This battery tester circuit is designed using the LM3914 integrated circuit and some electronic components. Battery voltage is compared with a reference voltage obtained from an internal source. Reference voltage (pin 8) can be set between 1.5 V and 2.7 V, R1-R2-P1. Potential voltage pin 8 be the head scale LED string. This means that if the voltage is 1.5 V, each LED will symbolize a voltage of 150 mV. We recommend setting the reference voltage from 1.5V NiCd battery, 2.0 V for dry battery. The resistor R1 sets a current of 12.5 mA for each LED.