Here is a 12-volt automatic lead acid battery charger that shuts off the charging process once the battery attains full charge. The circuit will protect your lead-acid batteries from overcharging and increases life too.
Lets we discuss details about this DIY battery charger. Before you are going to build this circuit you need to know how Lead-acid batteries are getting charged. 12-volt lead-acid batteries need charging voltage of 14-15 volt ( pulsed DC voltage). And this voltage is considering as the full charge indication. The 12v battery full charge will be about 13.5 volt remaining in the battery. This voltage range is considering making an automatic cutoff circuit.
The low voltage cutoff is 11.5v is enough. The full charge cut off is 13.5v and low voltage charging at 11.5v.
Working of Circuit
The automatic circuit is working based on the Oscillator ic NE555. The ic and some components will be controlling the high voltage and low voltage charging. A voltage difference in Pin number 2 and Pin number 6 determines the on/off of connected relay.
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