JPH05199674A - Method for charging battery - Google Patents

Abstract

PURPOSE:To prevent the occurrence of running away of heat of a floating- charge type battery by using a charger having constant-voltage and constant- current outputting characteristics by switching the set value of the charging current to a smaller value upon discriminating a fully or nearly fully charged state of the battery. CONSTITUTION:A load 4 is driven by rectifying AC power supply 1 by means of a charger 2 of a constant-voltage and constant-current system and, at the same time, a floating battery 3 is charged by supplying a DC output to the battery 3. A charging current detection circuit 5 detects the charging current and inputs the detected current value to a charging control circuit 6. The circuit 6 starts counting time from the commencement of the charging by means of a timer incorporated in the circuit 6 and switches the charging current to a second charging current having a small value when the counted time reaches the one corresponding to the fully or nearly fully charged state even when the battery 3 is in a deeply discharged state. The second charging current is set at the self-discharging current value or higher in accordance with the capacity of the battery 3 or ambient temperature. Therefore, running away of heat from the battery can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a floating charging type DC power supply device comprising a charger and a storage battery, which is capable of safely charging the storage battery.

[0002]

2. Description of the Related Art A conventional method for charging a floating charging type DC power supply device will be described with reference to FIGS. FIG. 4 is a block diagram of the floating charging type DC power supply device. In FIG. 4, a charger 2 converts the AC voltage of the AC power supply 1 into a DC voltage corresponding to the floating charging voltage of the storage battery 3, charges the storage battery 3 in a floating manner, and supplies electric power to the load 4. A charging current detector 5 is composed of a shunt resistor, a Hall element current detector or the like, and detects the charging current of the storage battery 3 and inputs it to the charging control circuit 6. The charging control circuit 6 charges the storage battery 3 according to the set constant voltage / constant current characteristic. Here, when the AC power supply 1 cannot supply electric power due to a failure such as a power failure, DC power is continuously supplied from the storage battery 3 to the load 4.

When the AC power supply 1 is restored after the storage battery 3 is discharged in this way, or when the storage battery that has been deeply discharged for some reason is charged, the charging current of the storage battery 3 is determined by the charging current detector 5. The constant current charging is performed according to the charging current setting value that is detected and preset by the charging control circuit 6. In this case, the charging current set value is generally set to a larger value in order to shorten the charging time.

As described above, in the floating charging type DC power supply device, as shown in the time chart of FIG. 5, constant current charging is performed at the current value I ₁ at the initial stage of charging, and constant voltage charging is performed as the charging progresses. After the transfer, the charging current gradually decreases.

[0005]

However, in the prior art as described above, when the floating charging voltage is inappropriately high or when the ambient temperature of the storage battery 3 rises for some reason, the broken line in FIG. As shown in the figure, there is a problem that a phenomenon called heat escape occurs in which the charging current once decreases and then increases again after shifting to constant voltage charging. Further, not only immediately after recovery charging but also in a charging state due to a minute current at the end of charging, gas generation increases inside the storage battery due to the external factors as described above, and this phenomenon may occur.

If this phenomenon occurs, the temperature of the storage battery 3 further rises due to the increased charging current, and in the worst case, the storage battery 3
Deterioration and burning. Therefore, an object of the present invention is to provide a charging method capable of safely charging the storage battery 3 without causing thermal runaway.

[0007]

In order to achieve the above object, according to the present invention, charging of a floating charging type DC power supply device comprising a charger having a constant voltage and constant current output characteristic and a storage battery connected to the output of the charger. In the method, it is determined that the charging current setting value of the charger is switched to the smaller second charging current setting value by determining whether the battery is fully charged or a state close thereto.

Specific means for determining whether the battery is fully charged or close to it are as follows: a method of using a timer to start timing from the start of charging, a method of detecting that the charging current has dropped to a predetermined value, a charging current time There is a method of detecting that the rate of change has become zero.

