Simple NiMH battery charger circuit designed with few easily available components and it can provide constant voltage and current to the target 9 Volt NiMH battery. We know Nickel Metal Hydride batteries are called as NiMH battery this types of batteries are don’t self discharge quickly and provides maximum voltage and current in minimal size hence used in most hand held electronics device.
This circuit build with status indicator LED, here whenever the battery connected to charging and the output voltage is normal then LED1 starts to glow. If not then LED1 stays in turn off condition. This circuit is designed to give 150 milli amps output.
- Step down transformer (0-12V AC)
- Bridge Rectifier module or (1N4007 X 4)
- Transistor TIP125 (PNP)
- LED = 2
- Resistors 47Ω, 10Ω, 2KΩ, 1KΩ each one
- Capacitors 330µF = 2
- 9V NiMH battery
Construction & Working
Nickel Metal Hydride Battery or NiMH battery Requires Slow charging and limited charge current, Over current charging or Overflow charging makes Heat in NiMH battery.
Step down transformer is used to convert 230V AC supply into 12V AC supply and Bridge Rectifier module converts AC supply into DC supply and then C1 capacitor performs filter process, Darlington Transistor TIP125 (PNP) is connected in the positive supply line and this Transistor provides Current regulation and protects battery from over current charging. LED1 is connected between positive supply and base terminal of TIP125 followed by R1 Resistor and this LED indicates the presence of battery at the output and supply flow. LED2 is connected across output with R4 Resistor and its indicates the output DC supply.