JP2016181991A - Charger and control method of charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charger which makes the actual battery voltage or capacity as evenly as possible, by executing cell balancing, even when high accuracy OCV cannot be acquired.SOLUTION: A charger includes a battery pack having a plurality of batteries B1-B4, a cell balance circuit for making the voltage or capacity of the batteries B1-B4 uniform, and a control circuit 1 for controlling the cell balance circuit. The control circuit 1 controls to perform cell balancing by using a first cell balance amount determined by the voltage difference of the batteries B1-B4, when a current is not flowing to the battery pack, or when a constant current is flowing to the battery pack, otherwise controls to execute cell balancing by using a second cell balance amount smaller than the first cell balance amount determined by the voltage difference of the batteries B1-B4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a charging device for controlling charging and a method for controlling the charging device.

  Conventionally, in cell balance that equalizes the voltage or capacity of each battery, a target value is obtained based on a measured open circuit voltage (OCV) or estimated OCV, and the target value is used. Cell balance processing is performed. Here, (1) the measured OCV is the OCV measured in a state where no current flows through the battery and the polarization is also eliminated. (2) The estimated OCV is an OCV estimated in a state where no current flows through the battery and in a state where polarization is not completely eliminated.

  However, when high-accuracy OCV (measured OCV or estimated OCV) cannot be obtained, the battery voltage or capacity cannot be detected accurately, and the target value used for the cell balance process cannot be obtained correctly. Then, since the cell balance process is performed for an incorrect target value, the voltages or capacities of the actual batteries cannot be equalized, and in some cases, the uniformity may be lost before the cell balance process is performed. In addition, if the cell balance process is not performed until the conditions ((1) and (2)) for obtaining the high-accuracy OCV are satisfied, in some cases, the actual voltage or capacity of the battery is excessively collapsed. This significantly reduces the battery usage range. Furthermore, when high-accuracy OCV cannot be obtained, the accuracy of full charge capacity estimation is deteriorated, and cell balance processing should be performed according to either a battery having a small capacity and a high voltage or a battery having a large capacity and a low voltage. Cannot be determined.

  As a related technique, when the control unit of the charging device or the power supply device has a difference between the maximum value and the minimum value of a plurality of battery voltages equal to or greater than a predetermined start threshold, the shunt circuit corresponding to the battery having the maximum voltage A technique is disclosed in which charging is performed while suppressing variation in voltage of each battery by starting a shunt operation and controlling the current flowing through the battery.

JP 2013-150440 A

  An object according to one aspect of the present invention is to provide a charging device and a method for controlling the charging device that make the actual battery voltages or capacities as equal as possible by performing cell balance processing even when highly accurate OCV cannot be obtained. Is to provide.

  A charging device according to one aspect of the present invention includes an assembled battery having a plurality of batteries, a cell balance circuit that equalizes the voltage or capacity of each battery, and a control circuit that controls the cell balance circuit. .

  When no current flows through the assembled battery or when a constant current flows through the assembled battery, the control circuit executes the cell balance processing using the first cell balance amount determined by the voltage difference between the batteries. Even when no current is flowing through the battery or when a constant current is flowing through the assembled battery, the cell balance is determined using a second cell balance amount smaller than the first cell balance amount determined by the voltage difference between the batteries. Perform balance processing.

  Even when a highly accurate OCV cannot be obtained, the actual battery voltage or capacity can be made as uniform as possible by executing the cell balance process.

FIG. 1 is a diagram illustrating an embodiment of a charging device. FIG. 2 is a flowchart showing an embodiment of the operation of the control circuit. FIG. 3 is a flow diagram illustrating one embodiment of the operation of methods 1 and 2. FIG. 4 is a flow diagram illustrating one embodiment of the operation of methods 3 and 4.

Hereinafter, embodiments will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating an embodiment of a charging device. 1 includes a battery pack having a plurality of batteries B1 to B4, a cell balance circuit that equalizes the voltages or capacities of the batteries B1 to B4, a control circuit 1 that controls the cell balance circuit, and a battery. Voltmeters 2a to 2d for measuring the voltages of B1 to B4, respectively. The charging device is mounted on a vehicle such as a hybrid vehicle, an electric vehicle, or a forklift.

  In the assembled battery, for example, a plurality of batteries B1 to B4 are connected in series. The assembled battery supplies power to supply power to the load. The load is, for example, a motor generator. The batteries B1 to B4 are, for example, lithium ion batteries, nickel metal hydride rechargeable batteries, capacitors, and the like. Further, the batteries B1 to B4 can be charged from an external power source.

