JP6512823B2 - Charging device and control method - Google Patents

Description

  The present invention relates to, for example, a charging device for charging a battery pack such as a lithium ion secondary battery and a control method of the charging device.

  The charge voltage of the battery cell of the lithium ion secondary battery is often 4.2 V, and when two battery cells are connected in series, twice the voltage can be taken out and the charge voltage at the time of charging is also doubled Become 8.4V.

  However, when there is a difference between the capacities of the two battery cells, the cell balance collapses, and when charging at 8.4 V, the voltage of one battery cell is 4.0 V and the voltage of the other battery cell is 4.4 V. As such, a potential difference may occur between the two battery cells. Therefore, in order to ensure the safety of the battery cell, the battery pack is provided with a protection circuit that protects the overcharge by interrupting the charging current with a FET that controls the current, for example, when the voltage reaches 4.23 V per cell. It is done.

  As a general charging method for the battery pack, constant current constant voltage charging is performed, and when the charging current value below the full charge detection current value is detected during constant voltage charging, the charging circuit is determined to be full charge and charging is terminated. A technology is known (first prior art). Further, as a method of charging a battery pack having an overcharge protection circuit, Patent Document 1 proposes a technique of repeating pulse charge and discharge so as not to exceed the protection voltage (second prior art).

Unexamined-Japanese-Patent No. 8-289478

  However, in the prior art example 1, when the cell balance of the plurality of battery cells collapses and the protection circuit operates, the charging path is cut off and the charging current does not flow. Therefore, the charge current value becomes equal to or less than the full charge detection current value, and the charge circuit is determined to be fully charged, and the charge is ended. In this state, since the voltage of the battery cell is high due to the internal resistance of the battery cell, if the charging current value is lowered, the protection circuit does not operate and charging is completed without charging the chargeable capacity. I will.

  On the other hand, in the prior art example 2, when the pulse charge / discharge is repeated many times, when the charge is finished, the charge is carried out more than necessary and the battery cell becomes overcharged, which causes the battery cell to deteriorate. .

The present invention aims to a plurality of battery cells even when the protection circuit for protecting a plurality of battery cells from the overcharge is actuated to cut with charging.

The charging apparatus according to the present invention, there is provided a charging apparatus for charging a battery pack and a protection circuit for protecting a plurality of battery cells connected in series, the plurality of battery cells from the overcharge, for said battery pack current detecting means for detecting the charging current, during constant voltage charging period after the constant current charging period, charging current detected I by the current detecting means is a is less than a first value the first when it is smaller second value higher than the value, a first charging control process to terminate charging of the battery pack and determines that the fully charged in the constant voltage charging period, the If charge current detected I by the current detecting means is less than the second value, it is determined that the overcharge protection by the protection circuit is performed, overcharge protection is the protection circuit a second charging control process to wait until it is released, If overcharge protection serial protection circuit waits until terminated, the third performs the charging control process of performing the constant current charging of the battery pack at a lower charging current than the charging current in the constant current charging period And control means.
A control method according to the present invention is a control method of a charging device for charging a battery pack having a plurality of battery cells connected in series and a protection circuit for protecting the plurality of battery cells from overcharging, A current detection step of detecting a charging current for the battery pack, and a case where the charging current detected in the current detection step is less than a first value during a constant voltage charging period after the constant current charging period, A first charging control step of determining that the battery pack is fully charged and ending charging of the battery pack if the second value is smaller than a value of 1 and the current detection during the constant voltage charging period; If the charging current detected in the step is less than the second value, it is determined that the overcharge protection is performed by the protection circuit, and the process waits until the overcharge protection by the protection circuit is released. The second And a third charge control for performing constant current charging of the battery pack with a charging current lower than the charging current during the constant current charging period, when the control step and standby until the overcharge protection by the protection circuit is released. And step.
A program according to the present invention is a program for controlling a charging device for charging a battery pack having a plurality of battery cells connected in series and a protection circuit for protecting the plurality of battery cells from overcharging, A current detection step of detecting a charge current to the battery pack, and a case where the charge current detected in the current detection step is less than a first value during a constant voltage charge period after a constant current charge period, A first charge control step of determining that the battery pack is fully charged and ending charging of the battery pack if the second value is equal to or greater than the second value smaller than the first value; If the charge current detected in the current detection step is less than the second value, it is determined that the overcharge protection by the protection circuit is performed, and the overcharge protection by the protection circuit is canceled. In the second charge control step of waiting and when waiting until the overcharge protection by the protection circuit is canceled, constant current charging of the battery pack is performed with a charging current lower than the charging current during the constant current charging period. The computer is caused to execute a third charge control step to be performed.

According to the present invention, the plurality of battery cells can be charged even when the protection circuit for protecting the plurality of battery cells from overcharging is activated .

FIG. 2 is a block diagram for describing components included in the charging device 100 and the battery pack 200 in Embodiment 1. FIG. 6 is a flowchart for describing an example of a charge control method for the battery pack 200. FIG. (A), (b) and (c) are figures for demonstrating the example of the charge characteristic of the charging device 100. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram for explaining components of the charging apparatus 100 and the battery pack 200 according to the first embodiment.

