USB-Powered NiCd-NiMH Battery Charger

Simple USB-powered battery charger for a single 1.2V NiCd (nickel-cadmium) or NiMH (nickel-metal hydride) rechargeable battery.

The input power source of this charger circuit board is 5V 1A from the mini-USB port and the charging output is 1.2V 125mA, which can be easily charged the batteries.

It is only suitable for NiMH/NiCd rechargeable batteries.

Circuit Diagram

Schematic of USB-powered 1.2v NiCd/NiMH battery charger circuit shown below.

Components Used

The following components are used in this circuit board.

1. Mini-USB female port (1 pcs)
2. R1: 24 resistor (1 pcs)
3. R2: 1K resistor (1 pcs)
4. D1: 1N4007 diode (1 pcs)
5. D2: 3mm Red LED (1 pcs)

Circuit Explanation

The charging circuit is simple and uses fewer components.

Here, the DC supply voltage (5volt) taken from the mini-USB port, the red LED connected with the R1 resistor is to indicate the supply, R2 resistor drops the input voltage & current, and the Diode D1 protects reverse polarity supply, take extra care on battery polarity while connecting with this circuit board.

The charger gives 4.9V 175mA output without load at 5V 1A input, if we connect a single 1.2V 1000mA capacity cell, the charging power will drop to 1.2V 125mA, and the battery will charge completely safely within 5hr (approx).