  The cell balance circuit is a circuit that eliminates voltage variations between batteries as much as possible and equalizes them. In the example of FIG. 1, a passive cell balance circuit having voltmeters 2a to 2d, resistors R1 to R4, switches SW1 to SW5, and the like is shown. The passive cell balance circuit detects the battery with the lowest voltage among the assembled batteries, and performs the cell balance process so that the voltages of the other batteries are adjusted to this minimum value. Details of the passive cell balance circuit will be described later.

  When no current flows through the assembled battery (first condition) or when a constant current flows through the assembled battery (second condition), the control circuit 1 is based on the voltage difference between the batteries B1 to B4. The cell balance process is executed using the determined first cell balance amount. In addition, the control circuit 1 determines whether the first cell balance amount is determined based on the voltage difference between the batteries B1 to B4 when no current flows through the assembled battery or when a constant current flows through the assembled battery. The cell balance process is executed using a smaller second cell balance amount. The control circuit 1 is a battery ECU (Electronic Control Unit) or the like. The control circuit 1 may be a circuit having a CPU (Central Processing Unit) and a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), etc.). The operation of the control circuit 1 will be described later.

The cell balance circuit will be described.
In FIG. 1, an assembled battery having batteries B1 to B4 is shown for easy understanding. The batteries B1 to B4 are connected in series, a voltmeter 2a is connected between the positive terminal and the negative terminal of the battery B1, a voltmeter 2b is connected between the positive terminal and the negative terminal of the battery B2, and the battery B3 A voltmeter 2c is connected between the positive electrode terminal and the negative electrode terminal, and a voltmeter 2d is connected between the positive electrode terminal and the negative electrode terminal of the battery B4. The output terminals of the voltmeters 2 a to 2 d are connected to the input terminal of the control circuit 1 and send the measured voltage value to the control circuit 1.

  Further, one terminal of the switch SW1 is connected to the positive terminal of the battery B1, one terminal of the switch SW2 is connected to the negative terminal of the battery B1, and one terminal of the switch SW2 is connected to the positive terminal of the battery B2. One terminal of the switch SW3 is connected to the negative terminal of the battery B2, one terminal of the switch SW3 is connected to the positive terminal of the battery B3, and one terminal of the switch SW4 is connected to the negative terminal of the battery B3. Is connected, one terminal of the switch SW4 is connected to the positive terminal of the battery B4, and one terminal of the switch SW5 is connected to the negative terminal of the battery B4.

  One terminal of the resistor R1 is connected to the other terminal of the switch SW1, and the other terminal of the switch SW2 and one terminal of the resistor R2 are connected to the other terminal of the resistor R1. The other terminal of the switch SW3 and one terminal of the resistor R3 are connected to the other terminal of the resistor R2. The other terminal of the switch SW4 and one terminal of the resistor R4 are connected to the other terminal of the resistor R3. The other terminal of the switch SW5 is connected to the other terminal of the resistor R4.

  As the switches SW1 to SW5, for example, controllable switches such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and relays are conceivable. The resistors R1 to R4 are discharging resistors used to equalize the voltages or capacities of the batteries B1 to B4.

  For example, when the voltage of the battery B1 is the maximum voltage and the voltage of the battery B2 is the minimum voltage, the voltage difference between the voltage of the battery B1 and the voltage of the battery B2 is determined in advance to determine whether or not the uniformity is lost. When the voltage of the battery B1 is the same as the voltage of the battery B2 when the voltage is larger than the threshold value, the switch SW1 is turned on, the switches SW2 to SW5 are turned off, and power is consumed by the resistors R1 to R4. Thereafter, when the voltages of the batteries B1 and B2 are equal or in an equal range, the switch SW1 is turned off. The switches SW1 to SW5 are controlled by a control signal output from the control circuit 1 when performing cell balance processing. The passive cell balance circuit is not limited to the circuit shown in FIG. The cell balance circuit may be an active cell balance circuit or a progressive cell balance circuit.

The operation of the control circuit will be described.
FIG. 2 is a flowchart showing an embodiment of the operation of the control circuit. In step S1, the control circuit 1 determines whether no current is flowing through the assembled battery (first condition) or whether a constant current is flowing through the assembled battery (second condition). In Step S1, when it is determined that the first condition or the second condition is satisfied (Yes), the process proceeds to Step S2, and when there is neither the first condition nor the second condition (No). The process proceeds to step S6.