  As shown in FIG. 1, the charging apparatus 100 includes an AC input unit 101, an AC / DC converter 102, a control unit 103, a current control element 104, a current detection element 105, and a display unit 106. Battery pack 200 is attached to charging device 100. Battery pack 200 is removable from charging device 100. At least one of the AC input unit 101, the AC / DC converter 102, the control unit 103, the current control element 104, the current detection element 105, and the display unit 106 has a hardware configuration.

  The AC input unit 101 is connected to a commercial power outlet via a cable with a plug or a direct plug, and supplies power to the charging apparatus 100. The AC / DC converter 102 rectifies the AC voltage and converts it to a DC voltage suitable for charging.

  The control unit 103 detects the temperature, charging voltage, and charging current of the thermistor 205 of the battery pack 200, and performs charge control on the battery pack 200. The current control element 104 is an element that controls the charging current using a transistor, a field effect transistor (FET), or the like, and is controlled by the control unit 103.

  The current detection element 105 is configured of a resistor or the like, and the control unit 103 detects a voltage difference between both ends of the resistor to detect the charging current. The display unit 106 is configured of an LED (Light Emitting Diode) or the like, and displays a charging state of the battery pack 200.

  The battery pack 200 includes a protection circuit 201, a plurality of battery cells 202 and 203, a field effect transistor (FET) 204, and a thermistor 205.

The protection circuit 201 detects the voltage and charge / discharge current of the plurality of battery cells 202 and 203, and when the detected value reaches, for example, a predetermined voltage value per cell, the FET 204 cuts off the charge current to perform overcharge protection.

  The plurality of battery cells 202 and 203 are chargeable and dischargeable secondary batteries such as lithium ion batteries. In FIG. 1, two battery cells 202 and 203 are connected in series to constitute battery pack 200, but three or more battery cells may be connected in series to constitute battery pack 200. .

  The FET 204 is a switch circuit for interrupting charge and discharge under the control of the protection circuit 201. The thermistor 205 detects the temperatures of the plurality of battery cells 202 and 203.

  FIG. 2 is a flowchart for explaining an example of a charge control method for the battery pack 200. The processing described with reference to FIG. 2 is controlled by the control unit 103 executing a program stored in a memory or the like of the charging apparatus 100.

  In FIG. 2, in step S101, when detecting the connection of the thermistor 205 of the battery pack 200, the control unit 103 determines that the battery pack 200 is attached to the charging device 100, and proceeds to step S102.

  In step S102, the control unit 103 determines the charging condition according to the temperature condition and the battery voltage condition based on the detection result of the temperature of the thermistor 205, starts charging the battery pack 200 under the determined charging condition, and proceeds to step S103. Go to

  In step S103, the control unit 103 measures the voltage across the current detection element 105 to detect the charging current, and the process proceeds to step S104. The current detection method here is generally a method of always detecting the charging current by sampling at a constant interval, and the sampling interval is set sufficiently finely with respect to the current change amount due to the normal charging characteristic.

  In step S104, the control unit 103 determines whether the current value of the charging current detected in step S103 is less than a first set value. If the current value of the charging current detected in step S103 is less than the first set value (YES in step S104), the control unit 103 proceeds to step S105. If the current value of the charging current detected in step S103 is greater than or equal to the first set value (NO in step S104), the control unit 103 returns to step S103.

  In step S105, the control unit 103 determines whether the current value of the charging current detected in step S103 is less than a second set value smaller than the first set value. If the current value of the charging current detected in step S103 is less than the second set value (YES in step S105), the control unit 103 performs overcharge protection by the protection circuit 201 of the battery pack 200 in step S106. It is determined that the process is performed and the process proceeds to step S108. If the current value of the charging current detected in step S103 is equal to or greater than the second set value (NO in step S105), the control unit 103 determines that the battery is fully charged in step S107 and ends the charging process.

  In step S108, the control unit 103 waits for a predetermined time until the overcharge protection by the protection circuit 201 of the battery pack 200 is released and the battery can be charged, and the process proceeds to step S109. As a method of canceling the overcharge protection by the protection circuit 201, a method of discharging for a short time may be used instead of waiting for a predetermined time.

  In step S109, the control unit 103 controls the current control element 104 to lower the charging current value from the charging condition determined in step S102 to charge the battery pack 200, and the process proceeds to step S110.

  In step S110, the control unit 103 measures the voltage across the current detection element 105 to detect the charging current, and the process proceeds to step S111.

  In step S111, the control unit 103 determines whether the current value of the charging current detected in step S110 is less than the first set value. If the current value of the charging current detected in step S110 is less than the first set value (YES in step S111), the control unit 103 ends the charging process. If the current value of the charging current detected in step S110 is equal to or greater than the first set value (NO in step S111), the control unit 103 returns to step S110 and charges the battery pack 200 with the charging current value reduced. Repeat several times.

