This is a simple DIY charge controller schematic posted in response to a request by one of our readers on our facebook page. The main component of this auto battery charger circuit is a 555 timer which compares the voltage in the battery. It turns ON the charger if the battery voltage is below the variable preset voltage (12 volt chosen here) and turns OFF the charger if the voltage reaches 13.8 volt. The battery charging voltage of the charger can be varied by adjusting the variable resistor.
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To understand the working of this 12 volt battery charge controller circuit you must have an idea of the internal diagram of 555. You can refer the pin out section at the bottom. You must also check charge controller using LM324 IC where you can find video demonstration too.
Automatic battery charger circuit diagram
- IC 555
- Transistor BC 548
- Diode (6A4 x5 ,1N4007)
- Zener diode (5.1V)
- LED (red, green)
- Capacitor 4700uF,25V
- Resistor (1K x 3,820,2x10E 10W)
- Variable resistor 10K
- Relay 12V,10A
- Transformer 230V/0-15,5A
- Positive terminal of the upper comparator of 555 is connected with reference voltage in order to turn OFF the charger if the battery charges above 13.8V.
- Reference voltage is obtained by connecting a zener dide in series with a resistor.
- If the battery voltage is greater than 13.8V, comparator output goes high and flip flop will be set. This turns OFF the transistor and the relay. For understanding relay working see How to connect relay: Relays working with animation
- If the battery voltage is below the preset voltage (set by us), lower comparator will reset the flip flop. This turns ON the transistor and the relay will switch to charge the battery.
- The recharge voltage (preset voltage) can set by varying the variable resistor.
- Power ON is indicated by a red LED and charger ON status is indicated by a green LED.