  The first condition, when no current flows through the assembled battery, is when the assembled battery is not charged or discharged, for example, a period from the completion of charging to the start of the next charging. In the period (period A) from the completion of charging to the elimination of polarization, the OCV is estimated based on the measured OCV, internal resistance, ambient environment, etc. of the batteries B1 to B4. Further, the measured OCV can be used in a period (period B) from when the polarization is eliminated until the next charging is started.

  When the constant current is flowing through the assembled battery, which is the second condition, the measured OCV of each of the batteries B1 to B4 is a period (period C) in which CC charging (Constant Current charging) is performed during charging. The OCV can be estimated based on the constant current flowing in the assembled battery, the internal resistance, the surrounding environment, and the like.

  In the first condition and the second condition, OCV estimation, full charge capacity estimation, usable capacity estimation, and chargeable capacity estimation can be performed with high accuracy, so that cell balance processing can be performed with high accuracy. it can.

In step S2, the control circuit 1 measures OCV or estimates OCV.
In the period A, the control circuit 1 estimates the OCV based on the OCV, internal resistance, ambient environment, and the like of the batteries B1 to B4. In the period B, the control circuit 1 measures OCV. In the period C, the control circuit 1 estimates the OCV based on the OCV of the batteries B1 to B4, the constant current flowing in the assembled battery, the internal resistance, the surrounding environment, and the like.

  In step S3, the control circuit 1 determines whether or not the uniformity has collapsed. If it has collapsed (Yes), the process proceeds to step 4. If it has not collapsed (No), the process proceeds to step 1.

  For example, in the determination of whether or not the uniformity in periods A and C is lost, the voltage difference between the maximum voltage and the minimum voltage of the estimated OCV for each of the batteries B1 to B4 is obtained, and the obtained voltage difference is lost. When it is equal to or greater than a predetermined threshold value for determining whether or not there is an equality, it is determined that the uniformity is lost. In the period B, for example, whether or not the uniformity is lost is determined by, for example, obtaining a voltage difference between the maximum voltage and the minimum voltage of the measured OCV for each of the batteries B1 to B4, and whether or not the obtained voltage difference is uneven. When it is equal to or greater than a threshold value determined in advance, it is determined that the uniformity is broken.

Note that the threshold value is a value for determining whether or not to execute the cell balance process, and may be determined by experiment or simulation, for example.
In step S4, the control circuit 1 calculates the first cell balance amount using the voltage difference between the batteries B1 to B4.

  In the case of the periods A and C, for example, the estimated OCV of each of the batteries B1 to B4 is OCV1 to OCV4, and the minimum voltage among the OCV1 to OCV4 is OCV4. The voltage difference between OCV1 and OCV4, the voltage difference between OCV2 and OCV4, and the voltage difference between OCV3 and OCV4 are obtained, and these voltage differences are used as the first cell balance amount.

  In the case of the period B, for example, the measured OCV of each of the batteries B1 to B4 is OCV1 to OCV4, and the minimum voltage among the OCV1 to OCV4 is OCV4. The voltage difference between OCV1 and OCV4, the voltage difference between OCV2 and OCV4, and the voltage difference between OCV3 and OCV4 are obtained, and these voltage differences are used as the first cell balance amount.

The first cell balance amount is not limited to the voltage difference, and may be a battery capacity difference or a time for executing the cell balance process.
In step S5, the control circuit 1 executes cell balance processing (high-accuracy cell balance processing) using the first cell balance amount.

  In the case of the passive cell balance circuit of FIG. 1, for example, if the maximum voltage of the batteries B1 to B4 is 4.0 [V], the minimum voltage is 3.5 [V], and the threshold is 0.4 V, the obtained voltage Since the difference 0.5 [V] is equal to or greater than the threshold value 0.4 [V], cell balance processing is executed, and the voltages of the batteries B1 to B4 are set to the minimum voltage 3.5 [V]. That is, a highly accurate cell balance process is performed to make it uniform or an equal range.

The cell balance process (steps S6 to S8, S5) when neither the first condition nor the second condition is present will be described.
In step S6, when it is determined that neither the first condition nor the second condition is found in step S1, the control circuit 1 measures the closed circuit voltage (CCV) or the measured CCV. The OCV is estimated based on the above, and the cell balance process is executed using any one of methods 1 to 4 described later. The methods 1 and 2 use the measured CCV, and the methods 3 and 4 execute the cell balance processing using the OCV estimated based on the measured CCV.

