Here is the circuit diagram of simple battery monitor circuit. The main part of this circuit are the IC MN13811G from Panasonic and an efficient flasher circuit based on transistors Q1 (BC 558) and Q2 (BC 548). This circuit works in such a way that it produces a flash of LED when the output voltage of battery comes below a preset value.
In this circuit, the preset value of voltage is fixed at 2.4 volt. The circuit is designed in such a way that the IC is enabled when the output voltage of battery drops below 2.4 V. This enables the flasher circuit based on transistors Q1 and Q2 that drives LEDs and it flashes. One of the main advantages of this circuit is the power efficiency. This circuit draws a current of 1 uA when LED is not flashing and 20 uA when LED is flashing.
- Use a good quality PCB to assemble this circuit.
- This circuit here is an ideal one for monitoring the level of all types of 3V batteries.
- IC MN13811 series are available with different trip point voltages (from 2.4V t0 4.8V).
- Soldering iron must not be kept at the tip of IC’s pins for long time.