[0009]

In the present invention, by switching the charging current set value to the smaller second setting value, the charging current of the storage battery in the fully charged state or a state close to the same is limited, and the situation in which the storage battery runs out of heat is avoided. To be done.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a charging method for a floating charging type DC power supply device according to the present invention will be described with reference to FIG. In FIG. 4, the charging current of the storage battery 3 at the initial stage of charging is detected by the charging current detector 5 and controlled by the charging control circuit 6 to, for example, about 0.1 C amperes. Here, the time counting is started from the charging start time, and even if the storage battery is in a deep discharge state, the charging is completed by the timer included in the charging control circuit 6 that finishes the time counting in a time in which the battery can be fully charged or close to it. The charging current set value of the device 2 is switched to the smaller second charging current set value. The second charging current setting value is set to a charging current value which is equal to or larger than the self-discharging current value of the storage battery 3 and which does not cause thermal runaway determined by the capacity of the storage battery 3, ambient temperature, etc., for example, 0.01 C amperes. Further, the set time of the timer is set to about 24 hours in consideration of the charging efficiency of the storage battery.

Next, the operation of the embodiment of the present invention will be described with reference to the time chart of FIG. From the start of charging to time T ₁ , the storage battery 3 is charged with a relatively large charging current I ₁ (for example, about 0.1 C ampere). The storage battery voltage rises as the charging progresses, and when time T ₁ elapses, the storage battery 3 shifts to constant voltage charging by the floating charging voltage. After that, the charging current gradually decreases, and finally the charging is continued with a minute current.

Thereafter, the charging current set value of the charger ₂ is switched to the smaller second current set value I ₂ at the time T _{2 at} which the timer ends. At this time, since the storage battery 3 is already fully charged or in a state close to it, the charging current has a value of I ₂ or less, and even if the charging current set value is switched, the charging current does not change at all.

In this state, if the charging current increases for some reason, the charging current becomes equal to the second charging current setting value I ₂ at time T ₃ and is limited to this value, so that a current exceeding that value is exceeded. Does not flow, and thermal escape of the storage battery 3 can be effectively prevented.

The operation of the second embodiment of the present invention will be described with reference to the time chart of FIG. In the first embodiment of the present invention, a timer is used to determine the state of full charge or a state close to that. In the second embodiment, this state is determined by detecting the charging current. In FIG. 2, before the time T _1, the operation is the same as that of the first embodiment, the constant current charging is performed with the current of I ₁ , and after the time T _1, the constant voltage charging is started. Here, at time T ₂ when it is detected that the charging current gradually decreases with the progress of charging and becomes equal to the smaller second charging current setting value I ₂ preset by the charging control circuit,
The charging current setting value is switched from I ₁ to I ₂ . Subsequent operations are the same as those in the first embodiment, so the description thereof will be omitted.

Next, the operation of the third embodiment of the present invention will be described with reference to the time chart of FIG. Similarly to the second embodiment, the third embodiment also uses the charging current to determine whether the battery is fully charged or is close to it. In FIG. 3, before the time T _1, the operation is the same as that of the first embodiment, and the constant current charging is performed with the current of I ₁ , and after the time T _1, the constant voltage charging is performed. As the charging progresses, the charging current gradually decreases, and the time change rate (di / dt) of the current gradually approaches zero from a large negative value. Here, at time T ₂ when di / dt = 0, the charging current setting value is switched from I ₁ to I ₂ .
Subsequent operations are the same as those in the first embodiment, so the description thereof will be omitted.

[0016]

As described above, according to the present invention, it is possible to safely charge a floating charging type DC power supply device without causing thermal runaway of a storage battery, and the effect is great.

[Brief description of drawings]

FIG. 1 is a time chart showing an embodiment of a charging method of the present invention.

FIG. 2 is a time chart showing a second embodiment of the charging method of the present invention.

FIG. 3 is a time chart showing a third embodiment of the charging method of the present invention.

FIG. 4 is a block diagram of a floating charge type DC power supply device.

FIG. 5 is a time chart showing a conventional charging method.

[Explanation of symbols]

 1 AC power supply 2 Charger 3 Storage battery 4 Load 5 Charge current detector 6 Charge control circuit

Claims (1)

[Claims] 1. A charging method for a floating charging type DC power supply device comprising a charger having a constant voltage / constant current output characteristic and a storage battery connected to the output of the charger, and judges whether the battery is fully charged or close to it. A method of charging a storage battery, comprising switching the charging current setting value of the charger to a smaller second charging current setting value.