  In step S7, the control circuit 1 determines whether or not the equality is lost. If the equality is lost (Yes), the process proceeds to step 8. If the equality is not lost (No), the process proceeds to step 1. Transition. In step S8, the control circuit 1 calculates a second cell balance amount that is smaller than the first cell balance amount. Then, it transfers to step S5 and performs a cell balance process.

Details of steps S7 and S8 will be described.
(A) The determination as to whether or not the uniformity of the method 1 is broken is made, for example, when the voltage difference between the maximum voltage and the minimum voltage of the CCV measured for each of the batteries B1 to B4 is greater than or equal to the first threshold (in the method 1 Condition), it is determined that the uniformity is broken. The predetermined time T1 can be determined by experiment or simulation, for example. The first threshold value is a value for determining whether or not to execute the cell balance process, and may be determined by experiment or simulation, for example.

  The second cell balance amount of method 1 (<first cell balance amount) is the voltage difference when the voltage difference in CCV measured for each of batteries B1 to B4 is equal to or greater than the first threshold value under the conditions of method 1. Is used to determine the second cell balance amount. For example, it is conceivable that the predetermined voltage is subtracted from the voltage difference in CCV measured for each of the batteries B1 to B4 under the conditions of the method 1. When the predetermined voltage is α1 and the minimum voltage among CCV1 to CCV4 is CCV4, CCV1-CCV4-α1, CCV2-CCV4-α1, CCV3-CCV4-α1 are obtained and set as the second cell balance amount.

The predetermined voltage α1 is a value that makes the second cell balance amount smaller than the first cell balance amount, and a value that is determined in consideration of the measurement error of the CCV, and may be determined by experiment or simulation, for example.
(B) The determination as to whether or not the uniformity of the method 2 is broken is performed, for example, after the cell balance process (high-accuracy cell balance process) is performed using the first cell balance amount, and then a predetermined time T1 has elapsed. If the voltage difference between the maximum voltage and the minimum voltage of the CCV measured for each of the batteries B1 to B4 is equal to or greater than a second threshold value that is smaller than the first threshold value (condition of method 2), it is determined that the uniformity is lost. To do. The second threshold is a value for determining whether or not to execute the cell balance process, and may be determined by experiment or simulation, for example.

  The second cell balance amount of method 2 (<first cell balance amount) is equal to or greater than a second threshold value in which the voltage difference in CCV measured for each of batteries B1 to B4 under the condition of method 2 is smaller than the first threshold value. In this case, the second cell balance amount is determined using the voltage difference. For example, it can be considered that the predetermined voltage is subtracted from the voltage difference in CCV measured for each of the batteries B1 to B4 under the condition of the method 2. When the predetermined voltage is α2 and the minimum voltage among CCV1 to CCV4 is CCV4, CCV1-CCV4-α2, CCV2-CCV4-α2, CCV3-CCV4-α2 are obtained and set as the second cell balance amount.

The predetermined voltage α2 is a value that makes the second cell balance amount smaller than the first cell balance amount, and a value that is determined in consideration of the CCV measurement error, and may be determined by experiment or simulation, for example.
(C) The determination as to whether or not the uniformity of method 3 is lost is, for example, that the voltage difference between the maximum voltage and the minimum voltage of the OCV estimated using the measured CCV of each of the batteries B1 to B4 is greater than or equal to the third threshold value. In the case (condition of method 3), it is determined that the uniformity is broken. The estimated OCV is estimated using, for example, the measured CCV, the current flowing in the assembled battery, the amount of change in the current, the internal resistance, the battery and the ambient temperature of the battery, and the like. It is conceivable that the predetermined time T2 is determined by experiment or simulation, for example. The third threshold is a value for determining whether or not to execute the cell balance process, and may be determined by experiment or simulation, for example.

  The second cell balance amount of method 3 (<first cell balance amount) is such that the voltage difference in the OCV estimated using the measured CCV of each of batteries B1 to B4 under the conditions of method 3 is greater than or equal to the third threshold value. In this case, the second cell balance amount is determined using the voltage difference. For example, it is conceivable that the predetermined voltage is subtracted from the voltage difference in the OCV estimated using the CCV measured for each of the batteries B1 to B4 under the condition of the method 3. When the predetermined voltage is α3 and the minimum voltage among the estimated OCV1 to OCV4 is OCV4, OCV1-OCV4-α3, OCV2-OCV4-α3, OCV3-OCV4-α3 are obtained and the second cell balance amount is obtained. To do.

