JP3421404B2 - Rechargeable battery charging method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery charging method for charging the secondary battery while gradually decreasing the charging current value each time the battery voltage of the secondary battery reaches a predetermined voltage, and more particularly, The present invention relates to a secondary battery charging method capable of optimally setting a protection timer time for preventing overcharge of a secondary battery.

[0002]

2. Description of the Related Art As is well known, secondary batteries such as nickel-cadmium batteries and nickel-hydrogen batteries which can be repeatedly charged and discharged detect a full charge of the secondary battery by a -ΔV detection method or a peak voltage detection method. Although the charging is stopped, overcharging will occur unless a full charge is detected due to some abnormality.

In order to avoid such a risk of overcharging, normally, even if the above-mentioned fully charged state is not detected, the protection timer time is set so that the charging is forcibly ended after a predetermined time has elapsed from the start of charging. Is provided. This protection timer time can also be set appropriately in accordance with a secondary battery (for example, a secondary battery having a different capacity), as disclosed in Japanese Patent Laid-Open No. 4-88836.

[0004]

As described above, the protection timer time for protecting the battery to be charged can be set appropriately according to the type of the battery to be charged, but during charging When the charging condition (particularly, the charging current value) is changed, it cannot be said that the function of the protection timer time can be sufficiently fulfilled.

That is, when the charging current is reduced during charging, the charging speed thereafter is naturally slower than before, and there is a possibility that the protection timer time will elapse before full charge is detected. Therefore, if the protection timer time is lengthened from the beginning, such a problem does not occur, but the function of the protection timer time does not work effectively, which may lead to overcharge of the secondary battery.

[0006]

According to the present invention, the secondary battery is charged while the charging current value is gradually reduced every time the battery voltage of the secondary battery reaches a predetermined voltage, and the secondary battery is fully charged. When a preset protection timer time elapses before is detected, in the charging method of the secondary battery, the charging of the secondary battery is stopped, and each time the charging current value is decreased, the protection timer time at that time is reduced. It is characterized by resetting the remaining time of.

[0007]

In the present invention, the secondary battery is charged while the charging current value is gradually reduced each time the battery voltage of the secondary battery reaches the predetermined voltage. Here, when the charging current is decreased, the remaining time of the protection timer time at that time is reset based on the decrease rate.

Then, when the full charge of the secondary battery is detected, or when the protection timer time elapses before the full charge is detected, the charging of the secondary battery is stopped.

[0009]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention. 1 is a rechargeable battery such as a nickel-cadmium battery or a nickel-hydrogen battery, 2 is an alternating current from a commercial power source,
A charging power source for supplying a desired DC current to the battery 1 to be charged,
Reference numeral 3 is a charging control unit arranged between the charging power source 2 and the battery 1 to be charged, and converts the direct current from the charging power source 2 into an arbitrary charging current in response to the battery voltage of the battery 1 to be charged. It is converted and supplied to the battery 1 to be charged. In this embodiment, the battery 1 to be charged is
Each time the battery voltage reaches the predetermined voltage V0, the charging current value is gradually reduced in the order of I1, I2, I3 (where I1>I2> I3). Reference numeral 4 is a voltage detection circuit for detecting the battery voltage of the battery 1 to be charged, 5 is an arithmetic circuit composed of a microcomputer, 6 is a timer circuit for counting a protection timer time from the start of charging the battery 1 to be charged, 7 is an LED and The display circuit includes the drive circuit and displays the end of charging of the battery 1 to be charged.

FIG. 2 is a flow chart showing the operation of the first charger of the present invention, which will be described below with reference to the waveform chart of FIG.

In step S1, it is determined whether or not the battery 1 to be charged to be charged is attached. Charged battery 1
When is attached, rapid charging is started in step S2. In this embodiment, the constant current value I1 = 1C and the protection timer time T0 = 100 minutes are set as conditions for this rapid charging, and these conditions are set in the charge control unit 3 and the timer circuit 6 by the arithmetic circuit 5, respectively. .

In step S3, it is detected whether the battery 1 to be charged has reached full charge. This is performed by the well-known −ΔV detection method or the peak voltage detection method based on the battery voltage of the battery 1 to be charged detected by the voltage detection circuit 4. If it is determined in step S3 that the battery has reached full charge, the charging is stopped in step S6,
The display circuit 7 displays that the full charge has been reached.

