all four comparators to monitor four different voltage stages of a battery. For monitoring the voltage of any battery it is essential to know the full and half voltage of a battery. For example you want to monitor a 12V battery, a 12V full charge battery will show 12.6V after few hours of removing it from the charger. When the battery is 50% used it will show 12.1V on the multimeter. It is always better to charge the batteries when they are 50% empty.
For tuning this battery monitor circuit a variable power supply will be required. For monitoring 12V battery set 12.5V in variable power supply and connect it in the place of battery in the circuit. Now slightly adjust the VR1 until the LED1 goes ON. After this set 12.4V in the variable supply and slightly adjust the VR2 until the LED2 goes ON. Now set 12.3V in variable supply and slightly adjust VR3 till the LED3 goes ON. At last set 12.1 in the supply and adjust the VR4 until the LED4 goes ON. After these adjustments one again check the all the LEDs by increasing the variable supply voltage to 12.6V and again lowering it slowing. After these settings the circuit will be ready to use.
Here is a project of a battery monitor circuit using LM339 IC. The circuit can be used to monitor any type of batteries from 6V to 12V. The heart of the circuit is a LM339 IC, LM339 a comparator IC, contains four separate totally independent voltage comparators.
In this circuit we have used
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