The predetermined voltage α3 is a value that makes the second cell balance amount smaller than the first cell balance amount, and is a value that is determined in consideration of an OCV estimation error, and may be determined by experiment or simulation, for example.
(D) The determination of whether or not the uniformity of the method 4 is broken is performed, for example, after the cell balance process (high-accuracy cell balance process) is performed using the first cell balance amount, and then a predetermined time T2 has elapsed. If the voltage difference between the maximum voltage and the minimum voltage of the OCV estimated using the measured CCV of each of the batteries B1 to B4 is equal to or greater than a fourth threshold value smaller than the third threshold value (condition of method 4), Is determined to have collapsed. The estimated OCV is estimated using, for example, the measured CCV, the current flowing in the assembled battery, the amount of change in the current, the internal resistance, the battery and the ambient temperature of the battery, and the like. The fourth threshold value is a value for determining whether or not to execute the cell balance process, and may be determined by experiment or simulation, for example.

  The second cell balance amount of method 4 (<first cell balance amount) is such that the voltage difference in the OCV estimated using the CCV measured for each of batteries B1 to B4 under the condition of method 4 is greater than the third threshold value. When the value is equal to or greater than the small fourth threshold value, the second cell balance amount is determined using the voltage difference. For example, it is conceivable that the predetermined voltage is subtracted from the voltage difference in the OCV estimated using the CCV measured for each of the batteries B1 to B4 under the condition of the method 4. When the predetermined voltage is α4 and the minimum voltage among the estimated OCV1 to OCV4 is OCV4, OCV1-OCV4-α4, OCV2-OCV4-α4, OCV3-OCV4-α4 are obtained and the second cell balance amount is obtained. To do.

  The predetermined voltage α4 is a value that makes the second cell balance amount smaller than the first cell balance amount, and a value that is determined in consideration of an OCV estimation error, and may be determined by experiment or simulation, for example.

In the methods 1 to 4, the second cell balance amount is not limited to the voltage difference, and may be a battery capacity difference or a time for executing the cell balance process.
Further, the accuracy of the acquired voltage is in the relationship of methods 1 and 2 <methods 3 and 4. That is, the relationship is as follows: measured CCV <OCV estimated based on CCV measured when current is flowing <measured OCV or estimated OCV.

Details of the processing in step S7 will be described.
FIG. 3 is a flow diagram illustrating one embodiment of the operation of methods 1 and 2. In step 301, the control circuit 1 performs cell balance processing (high-accuracy cell balance processing) with the first cell balance amount of method 1 or method 2, and determines whether or not a predetermined time T1 has elapsed, When the predetermined time T1 has elapsed (Yes), the process proceeds to step S303.

  In step 302, the control circuit 1 sets a threshold value for determining whether or not the uniformity is lost to the first threshold value (the threshold value of the method 1). When the predetermined time T1 has not elapsed in step 301 (No), the process proceeds to step S302, but when it is not determined whether or not the predetermined time T1 has elapsed, that is, when step S301 is omitted. The process may proceed to step S302. In this case, step S303 is also omitted.

  In step 303, the control circuit 1 sets a threshold value for determining whether or not the uniformity is lost to a second threshold value (the threshold value of method 2) smaller than the first threshold value. That is, even if high-accuracy cell balance processing is performed, if the predetermined time T1 has elapsed, it is estimated that the voltages of the batteries B1 to B4 are not equal or in an equal range, and the processing of step 303 is performed.

  In step 304, the control circuit 1 determines whether or not the voltage difference between the maximum voltage and the minimum voltage of the CCV measured under the condition of the method 1 or the condition of the method 2 is equal to or greater than a threshold value. If it is equal to or greater than the threshold (Yes), the process proceeds to step S8 in FIG. 2, and if it is not equal to or greater than the threshold (No), the process proceeds to step S305.

In step 305, the control circuit 1 waits for a predetermined time, and after waiting, shifts to step 1.
FIG. 4 is a flow diagram illustrating one embodiment of the operation of methods 3 and 4. In step 401, the control circuit 1 performs cell balance processing (high-accuracy cell balance processing) with the first cell balance amount of method 3 or method 4, and determines whether or not a predetermined time T2 has elapsed, When the predetermined time T2 has elapsed (Yes), the process proceeds to step S403.

