JP2003199260A - Method and apparatus for charging secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To charge a secondary battery in a short time without enlarging a pulse current for pulse-charging. <P>SOLUTION: Charging currents of pulses which are out of timing from each other are supplied from a power supply 2 for charging to a plurality of secondary batteries 1, and the batteries are subjected to pulse chargings. When charging currents are not supplied from the power supply 2 for charging to the secondary batteries 1, or when charging currents smaller than preset currents are supplied from the power supply 2 for charging to the secondary batteries 1, the charging currents are supplied from the power supply 2 for charging to a standby battery 6, and the standby battery 6 is thereby charged. Further, the secondary batteries 1 are charged both with a standby charging current supplied from the charged standby battery 6 and with pulse charging currents supplied from the power supply 2 for charging with time shifted. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging method and a charging device for performing pulse charging to fully charge a plurality of secondary batteries.

[0002]

2. Description of the Related Art A method of pulse charging a plurality of secondary batteries has been developed (Japanese Patent Laid-Open No. 11-285161). In the charging method described in this publication, the pulses for charging the secondary battery are sequentially switched, and one secondary battery is charged with one pulse to be fully charged. The rechargeable battery that is pulse-charged is repeatedly charged and stopped in a short cycle. When charging any one of the secondary batteries, all other secondary batteries stop charging.

For example, when charging four secondary batteries, as shown in FIG. 1, a charging current is sequentially supplied to each secondary battery in a pulsed manner. In this figure, the secondary battery is charged with a charging current of 1.8 A for 0.5 seconds, and charging is suspended for 1.5 seconds. According to this charging method, the secondary current can be fully charged in a short time by increasing the pulse current for pulse charging. This is because the average charging current can be reduced to 0.45A by setting the pulse current to 1.8A.

According to the charging method shown in this figure, all the secondary batteries can be rapidly charged at an average current of 0.45 A and can be fully charged together. Therefore, all the secondary batteries can be fully charged in a short time. In the method of fully charging four secondary batteries with a continuous current of 0.45 A and switching the secondary batteries to be charged after full charging, four full batteries are four times as full charged. It takes time. In the method of performing pulse charging in order, while one of the secondary batteries is being pulse-charged, the charging of the other secondary batteries is suspended, so the charging current of one pulse is increased and the secondary battery is charged. Can be quickly charged in a short time. Moreover, since the pulses for pulse charging are switched in order and the charging of all the secondary batteries proceeds together, the overall charging time can be shortened.

[0005]

However, in order to further shorten the charging time in the pulse charging method, it is necessary to increase the pulse current during pulse charging. In order to increase the pulse current, it is necessary to increase the power source for charging, which increases the manufacturing cost. Further, when the pulse current for pulse charging the secondary battery increases, the performance of the secondary battery may deteriorate. Therefore, considering the deterioration of the battery performance during charging, it is preferable to make the pulse current for pulse charging as small as possible. However, if the peak current of pulse charging is reduced, the charging time will be longer and the user will not be able to use it conveniently.

That is, in pulse charging, it is necessary to increase the pulse current in order to shorten the charging time.
Not only does the cost of manufacturing the charging power source increase, but the charging environment is never favorable for battery performance. If the pulse current is reduced in consideration of battery performance, the charging time becomes long and it cannot be used conveniently.

The present invention was developed for the purpose of solving this drawback. An important object of the present invention is to provide a charging method and a charging device capable of charging a secondary battery in a short time without increasing the pulse current of pulse charging. Another important object of the present invention is to shorten the charging time without increasing the pulse current of pulse charging,
An object of the present invention is to provide a charging method and a charging device that can perform rapid charging with a low-cost charging power source without increasing the output current of the charging power source. Still another important object of the present invention is to provide a charging method and a charging device that can perform rapid charging while minimizing the deterioration of battery performance without increasing the pulse current.

[0008]

A method of charging a secondary battery according to the present invention is a method of charging a plurality of secondary batteries 1, wherein a plurality of secondary batteries 1 are charged at different timings from a charging power source 2. The charging currents of the shifted pulses are supplied to perform pulse charging.
In addition, this charging method uses the charging power source 2 to the secondary battery 1
When the charging current is not supplied to the secondary battery 1, or when the charging current from the charging power source 2 is supplied to the secondary battery 1 that is smaller than the set current, the charging current is supplied from the charging power source 2 to the spare battery 6 To charge. Further, the secondary battery 1 is charged by shifting the time by both the preliminary charging current supplied from the charged secondary battery 6 to the secondary battery 1 and the pulse charging current supplied from the charging power source 2 to the secondary battery 1. .

