Battery Level Indicator

Category: Education

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Battery Level Indicator:

Battery Level Indicator


Introduction An Battery level detector is a device, circuit that is used to check the remaining life of a battery. This circuit let us easily recognise the battery level. It uses Five LEDs in all. So if any LED glows, it indicates battery capacity.

Circuit Diagram:

Circuit Diagram

Components Used:

Components Used

Circuit Description:

Circuit Description D1 is the voltage reference zener . Tied to this is a string of divider resistors (R2-6) that set the various fixed voltage levels. R7 & R8 form a voltage divider to that reduces the battery voltage by a factor of 3. U1 is an LM339 quad comparator that compares the various voltages from the two dividers.

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The comparator sections have open collector outputs that simply function as switches to operate the LEDs. D7 protects against reverse battery connection. The LEDs are biased to operate at about 4mA which is quite bright if modern LEDs are used. This current can be adjusted simply by varying the series resistors.


Working If the battery voltage is above 12 volts (that is the normal terminal voltage of 13.8), Zener conducts and Green LED lights and Red LED remains off. If the battery voltage is below 12 volts, Zener remains non conducting and Green LED remains off and Red LED lights. When the battery is connected to the charger, and if the battery is accepting charge, Green LED goes off and Red LED remains on .

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When the battery attains full charge, Green LED lights and Red LED goes off. If the battery is not accepting charge, Green LED never lights, even after the prolonged charging. This indicates that the battery is not attaining the normal terminal voltage above 12 volts.


Advantages It is used to check the battery level with the help of LED’S. For eg . if three LEDs glow, it indicates battery capacity of 30 percent .and if 10 LEDs glow then it is 100 percent.

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