  In step 402, the control circuit 1 sets a threshold value for determining whether or not the uniformity is lost to a third threshold value (threshold value of method 3). Note that if the predetermined time T2 has not elapsed in step 401 (No), the process proceeds to step S402. However, if it is not determined whether the predetermined time T2 has elapsed, that is, step S401 is omitted. In this case, the process may move to step S302. In this case, step S403 is also omitted.

  In step 403, the control circuit 1 sets a threshold value for determining whether or not the uniformity is lost to a fourth threshold value (the threshold value of method 4) smaller than the third threshold value. That is, even if high-accuracy cell balance processing is performed, if the predetermined time T2 has elapsed, it is estimated that the voltages of the batteries B1 to B4 are not equal or in an equal range, and the processing of step 403 is performed.

  In step 404, the control circuit 1 determines whether or not the voltage difference between the maximum voltage and the minimum voltage of the OCV estimated based on the CCV measured under the condition of the method 3 or the condition of the method 4 is equal to or greater than a threshold value. If it is equal to or greater than the threshold (Yes), the process proceeds to step S8 in FIG. 2, and if it is not equal to or greater than the threshold (No), the process proceeds to step S405.

In step 405, the control circuit 1 waits for a predetermined time, and after waiting, shifts to step 1.
As described above, by performing the cell balance processing using the second cell balance amount of the method 1 to the method 4, even when a highly accurate OCV cannot be obtained, the second cell balance less than the first cell balance amount. By executing the cell balance process using the amount, the voltage or capacity of the actual battery can be made as uniform as possible.

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

1 control circuit,
2a, 2b, 2c, 2d voltmeter,
B1, B2, B3, B4 batteries,
R1, R2, R3, R4 resistance,
SW1, SW2, SW3, SW4, SW5 switch,

Claims (6)

An assembled battery having a plurality of batteries;
A cell balance circuit for equalizing the voltage or capacity of each of the batteries;
A control circuit for controlling the cell balance circuit,
The control circuit includes:
When no current flows through the battery pack, or when a constant current flows through the battery pack, the cell balance process is executed using the first cell balance amount determined by the voltage difference between the batteries,
The second cell balance amount smaller than the first cell balance amount determined by the voltage difference between the batteries, even when no current flows through the assembled battery or when a constant current flows through the assembled battery. To execute the cell balance process,
A charging device characterized by that. The charging device according to claim 1,
The control circuit causes the cell balance processing to be executed using the first cell balance amount, and when a predetermined time has not elapsed and the voltage difference in the closed circuit voltage of each of the batteries is equal to or greater than a first threshold, Cell balance processing is executed using the second cell balance amount determined by the voltage difference.
A charging device characterized by that. The charging device according to claim 1,
When the voltage difference in the closed circuit voltage of each of the batteries is equal to or greater than a second threshold, the control circuit causes the cell balance process to be performed using the second cell balance amount determined by the voltage difference.
A charging device characterized by that. The charging device according to claim 1,
The control circuit executes a cell balance process using the first cell balance amount, and when a predetermined time has not elapsed, a voltage difference in an open circuit voltage estimated based on a closed circuit voltage of the battery is a first difference. If the threshold is greater than or equal to three thresholds, the cell balance process is executed using the second cell balance amount determined by the voltage difference.
A charging device characterized by that. The charging device according to claim 1,
When the voltage difference in the open circuit voltage estimated based on the closed circuit voltage of the battery is greater than or equal to a fourth threshold value, the control circuit uses the second cell balance amount determined by the voltage difference to perform cell balance processing To execute,
A charging device characterized by that. An assembled battery having a plurality of batteries;
A cell balance circuit for equalizing the voltage or capacity of each of the batteries;
A control circuit for controlling the cell balance circuit, and a control method for a charging device comprising:
The charging device is:
When no current flows through the assembled battery, or when a constant current flows through the assembled battery, a cell balance process is performed using a first cell balance amount determined by a voltage difference between the batteries,
The second cell balance amount smaller than the first cell balance amount determined by the voltage difference between the batteries, even when no current flows through the assembled battery or when a constant current flows through the assembled battery. Execute cell balance processing using
A control method for a charging device.

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