to or substantially the same as the voltage OCVr (S25: Yes and S26: Yes), the battery module 2 that has returned to normal is turned on by switching on the switch SW of the battery module 2 that has returned to normal. 2 is reconnected (S28).

Note that, when there are a plurality of other battery modules 2, the closed circuit voltage CCVo is an average voltage of the closed circuit voltages CCVo of the batteries B included in the other battery modules 2.
In addition, after the battery module 2 that has become abnormal returns to normal (S25: Yes), the control unit 4 determines that the battery B has 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 included in the other battery module 2 is stopped (S24).

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

  For example, the control unit 4 sets the integrated value of the current flowing through the battery B of the battery module 2 that has returned to normal from the time of reconnection until the end of charging of the battery pack 1 as the current integrated value ΔIr [Ah], In S30, SOC [%] = ((capacity [Ah] at the start of charging of battery B of battery module 2 returned to normal + current integrated value ΔIr [Ah]) / full charge capacity [Ah] of battery B) X100 is calculated, and the calculation result is defined as the charge rate SOCr of the battery B of the battery module 2 that has returned to normal.

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

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

  In S30, the control unit 4 refers to the SOC-OCV curve indicating the correspondence between the charging rate of the battery B and the open circuit voltage shown in FIG. The open circuit voltage corresponding to the charging rate 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 determines 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 the other battery modules 2. (S31), and if the difference ΔOCV is equal to or greater than the threshold value Vth (S32: Yes), the power supply to the battery B of the battery module 2 that has returned to normal and the battery B of the other battery module 2 is stopped. After that (S33), the battery module 2 that has returned to normal is disconnected from the other battery modules 2 (S34).

  The threshold value Vth is, for example, threshold value Vth = (current flowing to the battery B when the fuse HU may be blown or current flowing to the battery B when the battery B may be deteriorated) × (normally You may obtain | require by calculating the combined resistance of the internal resistance of the battery B which the returned battery module 2 has, and the battery B which the other battery module 2 has.

  On the other hand, when the difference ΔOCV is smaller than the threshold value Vth (S32: No), the control unit 4 stops 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. (S24), the battery module 2 that has returned to normal is not disconnected from the other battery modules 2.

  In the example of the operation of the control unit 4 shown in FIG. 2, when the difference ΔOCV is equal to or greater than the threshold value Vth (S32: Yes), the battery B included in the battery module 2 that has returned to normal and the battery included in the other battery module 2 are included. After stopping the power supply to B (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. When the difference ΔOCV is equal to or greater than the threshold value Vth (S32: Yes), the battery module 2 that has returned to normal is disconnected from the other battery module 2 (S34), and then the battery B included in the other battery module 2 is transferred. The power supply may be stopped (S33).

Thus, by replacing S33 and S34, the time during which the reflux 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 charging will be ended. For example, the case where the charge stop button of a charger was pushed by the user is assumed. In that case, the control unit 4 receives a charge end instruction from the charger Ch, and determines that the charge is ended.

  Moreover, the operation | movement which stops the electric power supply of step S24, S33 may be abbreviate | omitted by being included in step S23, S27, or S29. That is, even in this case, when the difference ΔOCV is equal to or greater than the threshold value Vth, the battery module 2 that has returned to normal is disconnected from the other battery module 2 and power is supplied to the battery B of the other battery module 2. Can be stopped.

  Here, for example, as shown in FIG. 3B, when the battery pack 1 is started to be charged (time t0), the open circuit voltage OCVr of the battery B of the battery module 2 that has returned to normal is changed to other battery modules. 2 is assumed to be larger than the closed circuit voltage CCVo of the battery B of the battery B.

  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 normal to the other battery module 2.

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

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

  Thereby, after the battery module 2 that has returned to normal is reconnected to the other battery module 2, the power supply to each battery B is stopped, and depending on the current flowing in the battery B and the internal resistance of the battery B Even if the voltage of each battery B fluctuates and the open circuit voltage OCVr and the open circuit voltage OCVo differ from each other, if the difference ΔOCV between the open circuit voltage OCVr and the open circuit voltage OCVo is greater than or equal to the threshold value Vth, it returns to normal. Since the battery module 2 can be disconnected from the other battery modules 2, a reflux current larger than the rated current of the fuse HU or the battery B flows between the battery module 2 and the other battery modules 2 that have returned to normal. This can be prevented.

  Further, when the difference ΔOCV is smaller than the threshold value Vth, a return current corresponding to the difference ΔOCV flows between the battery module 2 that has returned to normal and the other battery modules 2, and the return current is used as the fuse HU or the battery B. Can be made smaller than the rated current.

  That is, according to the battery pack 1 of the embodiment, it is possible to suppress a large reflux current from flowing between the battery modules 2, and thus it is possible to suppress the fuse HU from being blown or the battery B from being deteriorated. .

Further, the battery pack 1 of the embodiment has a configuration in which the battery module 2 that has returned to normal is not separated from the other battery modules 2 when the difference ΔOCV is smaller than the threshold value Vth.
Thereby, the opportunity to increase the capacity | capacitance of the battery pack 1 whole can be increased during charge of the battery pack 1. FIG.

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

DESCRIPTION OF SYMBOLS 1 Battery pack 2 Battery module 3 Memory | storage part 4 Control part 21 Current detection part 22 Temperature detection part 23 Monitoring part Ch Battery charger B Battery SW Switch SWm Main switch HU Fuse

Claims (2)

A plurality of battery modules each having a battery and a switch connected in series, and connected in parallel to each other;
A control unit that disconnects the abnormal battery module from other battery modules by shutting off a switch of the abnormal battery module among the plurality of battery modules;
With
The control unit, while charging the battery of the other battery module, the abnormal battery module returns normally, and after reconnecting the battery module returned to normal to the other battery module, When trying to stop the power supply to the battery of the battery module returned to normal and the battery of the other battery module, the charging rate of the battery of the battery module returned to normal and the other battery module Estimating the open circuit voltage of the battery included in the battery module returned to normal and the open circuit voltage of the battery included in the other battery module from the charge rate of the battery having When the difference between the voltage and the open circuit voltage of the battery of the other battery module is equal to or greater than a threshold value, the battery module that has returned to normal is returned. With disconnecting Lumpur from the other battery modules, battery pack, characterized in that to stop the power supply to a battery the other battery modules have. The battery pack according to claim 1,
When the difference is smaller than the threshold, the control unit does not disconnect the battery module that has returned to normal from the other battery module.

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