In this tutorial, we are making a good quality LM324 Battery monitor. You can make this circuit by using an LM3914 IC but that costs more than this IC, therefore we made an alternative circuit that works perfectly and costs less.
LM324 is an IC that consists of four independent low-power op-amps. All of which are used in this circuit. LEDs are connected with each op-amp for the visual indication. This circuit is easy to build and can monitor batteries with different kinds and voltages.
Hardware Components
Battery Monitor Circuit
| S.no | Component | Value | Quantity |
|---|---|---|---|
| 1. | Battery | – | 1 |
| 2. | IC | LM324 | 4 |
| 3. | LED | – | 4 |
| 4. | Resistor | 10K, 680 | 1, 4 |
| 5. | Variable Resistor | 10K | 4 |
| 6. | Zener diode | 3V | 1 |
LM324 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of LM324
Battery Monitor Circuit
Working Explanation
Each op-amp in this circuit is working as a comparator separately to monitor a specific voltage of the battery being monitored. This voltage is set by variable resistors. In this circuit, we are using a variable resistor of 10K at the input of each op-amp.
Circuit Adjustments
Before using this circuit needs some tuning and requires a variable power supply. Replace the battery of the circuit with this power supply. If you were using a 6V battery then set the voltage of the power supply to 6V. adjust the VR1 until LED1 turns off. Now change the voltage of the power supply to 6.1V, and again adjust the VR2 until LED2 turns off. Now change the voltage of the power supply to 6.2V and adjust the VR3 until LED3 turns off. Now for the final voltage level set 6.25V in the power supply and adjust VR4 until LED4 turns off.
After these settings check all the voltage levels again by increasing the voltage to 6.3V in the supply and then lowering it slightly to make sure that all the LEDs are turning ON/OFF at their specific level. The same procedure will be followed for other batteries. A battery should be recharged when 50% capacity is left to save it from deep or complete discharge, so the voltage levels should be set according to it.
