Here is a battery monitor circuit which can be used to monitor the voltage of 12V lead acid batteries such as car batteries. The circuit is built around the LM3914 IC and some external components with 10 LEDs which will indicate the voltage level. Two equipment are required for adjusting the
circuit for 12 volt battery, one is lab power supply and second is digital volt meter. First you have to connect the digital volt meter to the pin 4 and pin 6 of the IC and adjust the variable resistor VR2 for a reading of 1.2 volts and make VR1 and VR3 on their center settings now if the span between VR1 ends equal to 4.5V then the circuit is ready to use.