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  • Automatic 12V Battery Charger

  • Created: Apr 26, 2016

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There are some people that are in habit of plugging their batteries at night before going to sleep. An overcharged battery causes overheat and shortens the lifespan. To stop from overcharging, an Automatic 12v Battery charger will automatically prevents the battery to charged when it is full.

The circuit composes of two parts (power supply and the load comparison). The power supply is composed of main supply voltage of 230V and stepped down by a center tapped transformer to a 15-0-15V. The output of the transformer is being rectified by D1 and D2 to convert AC voltages to a DC voltage. The noise from the DC voltage is being filtered out by the 470uF capacitor. The output of the capacitor DC voltage is regulated through LM317T. From the adjust pin of LM317T, the voltage is varied by the RP1 10k. The output is applied to the battery through D3 and R5. The zener diode D6 conducts when battery is fully charged and the base of Q1 gets the current through the zener diode so that the total current is grounded. The red LED indicates the battery is fully charged and green LED indicates that the battery is charging.

This circuit protects the battery from overcharging. It automatically shut off to prevent from overcharging. It is useful especially for gadgets such as smartphones, laptops, etc because people love to charge their gadgets overnight.



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