JPH02206334A - Method of charging chargable battery - Google Patents

Abstract

PURPOSE:To prevent a battery from deterioration caused by overcharge by measuring an ambient temperature of the battery with a temperature sensor, deciding optimum values of discharge finish voltage and a charging time, and charging only for a charging time after discharging to the final discharge voltage. CONSTITUTION:A switch 2 is turned OFF by a charge starting signal, and a battery 1 starts to discharge rapidly by a discharge current circuit 3. A charge preparation finish detector 5 detects a voltage drop to a final discharge voltage at a detected temperature by the information on the discharge current and a temperature detected by a temperature sensor 4. The switch 2 is turned on, the discharge current circuit 3 is separated to stop discharge, a timer 6 is set by the discharge stop information and the temperature detected by the temperature sensor 4, a switch 7 is turned off, and the rapid charge is started by a charge current circuit 8. When a setting time of the timer 6 elapses, the switch 7 is turned on, and the charge current circuit 8 is separated to finish the rapid charge.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to improvements in methods for charging rechargeable batteries, such as nickel-cadmium batteries.

(Prior Art and Problems to be Solved by the Invention) Recently, nickel-cadmium batteries have been widely used in various fields such as homes because they can be recharged and used many times and are inexpensive. Conventionally, charging methods for secondary batteries such as nickel-cadmium batteries include rapid charging methods and standard charging methods, which are classified based on the magnitude of charging current.

The quick charging method is a method of charging the battery with a large current several times the rated operating current of the battery, and while it can charge the battery in a short time, it may cause overcharging if the battery continues to be charged even after it is fully charged.
Gas is generated due to the decomposition of the electrolyte, and it becomes impossible for the cathode plate to absorb all of this gas, resulting in rapid deterioration of the battery.

The standard charging method is a method of charging with a small current equivalent to the rated operating current of the battery, and compared to the quick charging method, there is less risk of battery deterioration even if overcharged, but it takes longer to charge.

As a method to compensate for the drawback of the rapid charging method that there is a risk of battery deterioration during overcharging, there is a method of detecting a rise in charging voltage or temperature during rapid charging and terminating charging. However, this method determines the end of charging by detecting the difference in voltage and temperature from the voltage and temperature at the start of charging, so it is not an effective method when charging a battery that is close to fully charged.
There is a risk of battery deterioration due to overcharging.

In order to solve this problem, the idea was that if the battery is sufficiently discharged and the conditions are constant during charging, it can be fully charged in an approximately constant charging time, so after discharging the battery,
A method has also been proposed in which a timer is used to perform rapid charging for a certain period of time. However, the charging and discharging characteristics of nickel cadmium batteries are greatly affected by the ambient temperature, and even though the voltage at the end of discharging and the charging time also depend on the temperature, it is difficult to maintain a constant voltage at the end of discharging and charging time. Depending on the temperature, charging may start without sufficient discharge, or depending on the temperature, the battery may enter an overdischarge state, causing polarity reversal and accelerating battery deterioration. Furthermore, during charging, there is a risk that charging may be terminated without being sufficiently charged, or that charging may not be completed even in an overcharged state, leading to battery deterioration.

(Means and effects for solving the problem) The present invention has been made to solve the problems as described above. The present invention provides a battery charging method in which the optimal values of the discharge end voltage and the charging time are determined from the values, and after the battery is discharged to the discharge end voltage, the battery is charged for the aforementioned charging time.

When discharging using the above method, there is no over-discharging, and the discharge can always be made to a state close to a complete discharge.Also, the degree of discharge is always constant, and it is set in consideration of the influence of temperature. Since rapid charging is performed for the specified amount of time, sufficient charging can be achieved and overcharging can be avoided.

Furthermore, if the switch is made to trickle charging after the quick charging ends, the discharge due to self-discharge of the battery can be compensated for by trickle charging, and there is no risk of battery deterioration due to overcharging even if charging is continued.

(Example) FIG. 1 is a block diagram showing an example of a method for charging a rechargeable battery according to the present invention. In the figure, a secondary battery such as a nickel cadmium battery, that is, a rechargeable battery 1 is connected to a discharge current circuit 3 via a switch 2, and a temperature sensor 4 such as a thermocouple or thermostat is installed adjacent to the battery 1. It is provided.

When charging is to be started, a charging start signal is input from A. This signal closes the switch 2, and the battery 1 starts discharging rapidly by the discharging current circuit 3. Based on this discharge current information and the temperature detected by the temperature sensor 4, the charging ready detector 5 detects that the voltage has dropped to the discharge end voltage at the detected temperature, and this information is sent to the switch 2. The switch 2 is opened, the discharge current circuit 3 is disconnected, and the discharge is stopped.The timer 6 is set based on the discharge stop information and the temperature detected by the temperature sensor 4, and the switch 7 is opened.
is closed, and the charging current circuit 8 starts rapid charging. When the set time of the timer 6 has elapsed, the switch 7 is opened, the charging current circuit 8 is disconnected, and the rapid charging ends.

Note that the charging current circuit 8 and switch 7 function as a charging circuit and switch for only quick charging when charging is to be completed with only quick charging, and when performing trickle charging to compensate for self-discharge of the battery after completing quick charging, This is the charging circuit and switch used for both quick charging and trickle charging.

(Effects of the Invention) In the charging method of the present invention, since the discharge is performed by determining the discharge end voltage depending on the temperature, the degree of discharge can be kept constant regardless of the temperature, and the charging time can be adjusted depending on the temperature. Since this is done after setting, sufficient charging is possible regardless of the initial discharge level of the battery, there is no possibility of insufficient charging, and there is no risk of battery deterioration due to overcharging.
Also, since it can be charged quickly, charging time can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a method for charging a rechargeable battery according to the present invention. 1: Rechargeable battery, 4: Temperature sensor.

Claims (1)

[Claims] 1. In a charging method that completes charging by discharging a rechargeable battery until it reaches a set discharge end voltage and then charging it for a certain period of time, by detecting the ambient temperature of the battery, the discharge end voltage corresponding to this temperature is determined. and a method for charging a rechargeable battery, comprising: detecting an optimal value for a charging time, discharging to the above-mentioned discharge end voltage, and then performing rapid charging during the above-mentioned charging time.