12V Car Battery Charger circuit

Posted on Feb 5, 2014

The following circuit diagram is the battery charger for your 12V car battery. Unlike other battery chargers, this circuit featured overcharging protection which automatically disconnect the charging circuit. Most car battery chargers are simple devices that continuously charge the battery with a few amperes for the duration it is ON. If the charg

 12V Car Battery Charger circuit
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er is not switched OFF in time, the battery will overcharge, its electrolyte lost due to evaporation, and its plate-element will likely be destroyed. The circuit above will eliminate these problems by monitoring the battery`s condition of charge through its retroactive control circuit by applying a high charge current until the battery is completely charged. When charging is complete, it turns on the red LED (LD2) and deactivates the charging circuit. This circuit is drawn to charge 12V batteries ONLY. Certain emphasis should be taken when wiring up this circuit. They are the connections of the transformer to the circuit board, and those supplying current to the battery being charged. These connections should be made with cables having a large cross-sectional area to prevent voltage-drop and heat build-up when current flows through them. Adjust TR1 to null value and charge the battery using the hydrometer technique (if you do not have or do not know how to use a hydrometer, then use a good condition battery and charge). Carefully adjust TR1 so that LD2 begins to turn ON and the charge current falls to a few hundred milliamps (mA). If TR1 is set correctly then in the next round of charging you will noticed LD2 begin to flicker as the battery is being charged. When battery is completely charged, LD2 turns ON completely. TR1 does not need further adjustment anymore. Q1 is connected in line with the battery and is fired by R3,...

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