  In FIG. 3A, general constant current constant voltage charging is performed on the battery pack 200, and when charging current falls below the full charge detection current value, charging is determined to be full charging and charging is terminated. It is a figure for demonstrating an example of the charge characteristic of an apparatus. FIG. 3B is a diagram for explaining an example of the charging characteristic of the charging apparatus in which the protection circuit of the battery pack 200 is activated during charging and the charging is finished. In FIG. 3C, when the protection circuit of the battery pack 200 is activated during charging, the control unit determines that the overcharge protection is activated, and the charging device according to the first embodiment performs charging by reducing the charging current. It is a figure for demonstrating an example of the charge characteristic of.

  As described above, in the first embodiment, it is determined whether the overcharge protection circuit 201 of the battery pack 200 is activated or whether the full charge has been performed normally, and charge control is performed according to the determination result. . As a result, power corresponding to the capacity can be efficiently charged to the plurality of battery cells 202 and 203.

  The present invention is not limited to the one exemplified in the first embodiment, and can be appropriately changed without departing from the scope of the present invention.

  For example, in the first embodiment, when the charging current value is less than the first set value in step S111 of FIG. 2, the charging process is ended, but the present invention is not limited to this. For example, when it is determined in step S111 in FIG. 2 that the charging current value is less than the second set value again and it is determined that the overcharge protection by the protection circuit 201 is performed, it is determined that the charge is full and the charge process is performed. It may be finished.

  The present invention is also realized by executing the following processing. That is, software (program) for realizing the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU or the like) of the system or apparatus reads the program. It is a process to execute. It can also be realized by executing software (program) acquired via a network or various storage media on a personal computer (CPU, processor).

100 charging device 103 control unit 104 current control element 105 current detection element 200 battery pack 201 protection circuit 202, 203 battery cell

Claims (6)

A charging apparatus for charging a battery pack having a plurality of battery cells connected in series, and a protective circuit for protecting the plurality of battery cells from the overcharge,
Current detecting means for detecting a charge current for said battery pack,
During constant-voltage charge period after the constant current charging period, the current charge current detected me by the detecting means is smaller second than the first value a is less than a first value if the value or more, the first charging control process to terminate charging of the battery pack and determines that the fully charged in the constant voltage charging period, charging detected I by the current detecting means If Denden flow is less than the second value, it is determined that the overcharge protection is performed by the protection circuit, the second charging control to wait until overcharge protection by the protection circuit Ru is released A third charge control process for performing constant current charging of the battery pack with a charging current lower than the charging current during the constant current charging period when processing and waiting until overcharge protection by the protection circuit is released charging instrumentation, characterized in that it comprises a control means for bets . Overcharge protection before Symbol protection circuit, the charging device according to claim 1, characterized in that overcharge protection by the protection circuit is released from being released after a predetermined time has elapsed. Overcharge protection before Symbol protection circuit, the charging device according to claim 1 in which the discharge of the battery pack is characterized in that it is released after being performed for a predetermined time. Said control means, said constant current when at lower than the charge current during the charging period the charge current the constant current charging of the battery pack is being performed, the current charge current detected by the detection means of the first The charging device according to any one of claims 1 to 3 , wherein a fourth charging control process for ending the charging of the battery pack is performed when the value is less than the value of . A plurality of battery cells connected in series, the plurality of battery cells A method for controlling a charging device for charging a battery pack and a protection circuit for protecting from overcharging,
A current detecting step of detecting the charging current for the battery pack,
During constant-voltage charge period after the constant current charging period, the current detection step with the detected charge current is the first in the case is less than the value of the first value smaller second value higher than the In a case where there is a first charge control step of determining that the battery pack is fully charged and ending the charging of the battery pack,
During said constant voltage charging period, if charge current detected by said current detecting step is less than the second value, it is determined that the overcharge protection is performed by the protection circuit, the protection a second charge control step of waiting until the overcharge protection circuit Ru is released,
And a third charge control step of performing constant current charging of the battery pack with a charging current lower than the charging current during the constant current charging period when waiting until overcharging protection by the protection circuit is released. Control method characterized by A plurality of battery cells connected in series, a program for controlling a charging device for charging a battery pack and a protection circuit for protecting the plurality of battery cells from the overcharge,
A current detecting step of detecting the charging current for the battery pack,
During constant-voltage charge period after the constant current charging period, the current detection step with the detected charge current is the first in the case is less than the value of the first value smaller second value higher than the In a case where there is a first charge control step of determining that the battery pack is fully charged and ending the charging of the battery pack,
During said constant voltage charging period, if charge current detected by said current detecting step is less than the second value, it is determined that the overcharge protection is performed by the protection circuit, the protection a second charge control step of waiting until the overcharge protection circuit Ru is released,
A third charge control step of performing constant current charging of the battery pack with a charging current lower than a charging current during the constant current charging period when waiting until overcharging protection by the protection circuit is released; A program to make it run.