JP2007250364A - Internal charging device and charging method of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal charging technology which charges secondary batteries well in balance without making a device complicated. <P>SOLUTION: In a step S1, a voltage V1 and a voltage V2 of a battery 1 and a battery 2 are measured and a magnitude correlation between the two voltages are discriminated. As shown in a step S2, the voltage V1 of the battery 1 and the voltage V2 of the battery 2 are measured to be compared with each other. In the case of V1>V2 (YES), since it is estimated that a charged amperehour of the battery 2 is smaller than a charged amperehour of the battery 1, a user proceeds to a step S3, and the battery 2 having the smaller charged amperehour is charged. A process of the step S3 is repeated until a formula V1-V2<Δ is satisfied in a step S4, where Δ is a value near zero in a degree that V1 and V2 can be equated with each other. When the formula V1-V2<Δ is satisfied (YES) in the step S4, the user proceeds to a step S5, and the battery 1 and the battery 2 are connected in series to be charged. When the charging is finished, the process is completed (step S6). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal charging technique for a secondary battery, and more particularly, to an internal charging technique in a device that uses two or more commercially available secondary batteries such as nickel metal hydride batteries in series.

  Conventionally, internal charging has not been possible in devices using two or more commercially available (AA, AAA) secondary batteries such as nickel metal hydride batteries in series. FIG. 9 is a diagram illustrating a position configuration example of a charging set for charging two general secondary batteries. As shown in FIG. 9A, in order to connect the battery A and the battery B in series and charge them with the voltage V, for example, it is assumed that the batteries A and B have the same charge amount, for example, both are empty. Become. That is, in the charger shown in FIG. 9B, two charging circuits, a charging circuit (1) for battery A and a charging circuit (2) for battery B, are prepared, and both batteries are charged independently. There was a need to do. Alternatively, the batteries were once taken out and each battery was charged separately with a dedicated charger.

In the technique described in Patent Document 1 below, a plurality of secondary batteries are charged by switching from a serial charging state to a parallel charging state.
Japanese Patent Laid-Open No. 7-282853

  In the conventional technology, since a secondary battery of a commercial type is used unlike a dedicated battery, a combination of batteries having different charge amounts is generated, so that when the batteries are charged in series at the same time, the initial charge amount is different. There are many cases, and at the same time, the battery is not fully charged and one battery is always fully charged, and then the other battery is fully charged with a delay. Therefore, the battery that has been completely charged first becomes overcharged, and there is a problem that heat generation due to abnormal heat generation or deterioration of only one battery due to overcharge occurs.

  Further, the method described in Patent Document 1 has a problem that the device itself becomes complicated because it is necessary to charge a plurality of secondary batteries by switching from a serial charging state to a parallel charging state. It was.

  An object of this invention is to provide the internal charging technique which can charge a secondary battery with sufficient balance, without complicating an apparatus.

  According to one aspect of the present invention, a first step of measuring a voltage difference between each of the first secondary battery and the second secondary battery, and the voltage difference is greater than a certain allowable value In addition, a second step of charging the secondary battery having a smaller voltage, a step of repeating the first step and the second step until the voltage difference becomes smaller than the allowable value, and the voltage difference Charging the secondary battery, comprising: charging the first secondary battery and the second secondary battery in series when the battery becomes smaller than the allowable value. A method is provided.

  Further, a first step of measuring a voltage difference between the first secondary battery and the second secondary battery, and when the voltage difference is larger than a certain allowable value, A second step of discharging the secondary battery, a step of repeating the first step and the second step until the voltage difference becomes smaller than the allowable value, and the voltage difference being smaller than the allowable value. In this case, there is provided a method of charging a secondary battery, comprising: charging the first secondary battery and the second secondary battery by connecting them in series.

  The allowable value is preferably a value within a range where the charge amounts of the first secondary battery and the second secondary battery can be regarded as substantially the same.

  According to another aspect of the present invention, there is provided a charging device capable of charging a plurality of secondary batteries, wherein the plurality of secondary batteries are stored in a chargeable / dischargeable manner independently or in a series connection. A charger, a control unit that performs control to switch between a configuration that charges the charger independently and a configuration that charges in series connection, a voltage detection unit that detects a voltage of each of the secondary batteries, There is provided a charging device having a charging control circuit including a battery housing portion and a terminal portion for connecting the charger.