In the spare battery 6, the charging power source 2 is the secondary battery 1
Before the pulse charging of 1 is started, it can be charged by the charging power supply 2. Further, the spare battery 6 can be charged during the pulse charging. The secondary battery 1 can charge the secondary battery 1 via the voltage drop element 8. A diode can be used for the voltage drop element 8.

Further, according to the charging method of the present invention, even after any one of the secondary batteries 1 is fully charged, the secondary battery 1 which is not fully charged in the same cycle is pulse-charged to be fully charged. The spare battery 6 can be charged at the timing when the charging is stopped.

According to a seventh aspect of the present invention, there is provided a charging device for a secondary battery, which is connected between a charging power source 2 for charging a plurality of secondary batteries 1 and between the charging power source 2 and the secondary battery 1. A main charging switch 4 for switching the secondary battery 1 to be charged and a power source 2 for charging so that they are pulse-charged at different timings.
Is connected via the pre-charging switch 5 to the charging power source 2
A spare battery 6 to be charged with, a sub charging switch 7 connected between the spare battery 6 and the secondary battery 1, a sub charging switch 7, a main charging switch 4 and a preliminary charging switch 5
And a control circuit 3 for controlling ON and OFF. The control circuit 3 turns on / off the main charging switch 4 so as to pulse-charge the plurality of secondary batteries 1 in order, and turns on the preliminary charging switch 5 at a timing when the charging power supply 2 does not charge the secondary battery 1. Then, the charging power source 2 is controlled to charge the spare battery 6. Further, the control circuit 3 switches the main charging switch 4 on and off in order, and at the pulse charging timing for pulse charging the secondary battery 1, the main charging switch 4 is switched off and the charging power source 2 is not pulse charged. The sub-charging switch 7 connected to the secondary battery 1 is turned on, and the secondary battery 1 is charged by both the charging power source 2 and the spare battery 6.

The charging device of the present invention includes a sub charging switch 7
A diode can be connected between the battery and the secondary battery 1. The control circuit 3 can detect that the secondary battery 1 is not mounted and turn on the preliminary charging switch 5 to charge the preliminary battery 6 with the charging power source 2.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below exemplify a charging method and a charging device for embodying the technical idea of the present invention, and the present invention does not specify the charging method and the charging device as follows.

Further, in this specification, in order to facilitate understanding of the claims, the numbers corresponding to the members shown in the embodiments are referred to as "claims column" and "to solve the problem." It is added to the members shown in "Means column".
However, the members shown in the claims are not limited to the members of the embodiment.

FIG. 2 shows a circuit diagram of a charging device used in the charging method of the present invention. The charging device of this circuit diagram is connected between a charging power supply 2 for pulse-charging a plurality of secondary batteries 1 at different timings, and between the charging power supply 2 and the secondary battery 1 to be charged. The main charging switch 4 for switching the secondary battery 1 to be charged, the spare battery 6 connected to the charging power source 2 via the preliminary charging switch 5 and charged by the charging power source 2, the secondary battery 6 and the secondary battery A sub-charging switch 7 connected to the battery 1 and a control circuit 3 for controlling the sub-charging switch 7, the main charging switch 4, and the preliminary charging switch 5 to be turned on / off.

The charging power source 2 is controlled by the control circuit 3 to charge the secondary battery 1 with a constant current pulse at a predetermined current.
The charging power supply 2 is a switching power supply, and is a rectifier circuit 11 that rectifies an alternating current of 100 V and a switching circuit 12 that switches the direct current output from the rectifier circuit 11.
And a transformer 13 for inputting the alternating current switched by the switching circuit 12 to the primary side to drop the input voltage to the charging voltage of the secondary battery 1, and a direct current by rectifying the alternating current output from the transformer 13. And a CV / CC control circuit 15 for controlling the duty of switching of the switching circuit 12 by the output voltage of the rectifier circuit 14 and the signal from the control circuit 3.
And an insulating PC circuit 16.

