Battery Voltage monitor

All rechargeable battery has their specific level of charging and discharging, they are likely to get damage if the battery voltage exceeds that level. Here is a simple circuit battery voltage monitor used to indicate the state of battery by monitor them.

The circuit of battery voltage monitor is fabricated and designed around an op-amp IC LM709 configured as comparator. Where bi-color LED is used as indicator and indicates three voltage level state of a 12V battery. Resistor R1 with potentiometer VR1 is used as potential driver of voltage monitor circuit.When voltage level rise above 13.5 volts, the output from IC₁ goes low as a result LED begins to emit RED light. Similarly, when the voltage fall below a preset level (10Volts) the output goes high and the LED start to emit GREEN light. Resistors R₃ and R₄ is used as current limiter of LED.


PARTS LIST

Resistors

R1 = 1 KΩ
R2 = 18 KΩ 
R3, R4 = 680 Ω 
VR1 = 10 KΩ (Potentiometer) 

Semiconductors

IC1 = LM709 
D1 = 1N4003 

Miscellaneous

B1 = 12V Battery 
LED = Bi-color LED