Simple nickel-cadmium battery charging device

Experience shows that fast charging of nickel-cadmium batteries cannot be achieved simply by increasing the current, because the large amount of gas and heat generated during the "fast charging" process will cause fatigue damage to the battery. If during the charging process of the battery, the charging is stopped for a short period of time, and then the battery is discharged with a large current, the various polarization phenomena inside the battery will quickly disappear, allowing the fast charging process to continue. The circuit introduced in this article is designed based on this idea.
　　working principle

 　　The circuit principle of the device is shown in Figure 1. 220V mains power is added to both ends of the primary coil of the power transformer T through the mechanical timer S, so an AC low voltage of about 15V is induced on the secondary coil. An avalanche trigger is formed by resistor R1, capacitor C and transistor VT. The power supply charges C through R1. When the voltage across C rises to the avalanche voltage of VT, VT turns on, causing the unidirectional thyristor VS to trigger conduction. As a result, a large current discharge of the nickel-cadmium battery is formed. In the second half of the cycle, VS is cut off, rectified by the diode VD, and R2 limits the current to charge the nickel-cadmium battery .