The main charging switch 4 is switched on and off by the control circuit 3 at a constant cycle, and the secondary battery 1 is pulse-charged in sequence. In the pulse charging, the charging time is 0.5 seconds and the charging suspension time is 1.5 seconds, and the plurality of secondary batteries 1 are pulse-charged in order. However, the charging method of the present invention does not specify the charging time for pulse charging. The charging time of one pulse for pulse charging is set to, for example, 50 milliseconds to 10 seconds, preferably 0.1 to 5 seconds, more preferably 0.2 to 3 seconds, and most preferably 0.2 to 1 second. It

The charging time for one pulse is set to a time at which rapid charging can be performed without degrading battery performance. Further, when pulse-charging a plurality of secondary batteries 1, there are a method of pulse-charging all the secondary batteries 1 with the same charging current and a method of pulse-charging each secondary battery 1 with a different charging current.

The charging method for changing the charging current by the secondary battery 1 is such that the time width of one pulse is sufficiently longer than the time required to change the charging current, for example, for changing the charging current. The time is set to 3 times, preferably 10 times longer. To change the charging current by the secondary battery 1, as shown in the figure, the control circuit 3 controls the CV / CC control circuit 15 of the charging power source 2. In this charging method, the charging current of each pulse is controlled to charge the secondary battery 1 with the optimum charging current.

When changing the charging current of each pulse, it takes time to change the charging current. In the charging power supply 2 which is a switching power supply, the switching frequency for switching the switching circuit 12 on and off affects the time for changing the charging current. When the switching frequency is high, the time for changing the charging current of each pulse is short, and when the switching frequency is low, the time for changing the charging current of each pulse is long. Therefore, the cycle of switching the switching circuit 12 on and off is sufficiently shorter than one cycle of pulse charging, for example,
It is set to 1/100 or less.

The rest time in pulse charging is determined by the number of batteries charged together. This is because the pulses for charging all the batteries are switched in order to perform pulse charging. The rest time is (n−1) × T, where n is the number of batteries to be charged together and T is the charging time.

The main charging switch 4 is a transistor or FE.
Composed of T. Transistor main charge switch 4
Is connected to the output side of the charging power supply 2 by connecting the collectors to each other. The emitter of each transistor constituting the main charging switch 4 is connected to the positive side of the secondary battery 1, and the base is connected to the control circuit 3.

As shown in FIG. 3, the main charging switches 4 are controlled so that one of them is turned on and the other is turned off.
A plurality of secondary batteries 1 are sequentially and repeatedly pulse-charged. The main charging switch 4 is sequentially turned on to pulse-charge the secondary battery 1 in order. The main charging switch 4 connected to the fully charged secondary battery 1 is controlled to be turned off even when it is turned on. The main charging switch 4, which is connected to the secondary battery 1 that is not fully charged, is switched on at a constant cycle even after that.
Fully charge.

The main charging switch 4 is turned on / off by an output signal from the control circuit 3. The main charging switch 4, which is a transistor, is turned on when a base current flows from the control circuit 3 and turned off when the base current is cut off. The main charge switch 4 of the FET is controlled to be turned on when a voltage is applied to the gate and turned off when a gate voltage is not applied.

The control circuit 3 switches the plurality of main charging switches 4 on and off to pulse-charge the secondary battery 1.
Further, the charging circuit which does not charge all the secondary batteries 1 with the same charging current controls the CV / CC control circuit 15 of the charging power source 2 by the control circuit 3 to independently charge the charging current of each secondary battery 1. Control.

Further, the secondary battery 1 is charged not only by the charging power source 2 but also by the spare battery 6. Spare battery 6
Is connected to the charging power source 2 via the preliminary charging switch 5 and is charged by the charging power source 2. This spare battery 6 is
It is a battery of the same type as the secondary battery 1, and has a voltage substantially equal to that of the secondary battery 1 when fully charged. Further, the spare battery 6 is connected to the secondary battery 1 via the sub charging switch 7. When the preliminary charging switch 5 is turned on, the preliminary battery 6 is charged by the charging power source 2. When the sub charging switch 7 is turned on, the spare battery 6 charges the secondary battery 1. The preliminary charging switch 5 is controlled to be turned on and off by the control circuit 3 to charge the preliminary battery 6. Sub charging switch 7
Also, the secondary battery 1 is charged by being turned on / off by the control circuit 3. The pre-charge switch 5 and the sub-charge switch 7 are transistors and FETs, and are controlled by the control circuit 3 in the same manner as the main charge switch 4. The control circuit 3 does not turn on both the preliminary charging switch 5 and the sub charging switch 7. When both the pre-charging switch 5 and the sub-charging switch 7 are turned on, the charging power source 2
Is to charge both the spare battery 6 and the secondary battery 1. However, as shown in FIG. 2, in the circuit in which the voltage drop element 8 such as a diode is connected between the secondary battery 1 and the secondary battery 1, when the secondary battery 1 is charged, the preliminary charging switch is used. It is also possible to turn on both 5 and the sub charging switch 7. This is because the diode lowers the output voltage of the backup battery 6 and limits the backup charging current of the secondary battery 1. Furthermore, this diode blocks the flow of current from the secondary battery 1 to the spare battery 6.

