circuit to  automatically charge your desired battery. The two variable resistors VR1 and VR2 are used in the circuit to set start and stop the charging process on the desired voltage of the battery.

Tuning or adjusting the circuit for your desired battery requires an adjustable power supply. Let say you want to charge a 6V lead acid battery, the fully charge voltage of a 6V lead acid battery is 7.3V while charging after charging is stoped its voltage will slowly come to 6.3V. Now first of all connect the adjustable power supply in the place of power supply and do not attach any battery in the circuit. Now set 7.3V in the adjustable power supply and adjust VR2 until the LED1 become activated. Next set the power supply voltage to 5.9V and adjust VR2 until the LED3 goes OFF. The same procedure can be done for 12V battery except the start and stop points. Like a 12V battery become fully charged when it shows 14.5V while charging so the stop point should be 14.5V and start point should be 11.9V. You can also use the same procedure for other batteries.

The relay switch can also be connected to mains plug of the power supply so it will switch ON the whole charger circuit from the mains when the battery requires charging and switch it OFF when the battery is fully charged. This trick can save a lot of power. The LEDs use in the circuit will show different indications, When the battery is fully charged LED1 will become activated indicating that the battery is full charged. The LED4 shows the battery under charge.

The circuit is fully automatic therefore can be leaved with a battery to start charging automatically when the battery voltage falls. For example you can leave it connected to a 12V battery and set the charge start point to 12.5. This will take care of self discharge battery and start charging it automatically when the battery voltage falls below 12.6V.

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This smart battery charger will take care of your rechargeable battery and will automatically start charging when your battery voltage falls on the preset level. The circuit can be used to charge wide variety of rechargeable batteries of different kinds and voltages. A simple tuning is required to set the


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Smart Universal Automatic Battery Charger Circuit Diagram