Make a simple electric car battery charger

The charger is a must-have for electric vehicles. It is necessary to make one as a spare or to replace the damaged original charger. The attached figure is a self-made electric vehicle battery charger circuit, which is easy to make and can meet the performance requirements. In the figure, B is a finished 220V/110V, 150W transformer. After the transformation, the 110V AC voltage is passed through R1 (current limiting) and then half-wave rectified by diode VD1 to a DC voltage of about 0.45×110=49.5V. The charger uses this voltage as the charging power supply.

During charging, since R2 and VD2 provide base bias for the adjustment tube V, V starts to charge the battery after it is turned on. As the charging time increases, the terminal voltage of the battery gradually increases. When it reaches the full voltage value, it will break through the voltage regulator tube VD4 circuit, and VD3 will light up; at the same time, the photocoupler IC is triggered to turn on. At this time, since the saturation voltage drop of the IC output tube after it is turned on is very low, it is equivalent to short-circuiting the V base-emitter, so V is cut off and stops charging the battery, thereby protecting the battery from damage due to overcharging. The purpose of VD4 in series with the bias in the circuit is to make the saturation voltage drop of the IC after it is turned on significantly lower than the bias voltage drop value of the adjustment tube V, so that V can be reliably cut off at this time. During production, a heat sink should be installed on the adjustment tube V.