In the control circuit 3, the charging power source 2 is the secondary battery 1
When not charging, the preliminary charging switch 5 is turned on to charge the auxiliary battery 6 with the charging power source 2. When the backup battery 6 is fully charged, the control circuit 3 turns off the backup charging switch 5 to prevent the backup battery 6 from being overcharged. The charging power source 2 does not charge the secondary battery 1 at the following timings, for example. When the charging power supply 2 is connected to the AC 100V power supply line but the secondary battery 1 is not installed. At this time, since the charging power source 2 cannot charge the secondary battery 1, the control circuit 3 turns on the preliminary charging switch 5 to charge the preliminary battery 6. The control circuit 3 detects that the secondary battery 1 is not attached, or detects that all the main charging switches 4 are turned off, and turns on the preliminary charging switch 5 to charge the preliminary battery 6. When all secondary batteries 1 are fully charged and charging is complete. Also at this time, the control circuit 3 detects that all the main charging switches 4 have been turned off, and the preliminary charging switch 5
Is turned on to charge the spare battery 6. Timing when one of the secondary batteries 1 is fully charged and the fully charged secondary battery 1 is charged. Multiple secondary batteries 1
When the battery is charged, one of the secondary batteries 1 is charged quickly. In this state, the control circuit 3 does not turn on the main charging switch 4 but turns on the preliminary charging switch 5 to fully charge the secondary battery 1 at the timing of charging the fully charged secondary battery 1. The spare battery 6 is charged instead of the secondary battery 1.

The spare battery 6 can be charged by the charging power supply 2 when the charging power supply 2 supplies a pulse charging current smaller than the set current to the secondary battery 1. This timing occurs when: When a plurality of rechargeable batteries 1 are pulse-charged at a constant cycle, if a small-capacity rechargeable battery 1 is installed, or the rechargeable batteries 1 are close to full charge and the time width for pulse charging is narrowed, When a rest time occurs when the secondary battery 1 is not charged. At this time, the control circuit 3 turns off all the main charging switches 4 at the timing when the preliminary charging switches 5 are turned on.
Is turned on to charge the spare battery 6. When the battery is close to full charge and the charging current value for pulse charging becomes smaller than the set value. When any one of the secondary batteries 1 approaches full charge and the battery voltage rises, and the pulse current supplied from the charging power source 2 having the constant voltage / constant current characteristic to the secondary battery 1 becomes less than the rated current. . For example, when the charging power supply 2 charges the AA type secondary battery 1 having a constant voltage characteristic with a pulse current of 1.8 A, the battery voltage increases and the pulse charging current of the secondary battery 1 decreases to 1 A. At this time, the charging power source 2 has a margin of 0.8 A at the timing of charging the battery. Therefore, the spare battery 6 can be charged with this current. At this time, the control circuit 3 turns on both the main charging switch 4 and the preliminary charging switch 5 to charge the preliminary battery 6.

The sub charging switch 7 charges the secondary battery 1 at the timing when the pulse charging is stopped. Therefore, the control circuit 3 turns on the sub-charging switch 7 connected to the secondary battery 1 at the timing when the main charging switch 4 connected to the secondary battery 1 is turned off.
Secondary battery 1 whose connected main charging switch 4 is turned on
The sub charging switch 7 connected to is switched off. Therefore, as shown in FIG. 3, the secondary battery 1 is supplied with the pulse charging current from the charging power source 2 at a predetermined cycle, and is supplied with the preliminary charging current from the spare battery 6 at the timing when the pulse charging current is not supplied. Will be charged. When the secondary battery 1 is fully charged, the control circuit 3 holds both the main charging switch 4 and the sub charging switch 7 in the off state, and ends the charging of the fully charged secondary battery 1.

