JPH06165403A - Charging method of nickel-cadmium battery - Google Patents

Abstract

PURPOSE:To obtain such a nickel-cadmium battery as there is no deterioration in capacity even if it is directly charged in any using state of discharge depth less than 100% by charging it with pulse current having 1Hz to 10MHz of frequency in the case of charging. CONSTITUTION:When a nickel-cadmium battery is charged with a continuous direct current in a state less than 100% of discharge depth, charging and discharging efficiency is greatly lowered with the production of the dendrite to greatly decease initial capacity, and when charging is made with pulse current having 1Hz to 10MHz of frequency, the production of the dendrite is controlled even if it is directly charged. As a result, the lowering of charging and discharging efficiency is eased to control memory effect, and battery capacity is not decreased even it repetitive charging and discharging is made. In addition, the effect of pulse current is decreased in a frequency region less than 1Hz of frequency of the charging pulse current, and when charging is made in a state less than 100% of discharging depth, the battery capacity is decreased. Even in a frequency region exceeding 10MHz, a life characteristic is deteriorated with the decrease of battery capacity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for charging a nickel-cadmium storage battery, and more particularly to a method for charging a nickel-cadmium storage battery charged by a pulse current.

[0002]

2. Description of the Related Art In recent years, due to remarkable progress in electronics, it has become possible to reduce the size, weight, and power consumption of electronic devices, such as cordless devices such as camera-integrated VTRs, book-type, notebook-type, palm-type personal computers, and portable devices. Is rapidly spreading. As a power source for these devices, the demand for nickel-cadmium storage batteries has grown remarkably and is most widely used.

A nickel-cadmium storage battery uses a nickel compound as a positive electrode active material and a cadmium compound as a negative electrode active material, and is rapidly demanded in a wide range of fields due to its excellent discharge characteristics, storage recovery characteristics, life characteristics and high reliability. Is expanding. On the other hand, as applied equipment is becoming smaller and lighter, one of the demands from the market is that nickel-cadmium storage batteries are also required to be smaller and lighter, and at the same time have higher performance such as higher capacity and shorter charging time. Has been strongly requested.

[0004]

However, the nickel-cadmium storage battery has excellent life characteristics when it is repeatedly charged and discharged at 100% depth many times, but it is charged when the discharge depth is less than 100%. And has a drawback called the memory effect that the initial battery capacity is greatly reduced. Since the cause is not clear, the charging conditions for nickel-cadmium storage batteries are strict as a countermeasure, and it is indicated that 100% discharge is performed before charging when using as a usage condition, or the charger itself has 1
A charger with a built-in discharge circuit at a depth of 00% is used as a countermeasure.

In order to solve the above-mentioned problems, the present invention does not cause a capacity deterioration even when directly charged in a nickel-cadmium storage battery having a depth of discharge of less than 100% in any use state, and does not have a so-called memory effect. It is an object of the present invention to provide a charging method for a nickel-cadmium storage battery.

[0006]

In order to achieve the above object, the present invention is characterized in that a pulse current is used for charging a nickel-cadmium storage battery. That is, while the nickel-cadmium storage battery is usually charged with a continuous DC current, in the present invention, charging is performed with a pulse current having a frequency of 1 Hz to 10 MHz, so that the discharge depth is 10
It is intended to provide a method for charging a nickel-cadmium storage battery which has less capacity deterioration, that is, a memory effect which is extremely small even when the nickel-cadmium storage battery of less than 0% is directly charged, and which has excellent life characteristics.

That is, the present invention is a method for charging a nickel-cadmium storage battery, which is characterized in that charging is performed by a pulse current having a frequency of 1 Hz to 10 MHz during charging.

[0008]

[Function] Normally, nickel-cadmium storage batteries are charged
A continuous direct current is used, but in this case, the morphology of deposition on the negative electrode during charging is non-uniform and dendrite formation occurs. In particular,
By charging in a state where the depth of discharge is less than 100%, the behavior becomes prone to occur remarkably, so that the charge / discharge efficiency due to dendrite formation is remarkably reduced, and as a result, the initial capacity of the nickel-cadmium storage battery is remarkably reduced. It causes a reduced memory effect.

On the other hand, the charging method of the nickel-cadmium storage battery of the present invention has a frequency of 1 Hz to 10 M.
By charging with a pulse current of Hz, even if a nickel-cadmium storage battery with a depth of discharge of less than 100 is directly charged, dendrite generation during charging is suppressed, and as a result, a decrease in charge / discharge efficiency is alleviated and a memory effect is achieved. Is suppressed, and the battery capacity does not decrease even after repeated charging and discharging.