  When the voltage difference between each of the first secondary battery and the second secondary battery is larger than a certain allowable value, the control unit selects the secondary battery having a smaller voltage as the voltage. Charging is repeated until the difference becomes smaller than the allowable value, and when the voltage difference becomes smaller than the allowable value, the first secondary battery and the second secondary battery are connected in series. It is preferable to perform charging control.

  When the voltage difference between each of the first secondary battery and the second secondary battery is larger than a certain allowable value, the control unit determines that the secondary battery having a larger voltage is the voltage. When the discharge is repeated until the difference becomes smaller than the allowable value, and the voltage difference becomes smaller than the allowable value, the first secondary battery and the second secondary battery are connected in series. What controls charging may be used.

  According to the present invention, since it is not necessary to charge each secondary battery one by one, only one internal charging circuit is required, and the apparatus can be reduced in size and cost. Further, since charging is possible with the secondary battery mounted, there is an advantage that it is not necessary to prepare a dedicated charger.

Furthermore, when two batteries are charged separately at the same time, the charging current is divided into two. However, in the present invention, since the current is connected in series, the charging current can be halved. Become.
This is a case where the number of target batteries is two, and considering that the charging current flowing to each battery is the same as compared with the case where two batteries were initially charged at the same time, the charging current was reduced to 1/2. (The same charging current for each battery means the same charging completion time).

  The inventor has come up with the idea that the charge amount and voltage of the secondary battery are in a correspondence relationship, that is, the charge amount at that time is estimated by measuring the voltage of the secondary battery. In particular, for example, by measuring the voltage of each of the two secondary batteries, it is possible to know which secondary battery has a small amount of charge and therefore needs to be charged first from the magnitude relationship (high or low) of the voltage. In addition, by repeatedly measuring the voltage value of the secondary battery while charging each secondary battery until the same voltage is obtained, the same charge amount can be finally obtained. That is, when the amount of charge becomes substantially the same, the battery can be connected in series to perform internal charging of the battery.

  Hereinafter, based on the above viewpoint, an internal charging technique according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the basic principle of the internal charging technique according to this embodiment. FIG. 2 is a diagram illustrating a simplest sequence example of the charging process. Here, a description will be given by taking a charging process of two secondary batteries as an example.

  First, as shown in FIG. 1A, the battery (battery 1) on the left side of the figure is charged with voltage V1 (current I1) for, for example, Δt1 time (FIG. 2). On the other hand, as shown in FIG. 1B, the battery (battery 2) on the right side of the figure is charged with voltage V2 (current I2) for, for example, Δt2 time (FIG. 2). In FIG. 2, the sequence in which the battery 1 and the battery 2 are charged in series in terms of time is described as an example, but they may be charged in parallel. After such charging is repeated several times, for example, when it is determined that the charge amounts of both are almost the same, two batteries of the battery 1 and the battery 2 are connected in series, and charging is performed for, for example, Δt time. Thus, after continuing the process which charges two rechargeable batteries first until the time which is an independent state one by one, two rechargeable batteries are connected in series and charged. When charging in this way, the method according to the present embodiment requires a shorter time as long as the currents for charging are the same as compared with the case of charging two batteries individually. Considering the same charging time, the current required for charging can be reduced.

  This is because the charging time is determined by the charging current flowing to each battery. If the current is the same (to each battery), the charging time is equivalent. Since the amount of charge is the integrated amount of current (A) × time (h), the amount of charge (Ah), the charge time is proportional to the charge current. However, the application of the charging amount by this charging current is well applied to nickel-cadmium batteries and nickel-metal hydride batteries, but the charging method for lithium-ion batteries is partially different, so the above charging current x time integrated amount is charged. The calculation of quantity is not valid.