The control circuit 3 has a microcomputer and an A / D converter for detecting a battery voltage and converting an analog voltage into a digital voltage. The on-voltage when each secondary battery 1 is being charged is input to the microcomputer from the A / D converter. The microcomputer calculates the input ON voltage and controls the main charging switch 4, the preliminary charging switch 5, the sub charging switch 7, and the charging power source 2. Further, the control circuit 3 also has a timer built therein, and controls the main charging switch 4 and the sub charging switch 7 with the timer and the battery voltage.

The control circuit 3 detects the on-voltage of the secondary battery 1 being charged, detects ΔV at which the on-voltage of each secondary battery 1 drops from the peak value, and detects full charge. The control circuit 3 can detect not only the on-voltage but also the off-voltage, which is the battery voltage when the charging is stopped, to detect the full charge. In this charging method, it is determined that the battery is fully charged by detecting that either the on-voltage or the off-voltage becomes the peak voltage or decreases by ΔV.

The control circuit 3 charges the secondary battery 1 according to the flowchart of FIG. In this flowchart, the spare battery 6 is charged after all the secondary batteries 1 are fully charged.
However, the present invention does not specify charging of the spare battery 6 at this timing.

[N = 1 step] The control circuit 3 turns on the main charging switch 4. In this state, the first secondary battery 1 is pulse-charged by being supplied with the pulse charging current from the charging power source 2. At this time, all other main charging switches 4, pre-charging switches 5 and sub-charging switches 7
Is held off. [Step of N = 2] In this step, the control circuit 3
A counter (not shown) is set to m = 1 in order to sequentially switch the n secondary batteries 1 and perform pulse charging. [Steps of N = 2, 3, 4, 5, 6, 7, 8] N = 2, 3, 4, 5, 6, 7 until the secondary battery 1 is fully charged.
The above steps are looped to pulse-charge the secondary battery 1. At this time, the secondary battery 1 is charged by the spare battery 6 during the pulse charging pause time. That is, the secondary battery 1 sets the timing at which the pulse charging current is supplied from the charging power source 2 and the timing at which the preliminary charging current is supplied from the spare battery 6 without supplying the pulse charging current from the charging power source 2 to be constant. Is repeatedly charged in the cycle. At this time, the control circuit 3 sequentially turns on the main charging switch 4 to pulse-charge the secondary battery 1. Further, the sub charging switch 7 connected to the secondary battery 1 to be pulse-charged is turned off,
The sub-charge switch 7 connected to the secondary battery 1 that is not pulse-charged is turned on, and the secondary battery 1 that is not pulse-charged is charged by the spare battery 6. Pre-charge switch 5
Is held off. When the full charge of the secondary battery 1 is detected, all the main charging switches 4 and all the sub charging switches 7 are kept off and the charging is completed. [Step N = 9] After that, the control circuit 3 turns on the preliminary charging switch 5 to charge the preliminary battery 6, and when the preliminary battery 6 is fully charged, turns off the preliminary charging switch 5.

The above flow chart shows a state in which a plurality of secondary batteries 1 are fully charged with substantially equal charge capacities, that is, a plurality of secondary batteries 1 are fully charged almost simultaneously. However, if multiple secondary batteries are fully charged with different charge capacities, that is, if there is a difference in the time until all secondary batteries are fully charged, although not shown, the fully charged secondary batteries The charging can be canceled to prevent the secondary battery from being overcharged.

[0035]

The secondary battery charging method and charging device of the present invention are characterized in that the secondary battery can be charged in a short time without increasing the pulse current for pulse charging. That is, when the charging method and the charging device of the present invention do not supply the charging current from the charging power source to the secondary battery, or when the charging power source supplies a charging current smaller than the set current to the secondary battery, charging is performed. The spare battery is being charged by supplying the charging current to the spare battery from the power supply for charging, and the standby charging current supplied from the charged spare battery and the pulse charging current supplied from the charging power source are both staggered in time. This is because the secondary battery is being charged. The charging method and the charging device of the present invention are different in that the pulse charging and the charging from the spare battery are staggered in time.
Since the secondary battery is charged at the timing when pulse charging is not performed, the secondary battery can be efficiently charged in a short time without increasing the pulse current of pulse charging. Thus, the charging method and the charging device of the present invention, which can charge the secondary battery in a short time without increasing the pulse current of the pulse charging, are for low-cost charging without increasing the output current of the charging power source. It can be charged rapidly with the power supply and can be charged rapidly while minimizing the deterioration of battery performance.