On the other hand, when full charge is not detected in step S3, it is detected in step S4 whether the battery voltage of the battery 1 to be charged has reached the predetermined voltage V0. If the predetermined voltage V0 is not reached, it is determined in step S5 whether or not the protection timer time T0 (100 minutes in this case) set in the timer circuit 6 has elapsed. When the protection timer time has elapsed, step S6 If the charging is stopped and the time has not passed, the process returns to step S3.

If it is determined in step S4 that the battery voltage of the battery 1 to be charged has reached the predetermined voltage V0 before the protection timer time T0 has elapsed, in step S7,
It is determined whether the charging current is reduced to I3. Since the charging current is now I1, the charging current is reduced from I1 to I2 (that is, 2 / 3C) in step S8, as shown in FIG.

Next, in step S9, the remaining time T1 of the protection timer time (that is, the first set time T0-
The elapsed time Ta until the charging current is reduced to I2 is calculated. Then, in step S10, the remaining time T
1 is divided by the decrease rate of the charging current, and the result is reset in the timer circuit 6 as the protection timer time T0. That is, if the elapsed time Ta is 70 minutes, the remaining time T1 = 30 minutes set in the timer circuit 6,
In step S10, 30 minutes / (2/3) = 45 minutes is calculated, and the 45 minutes is reset in the timer circuit 6.

After that, the process returns to step S3, and the battery 1 to be charged is charged with a constant current I2 until a full charge is detected. After that, without full charge being detected,
When the battery voltage of the battery 1 to be charged reaches the predetermined voltage V0 in step S4, the process proceeds to step S7 through step S7.
8, the charging current is I2 to I3 (ie 0.5C)
Is reduced to.

Also in this case, as in the previous case, the remaining time T1 of the protection timer time (that is, the reset time T0-the elapsed time Ta until the charging current is reduced to I3) is calculated in step S9. . Then, in step S10, the remaining time T1 is divided by the rate of decrease of the charging current, and the result is set again in the timer circuit 6 as the protection timer time T0. Now, assuming that the elapsed time Ta is 20 minutes, 25 minutes / (3/4) = 33 minutes are set again in the timer circuit 6.

Thereafter, the process returns to step S3, and the battery 1 to be charged is charged at a constant current with the charging current I3 until full charge is detected. Then, when full charge is detected or when the timer time set in the timer circuit 6 has elapsed in step S5 after step S4, the process proceeds to step S6 and the charging is stopped.

As described above, in the present embodiment, the protection timer time, which was initially set as 100 minutes, finally becomes (70 minutes + 20 minutes + 33 minutes) = 123 minutes, which is the protection timer before full charge. It is prevented that charging is stopped over time.

In this embodiment, if the battery voltage of the battery 1 to be charged reaches the predetermined voltage V0 without full charge being detected in the charging after the charging current is reduced to I3, step S6 Go to and automatically stop charging.

[0021]

According to the present invention, each time the battery voltage of the secondary battery reaches a predetermined voltage, the secondary battery is charged while gradually decreasing the charging current value, and the full charge of the secondary battery is detected. In a secondary battery charging method in which charging of the secondary battery is stopped when a preset protection timer time elapses before being performed, each time the charging current value is reduced, the remaining protection timer time at that point Since the time is reset, the optimum protection timer time can be set at any time in response to changes in the charging current value, charging stops before full charge, or the protection timer time does not work effectively, The secondary battery can be charged optimally and safely without overcharging the secondary battery.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 3 is a waveform diagram showing the operation of the embodiment of the present invention.

[Explanation of symbols]

1 Charged battery 3 Charge control unit 4 Voltage detection circuit 5 arithmetic circuit 6 timer circuit

Claims (2)

(57) [Claims] 1. The secondary battery is charged while the charging current value is gradually reduced each time the battery voltage of the secondary battery reaches a predetermined voltage, and the preset value is set before the full charge of the secondary battery is detected. In a method of charging a secondary battery, which stops charging of the secondary battery when a predetermined protection timer time has elapsed, every time the charging current value is decreased, the remaining time of the protection timer time at that time is reset. And a method for charging a secondary battery. 2. The rechargeable battery charging method according to claim 1, wherein the resetting is performed so as to be substantially inversely proportional to a rate of decrease of the charging current value.