JP4079428B2 - Battery pack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery pack composed of a plurality of series cell sets.
[0002]
[Prior art]
In a battery pack composed of a plurality of cell groups connected in series, if there is a minute cell voltage collapse when the cell group is implemented, the cell voltage collapse may increase due to repeated charge and discharge. As the number of series increases, the possibility of cell voltage collapse increases.
[0003]
When the voltage of each cell collapses, when fully charged, charging is stopped by the cell with the highest cell voltage (high charge amount), and the end of discharge is stopped by the cell with the lowest cell voltage (low charge amount). As a result, if the cell voltage collapse increases, the capacity of the entire cell set becomes smaller than the capacity inherent in each cell.
[0004]
Therefore, in order to return to the original capacity, a method has been proposed in which each cell voltage is made uniform by trickle charging, detecting each voltage, and performing balance discharge on cells higher than a predetermined balance voltage ( For example, see Patent Document 1).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-106220
[Problems to be solved by the invention]
However, in the conventionally proposed method, the cell voltage is detected only when the cell voltage falls below the end-of-discharge voltage, and when the charge / discharge cycle is repeated near the center of the capacity region. Almost never work. Therefore, it does not operate so much in actual use, and when it operates, it becomes after the voltage difference becomes large. Therefore, it takes time to adjust the cell voltage, resulting in a problem that the charging time becomes very long.
[0007]
[Means for Solving the Problems]
The present invention solves the above-described problems, and suppresses heat generation of a resistor and enables the cell voltage to be adjusted efficiently.
[0008]
Therefore, the present invention provides a battery pack composed of a plurality of series cell sets, a cell voltage adjustment switch including a cell voltage adjustment switch and a resistor connected in parallel to each cell, and the cell set and an output terminal. A battery on / off control switch connected in between, a precharge circuit connected in parallel to the battery on / off control switch and a resistor, and a maximum voltage by measuring the voltage of each cell during charging And a control circuit that turns on the cell voltage adjustment switch corresponding to a cell other than the cell having the lowest voltage when the voltage difference between the value and the minimum value exceeds a certain value .
[0009]
In addition, the voltage difference to turn on the cell voltage adjusting switch corresponding to the cell other than the lowest cell voltage when exceeding the predetermined value between the maximum value and the minimum value voltage measured by the in each cell during charging And a control circuit for turning off the cell voltage adjustment switches of all cells after waiting for a predetermined time while maintaining the state where the cell voltage adjustment switch is turned on. When charging is performed with the adjustment switch turned on, the battery on / off control switch is turned off and the precharge switch is turned on.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a battery pack according to the present invention, where 1 is a cell set, 2 is a cell voltage adjustment switch, 3 is a battery On / Off control switch, 4 is a precharge circuit, and 5 is a control circuit. Indicates.
[0011]
In FIG. 1, a cell set 1 is a plurality of series cell sets in which a plurality of cells are connected in series, and a cell voltage adjustment circuit including a cell voltage adjustment switch 2 and a resistor is connected in parallel to each cell. When the cell voltage adjustment switch 2 is turned on, a resistor is connected in parallel with the cell. The cell voltage is adjusted by the resistor connected in parallel with the cell bypassing the charging current.
[0012]
A battery On / Off control switch 3 is connected between the cell set 1 and the output (+), and a precharge circuit 4 including a precharge switch and a resistor is connected in parallel to the battery On / Off control switch 3. Is done. The battery On / Off control switch 3 turns on / off the main charge / discharge, and the precharge circuit 4 charges the battery with a small current when the cell voltage becomes too low or when charging starts. The precharge switch is turned on and precharge through the resistor is executed.
[0013]
The control circuit 5 detects charge, discharge, neglect (state of neither charging nor discharging), voltage, current, variation between cells, and the like, and the cell voltage adjustment switch 2, battery On / Off control switch 3, precharge Various controls are performed by turning on / off the precharge switch of the circuit 4. For example, when an excessive current flows, the battery On / Off control switch 3 is turned off to cut off the current, and when the cell voltage becomes too low or at the start of charging, the battery is charged with a small current. Is performed by controlling on / off of the precharge switch of the precharge circuit 4 and the battery On / Off control switch 3. Further, when the number of times of charging / discharging increases, the voltage of each cell starts to vary, and the difference between the maximum and minimum voltages exceeds a certain range, the on / off of the cell voltage adjustment switch 2 is controlled.
[0014]
As described above, in the present embodiment, charging / discharging of the battery pack is performed from the outputs (+) − (−), and charging / discharging is stopped before the battery pack is in a dangerous state by the control circuit 5 of the battery pack. Is done. In addition, a precharge circuit 4 for charging with a minute current is incorporated when the cell voltage becomes too low or at the start of charging. Further, when cell voltage collapse occurs in each cell in each series, a resistor is inserted so as to short-circuit the cell so that the voltage can be adjusted, and a cell voltage adjustment switch 2 for controlling it is inserted. Although not shown, a circuit for measuring the voltage of each cell and a circuit for measuring charge / discharge current are also incorporated in the battery pack.
[0015]
When the voltage of each cell connected in series collapses, the current flowing in the cells other than the cell with the lowest voltage during charging is turned on by turning on the cell voltage adjustment switch 2 connected in parallel to each cell. Bypass, charge only the cell with the lowest voltage. On the other hand, by using the precharge function at this time, the battery On / Off control switch 3 is turned off and the precharge switch of the precharge circuit 4 is turned on to limit the charging current to a small amount. As a result, the charging current is limited to a small amount, and the bypass current is also reduced, so that the resistance value of the cell voltage adjustment circuit connected in parallel to the cell can be increased, the resistance heat generation is suppressed, and the cell voltage is reduced. Can be adjusted efficiently.
[0016]
Incidentally, in order to bypass most of the current of the rated charge, it is necessary to reduce the resistance connected in parallel with the cell. For example, if the cell voltage is 3.6 V and the charging current is 2 A, all current flows through the resistor. The resistance is 1.8Ω, the amount of power is 7.2W, and a resistance with a rating of about 10W is actually used, and it is difficult to ensure safety (heat generation, etc.), which is not practical. Although the effect of correcting the cell voltage collapse is reduced, the resistance value is increased if selection is made because of safety and relatively inexpensive parts. When the precharge function is used, the charging current is limited to be small, and the correction time for cell voltage collapse due to the extension of the charging time is lengthened. However, even if the bypass current is small, the effect of correcting the cell voltage collapse is improved.
[0017]
FIG. 2 is a diagram for explaining a control flow by the control circuit. First, each cell voltage is measured (step S1), and whether or not the difference between the minimum voltage and the maximum voltage of the cell is, for example, 30 mV or more. Is determined (step S2).
[0018]
In the case of YES (when the difference between the minimum voltage and the maximum voltage of the cell is 30 mV or more), the precharge switch of the precharge circuit 4 is turned on and the battery On / Off control switch 3 is turned off to limit the charging current. Prepare for balance circuit operation. At the same time, the cell voltage adjustment switch 2 other than the cell with the lowest voltage is turned on to bypass the charging current flowing through the cells other than the cell with the lowest voltage, and the charging current between the cell with the lowest voltage and the other cells is differentiated. Charging is performed in a direction to reduce the voltage difference (step S3).
[0019]
After waiting for a certain time while maintaining the control state of step S3 (step S4), the cell voltage adjustment switch 2 of all cells is turned off to return the currents of cells other than the bypassed minimum voltage cells to normal. Then, the normal state is restored (step S5), the process returns to step S1 and the same control is repeatedly executed.
[0020]
On the other hand, when the determination process of step S2 is NO (when the difference between the minimum voltage and the maximum voltage of the cell is not 30 mV or more), the precharge switch of the precharge circuit 4 is turned off and the battery On / Off control switch 3 is turned on. Then, the cell voltage adjustment switches 2 of all cells are turned off (step S6). That is, since there is no voltage difference, both the precharge switch 4 of the precharge circuit 4 and the cell voltage adjustment switch 2 are turned off to return to the normal state, and the same control is repeatedly executed by returning to step S1.
[0021]
In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above-described embodiment, the cell voltage adjustment switch 2 is turned on, and the current flowing outside the cell having the lowest voltage is bypassed by the resistor during charging, and only the cell having the lowest voltage is charged. Thus, only the cell having the highest voltage may be controlled to perform charging after the cell voltage adjustment switch 2 is turned on for a certain period of time.
[0022]
【The invention's effect】
As is clear from the above description, according to the present invention, when the voltage of each cell connected in series collapses, the current that flows except for the cell with the lowest voltage during charging is bypassed to the resistor connected in parallel to each cell. By charging only the cell with the lowest voltage, the cell voltage collapse can be corrected and the original capacity can be recovered.
[0023]
At that time, in order to bypass most of the rated charge current, it is necessary to reduce the resistance connected in parallel with the cell, which is not practical, but the precharge function is used to reduce the charge current. By limiting it to a small value, the resistance value of the cell voltage adjusting circuit connected in parallel to the cell can be increased, the heat generation of the resistor can be suppressed, and the cell voltage can be adjusted efficiently.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a battery pack according to the present invention.
FIG. 2 is a diagram for explaining a control flow by a control circuit;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cell group, 2 ... Cell voltage adjustment switch, 3 ... Battery On / Off control switch, 4 ... Precharge circuit, 5 ... Control circuit