[Brief description of drawings]

FIG. 1 is a graph showing a timing of pulse charging a plurality of secondary batteries by a conventional charging method.

FIG. 2 is a circuit diagram of a charging device used in a charging method according to an embodiment of the present invention.

FIG. 3 is a graph showing the timing of pulse charging a plurality of secondary batteries by the charging method according to the embodiment of the present invention.

FIG. 4 is a flowchart showing a process of charging a plurality of secondary batteries with the charging device shown in FIG.

[Explanation of symbols]

1 ... Secondary battery 2 ... Power supply for charging 3 ... Control circuit 4 ... Main charging switch 5 ... Pre-charge switch 6 ... Spare battery 7 ... Sub charge switch 8 ... Voltage drop element 11 ... Rectifier circuit 12 ... Switching circuit 13 ... Transformer 14 ... Rectifier circuit 15 ... CV / CC control circuit 16 ... Insulation PC circuit

Claims (9)

[Claims] 1. A method of charging a plurality of secondary batteries (1), comprising supplying charging currents of pulses with mutually deviated timing from a charging power source (2) to the plurality of secondary batteries (1). Pulse charging, and when charging current is not supplied from the charging power supply (2) to the secondary battery (1), or when the charging power supply (2) is recharged from the secondary battery (1).
When a charging current smaller than the set current is supplied to, the charging power source (2) supplies the charging current to the spare battery (6) to charge the spare battery (6), and the charged spare battery (6) From secondary battery
Of the secondary battery that charges the secondary battery (1) at different times with both the preliminary charging current supplied to (1) and the pulse charging current supplied from the charging power supply (2) to the secondary battery (1). How to charge. 2. The charging power source (2) according to claim 1, wherein the charging power source (2) charges the spare battery (6) before the charging power source (2) starts pulse charging of the secondary battery (1). How to charge the next battery. 3. The method of charging a secondary battery according to claim 1, wherein the auxiliary battery (6) is charged during pulse charging. 4. The charging method for a secondary battery according to claim 1, wherein the secondary battery (6) charges the secondary battery (1) through the voltage drop element (8). 5. The method for charging a secondary battery according to claim 4, wherein a diode is used as the voltage drop element (8). 6. A fully charged secondary battery (1) is charged by pulse charging a secondary battery (1) that is not fully charged in the same cycle even after one of the secondary batteries (1) is fully charged. The method for charging a secondary battery according to claim 1, wherein the backup battery (6) is charged at a timing when charging is stopped. 7. A charging power source (2) for charging a plurality of secondary batteries (1), and a charging power source (2) and a secondary battery (1), which are connected to each other at different timings. Main charging switch that switches the secondary battery (1) to be charged, like pulse charging
(4), a backup battery (6) that is connected to the charging power supply (2) via the preliminary charging switch (5) and is charged by the charging power supply (2),
The sub-charging switch (7) connected between the spare battery (6) and the secondary battery (1), the sub-charging switch (7), the main charging switch (4) and the pre-charging switch (5). And a control circuit (3) for controlling the on / off of the main charging switch (4) so that the control circuit (3) pulse-charges the plurality of secondary batteries (1) in sequence. At the timing when the power supply (2) does not charge the secondary battery (1), turn on the preliminary charging switch (5),
Control the charging power supply (2) to charge the spare battery (6),
The main charging switch (4) is switched on and off in sequence to pulse charge the secondary battery (1) at the pulse charging timing, the main charging switch (4) is switched off and the charging power source (2) is pulse charged. The sub charging switch (7) connected to the secondary battery (1) is turned on, and the secondary battery (1) is charged by both the charging power source (2) and the spare battery (6). Charging device. 8. The charging device for a secondary battery according to claim 7, wherein a diode is connected between the sub charging switch (7) and the secondary battery (1). 9. The control circuit (3) detects that the secondary battery (1) is not attached and turns on the preliminary charging switch (5) to turn on the preliminary battery (6) by the charging power source (2). The charging device for the secondary battery according to claim 7, which is charged.