In the charging method of the nickel-cadmium storage battery according to the present invention, the frequency range of the pulse current to be charged is set to 1 Hz to 10 MHz. Here, the frequency of the charging pulse current is set to 1 Hz to 10 MHz.
In the frequency region below Hz, the effect of pulse current decreases,
Depth of discharge 1 as in the case of continuous DC current charging
When the battery is charged in a state of less than 00%, the so-called Lee effect of reducing the battery capacity is observed.

Further, even in a frequency range exceeding 10 MHz, the life characteristics are deteriorated as the battery capacity decreases. By applying the charging method as described above to a nickel-cadmium storage battery, it is possible to obtain a nickel-cadmium storage battery having excellent life characteristics without causing a memory effect.

[0012]

EXAMPLES Examples of the present invention will be described below.

[0013]

Example 1 A positive electrode substrate was a sintered nickel positive electrode mainly composed of nickel hydroxide, and a negative electrode substrate was a paste type cadmium negative electrode mainly composed of cadmium hydroxide.
Wrap in a spiral through a nylon non-woven separator,
An electrolytic solution containing potassium hydroxide as a main component was added and the mixture was sealed. A closed type nickel-cadmium storage battery equivalent to a AAA type and 180 mAh was prototyped, and a battery capacity test and a charge / discharge cycle test were conducted.

Using this battery, a charge / discharge cycle test was conducted under a condition of shallow discharge depth to test the degree of capacity deterioration of the battery due to repeated charge / discharge. Charge / discharge cycle conditions are 18 mA and 180 mA at 20 ° C.
The initial state is a fully charged state with a capacity of 100% at a current of, and a discharge depth of 50% at a current of 36 mA (discharge time 2.
After discharging for 5 hours, the consumed discharge capacity is 10 mA at 10 mA.
A cycle of 0% charge was performed 50 times, a discharge depth of 50% was discharged at a current of 36 mA (discharge time 2.5 hours), and a cycle of 100% charge of the consumed discharge capacity was performed at 180 mA. The charging current at this time is a pulse current, and the frequency is 1 Hz, 500 Hz, 500 KHz, 10M.
It was carried out at a duty ratio of 50% at Hz. Table 1 shows the battery capacity after the above cycle test, and the capacity deterioration rate when the initial capacity obtained from the values of the initial battery capacity and the battery capacity after the cycle test is 100%.

[0015]

[Table 1]

As a comparative example, Table 2 shows the battery capacity and the capacity deterioration rate when a charge / discharge cycle test was conducted at the same current value at a discharge depth of 50% and 100% charge.

[0017]

[Table 2]

FIGS. 1 and 2 show the relationship between the number of cycles and the capacity deterioration rate when a cycle test is conducted under the above conditions.

[0019]

[Example 2] A sealed nickel-cadmium storage battery equivalent to 180 mAh of AAA type prototyped in Example 1 was used to perform a charge / discharge cycle test using pulse currents having different duty ratios. First, a 100% charged battery was discharged with a current of 36 mA at a discharge depth of 50% (discharge time 2.5 hours), and the consumed discharge capacity was charged 100% at 180 mA, which was repeated 50 times. The conditions for discharging are frequency 5KH
z, duty ratio 10%, 25%, 50%, 75, respectively
%, The capacity after 50 charge / discharge cycles was measured, and the ratio with the initial capacity was measured to obtain the capacity deterioration rate. Table 3 shows the value of the capacity deterioration rate when the duty ratio of the pulse charging current is different.

[0020]

[Table 3]

As described above, Table 1, Table 2, Table 3 and FIGS.
As is clear from the results shown in Fig. 3, by charging with a pulsed current, it is possible to use a battery that does not have a capacity deterioration, that is, a memory effect, even if a nickel-cadmium storage battery with a depth of discharge of less than 100% is directly charged. Shows that the life characteristics of the battery are remarkably improved.

[0022]

As described above, when the nickel-cadmium storage battery according to the present invention is charged, a pulse current having a frequency of 1 Hz to 10 MHz is used to charge the nickel-cadmium storage battery. It has become possible to provide a nickel-cadmium storage battery that has excellent life characteristics and does not produce a memory effect even when repeated direct charge / discharge is performed on the cadmium storage battery.

[Brief description of drawings]

1 a pulse current according to the invention (pulse current 18 m
The characteristic view which shows the relationship between the number of charge / discharge cycles and the capacity deterioration rate of a battery at the time of charge by A). Note that the characteristics due to DC charging are also shown in the figure.

FIG. 2 shows a pulse current according to the present invention (pulse current 180 m
The characteristic view which shows the number of charge / discharge cycles at the time of charge by A), and the relationship of the capacity deterioration rate of a battery. Note that the characteristics due to DC charging are also shown in the figure.

Claims (1)

[Claims] 1. A method for charging a nickel-cadmium storage battery, wherein charging is performed by a pulse current having a frequency of 1 Hz to 10 MHz during charging.
How to charge a cadmium battery.