LM324: Precision Battery Voltage Indicator

In this tutorial, we are making a project on a Car Battery Monitor with Low Battery Cutoff Function. This circuit monitors the battery of any vehicle and shows a visual indication of the battery level through the four LEDs. It also contains a low battery cutoff function. This function will disconnect the vehicle’s battery with an electrical appliance when its battery level is at 50%, this will save it from deep/full discharge.

Working Explanation of the Battery Level Indicator

We are using an LM324 IC. This IC has four independent operational amplifiers. All of these are working as a separate comparator in this circuit to detect the specific voltage level of the battery. These voltage levels are set through variable resistors of 10K. Each op-amp has a variable resistor connected to its input. LEDs are used for visual indication of battery levels.

Circuit Tuning for a 24V Battery

• Take a variable power supply and set 25.8 because a 24V battery shows nearly 26V or 25.8V in DMM when fully charged.

• Connect this power supply in the place of the battery in the circuit.

• Adjust VR1 until LED1 turns off.

• Change the voltage of the power supply to 25.4V and adjust the VR2 until LED2 turns off.

• Change the voltage of the power supply to 25 now and again adjust the VR3 until LED3 turns off.

• Now for the last level set 24.5V in the power supply and adjust VR4 until LED4 turns off. At this point, the transistor will turn off too and deactivates the relay which is connected with the battery and the headlights.

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