  FIG. 3 is a flowchart showing one processing example of the internal charging method of the secondary battery according to the present embodiment in which the above-described processing is summarized. The description will be made with reference to FIGS. 1 and 2 as appropriate. First, in step S1, the magnitudes of the voltage V1 and the voltage V2 of the battery 1 and the battery 2 are determined by measurement. Next, as shown in step S2, the voltage V1 of the battery 1 and the voltage V2 of the battery 2 are measured, and V1 and V2 are compared. When V1> V2 (YES), it can be estimated that the battery 2 has a smaller charge amount than the battery 1, and thus the process proceeds to step S3, and the battery 2 which is the battery having the smaller charge amount is charged. In step S4, the process of step S3 is repeated until V1−V2 <Δ, and V1−V2 <Δ (Δ is a value close to 0 and small enough to be considered that V1 and V2 are substantially the same. (YES), the process proceeds to step S5, the battery 1 and the battery 2 are connected in series to perform charging, and the process ends when the charging is completed (step S6).

  On the other hand, in step S2, when the voltage V1 of the battery 1 and the voltage V2 of the battery 2 are measured and V1 and V2 are compared, if V1 <V2 (NO), the battery 1 is more than the battery 2 Since it can be estimated that the amount of charge is small, the process proceeds to step S7, and the battery 1, which is the battery with the smaller amount of charge, is charged. In step S8, the process of step S7 is repeated until V2−V1 <Δ, and V1−V2 <Δ (Δ is a value close to 0 and small enough to be considered that V1 and V2 are substantially the same. (YES), the process proceeds to step S9, the battery 1 and the battery 2 are connected in series to perform charging, and when the charging is completed, the process is terminated (step S6). When the measurement result in step S2 is V1-V2 <Δ from the beginning, the process proceeds directly to step S5 or step S9.

  Thus, by performing internal connection in series connection for the first time at the time when the voltages of both battery 1 and battery 2, that is, the amount of charge becomes the same, both batteries are made to have an equal amount of charge in internal charging. be able to.

  Instead of performing adjustment by charging, it is also possible to perform the process of adjusting the charge amounts of the two batteries to be approximately the same by performing the process of discharging the battery with the larger charge amount.

  Next, a specific configuration example of a device having an internal charging function will be described. FIG. 4 is a functional block diagram showing a configuration example of the internal charging device for the secondary battery according to the present embodiment. As shown in FIG. 4, the internal charging circuit X according to the present embodiment charges the electronic device set (for example, a digital camera or a dedicated charging kit thereof) 11, the first battery 17, and the second battery 21. For example, a secondary battery housing 30 including a wiring L, a + terminal 31 and a − terminal 35 provided in the electronic device set 11 and connected to the wiring L, and a switch SW (ON / OFF controlled by the charge control circuit 15, for example) 1) 23, SW (2) 25, SW (3) 27, each of the first battery 17 and the second battery 21 being connected independently or in series for charging. SW that can be configured so that

  The voltage between the positive terminal 31 and the negative terminal 35 can be detected by, for example, a voltmeter 37. Electric power is supplied from the set 11 side to the battery side during charging and from the battery side to the set 11 side during discharging via the + terminal 31 and the − terminal 35. For example, the charge control circuit 15 includes a general charger 15a, a control unit 15b that controls the charging voltage of the charger, the opening / closing of the SW, and the like, and voltage detection means that can detect the respective voltages of the secondary battery. 15c.

  FIG. 5 is a diagram illustrating a state during discharge. As shown in FIG. 5, at the time of discharging, SW (1) 23 is on (conducting), SW (2) 25 is off (non-conducting), and SW (3) 27 is off (non-conducting). In this state, the first battery 17 and the second battery 21 are discharged.

  FIG. 6 is a diagram illustrating a state when the first battery 17 is charged. As shown in FIG. 6, when the first battery 17 is charged, SW (1) 23 is off, SW (2) 25 is off, and SW (3) 27 is on. Only one battery 17 is charged from the set 11.

  FIG. 7 is a diagram illustrating a state when the second battery 21 is charged. As shown in FIG. 7, when the second battery 21 is charged, SW (1) 23 is off, SW (2) 25 is on, and SW (3) 27 is off. Only the second battery 21 is charged from the set 11.

  FIG. 8 is a diagram showing a state in which both the first battery 17 and the second battery 21 are connected in series and are charged simultaneously. As shown in FIG. 8, when both batteries 17 and 21 are charged, SW (1) 23 is on, SW (2) 25 is off, and SW (3) 27 is off. Depending on the state of these SWs, Both the first battery 17 and the second battery 21 are charged from the set 11 to the series connection of the batteries 17 and 21.