Claims (3)

In a battery pack composed of a plurality of series cell sets, a cell voltage adjustment circuit including a cell voltage adjustment switch and a resistor connected in parallel to each cell, and a battery connected between the cell set and an output terminal An on / off control switch, a precharge switch connected in parallel to the battery on / off control switch, and a resistor; and a maximum value and a minimum value obtained by measuring the voltage of each cell during charging. And a control circuit for turning on the cell voltage adjustment switch corresponding to a cell other than the cell having the lowest voltage when the voltage difference exceeds a certain value . In a battery pack composed of a plurality of series cell sets, a cell voltage adjustment circuit including a cell voltage adjustment switch and a resistor connected in parallel to each cell, and a battery connected between the cell set and an output terminal An on / off control switch, a precharge switch connected in parallel to the battery on / off control switch, and a resistor; and a maximum value and a minimum value obtained by measuring the voltage of each cell during charging. After the voltage difference exceeds a certain value, the cell voltage adjustment switch corresponding to a cell other than the cell having the lowest voltage is turned on, and after waiting for a certain time while keeping the cell voltage adjustment switch on. A battery pack comprising a control circuit for turning off cell voltage adjustment switches of all cells .   3. The control circuit according to claim 1, wherein when the battery is charged by turning on a cell voltage adjustment switch, the control circuit turns off the battery on / off control switch and turns on the precharge switch. 4. Battery pack.

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