  As described above, when the internal charging device according to the present embodiment is used, there is an advantage that the device can be simplified because two secondary batteries can be charged by one charging control circuit. In other words, since it is not necessary to charge the batteries one by one, it is possible to control with a single charging circuit, which makes it possible to reduce the size and cost of the device. Since charging can be performed with the battery attached, there is no need to provide a dedicated charger. Further, when two batteries are charged separately at the same time, the charging current is divided into two. However, since the current is serially charged, there is an advantage that the charging current is reduced to about half.

  In the present embodiment, the technique of charging by finally connecting two secondary batteries in series has been specifically described. However, even in the case of three or more batteries, charging can be performed on the same principle. .

  The present invention can be used for an internal charger or a device including the same.

It is a figure which shows the basic principle of the internal charging technique by one embodiment of this invention. It is a figure which shows the simplest sequence example of a charging process. It is a flowchart figure which shows the example of 1 process of the internal charging method of the secondary battery by this Embodiment. It is a functional block diagram which shows the example of 1 structure of the internal charging device of the secondary battery by this Embodiment. It is a figure which shows the mode of the circuit at the time of discharge. It is a figure which shows the mode at the time of charge of a 1st battery. It is a figure which shows the mode at the time of charge of a 2nd battery. It is a figure which shows a mode when charging both the battery of a 1st battery and a 2nd battery in series simultaneously. It is a figure which shows the example of 1 structure of the charge set which charges two general secondary batteries.

Explanation of symbols

L ... wiring, X ... internal charging circuit, 11 ... electronic device set, 15 ... charge control circuit, 17 ... first battery, 21 ... second battery, 23 ... switch SW (1), 25 ... SW (2) 27 ... SW (3) 31 ... + terminal, 35 ...- terminal.

Claims (7)

A first step of measuring a voltage difference between each of the first secondary battery and the second secondary battery;
A second step of charging a secondary battery having a smaller voltage when the voltage difference is larger than a certain allowable value;
Repeating the first step and the second step until the voltage difference is less than the allowable value;
A secondary battery comprising a step of charging the first secondary battery and the second secondary battery in series when the voltage difference is smaller than the allowable value; Charging method. A first step of measuring a voltage difference between each of the first secondary battery and the second secondary battery;
A second step of discharging the secondary battery having a larger voltage when the voltage difference is larger than a certain allowable value;
Repeating the first step and the second step until the voltage difference is less than the allowable value;
A secondary battery comprising a step of charging the first secondary battery and the second secondary battery in series when the voltage difference is smaller than the allowable value; Charging method.   3. The secondary according to claim 1, wherein the allowable value is a value within a range in which charge amounts of the first secondary battery and the second secondary battery can be regarded as substantially the same. 4. How to charge the battery. A charging device capable of charging a plurality of secondary batteries,
A battery housing portion for housing the plurality of secondary batteries independently or in series connection so as to be chargeable / dischargeable;
A charger,
A control unit that performs control to switch between a configuration in which charging by the charger is independently performed and a configuration in which charging is performed in series connection; a voltage detection unit that detects each voltage of the secondary battery; the battery housing unit; A charging device comprising: a terminal unit that connects the charger; and a charging control circuit that includes the charging unit.   When the voltage difference between each of the first secondary battery and the second secondary battery is larger than a certain allowable value, the control unit selects the secondary battery having a smaller voltage as the voltage. Charging is repeated until the difference becomes smaller than the allowable value, and when the voltage difference becomes smaller than the allowable value, the first secondary battery and the second secondary battery are connected in series. The charging device for a secondary battery according to claim 4, wherein charging is controlled.   When the voltage difference between each of the first secondary battery and the second secondary battery is larger than a certain allowable value, the control unit determines that the secondary battery having a larger voltage is the voltage. When the discharge is repeated until the difference becomes smaller than the allowable value, and the voltage difference becomes smaller than the allowable value, the first secondary battery and the second secondary battery are connected in series. The charging device for a secondary battery according to claim 4, wherein charging is controlled.   The electronic device which incorporates the charging device of any one of Claim 4-6.

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