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LED VoltMeter Circuit

Here is a Simple LED Voltmeter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four level LED indicators.

The nominal terminal voltage of a Lead Acid battery is 13.8 volts and that of a Tubular battery is 14.8 volts when fully charged. The LED voltmeter uses four Zener diodes to light the LEDs at the precise breakdown voltage of the Zener diodes. Usually the Zener diode requires 1.6 volts in excess than its prescribed value to reach the breakdown threshold level. When the battery holds 13.6 volts or more, all the Zener breakdown and all LEDs light up. When the battery is discharged below 10.6 volts, all the LEDs remain dark. So depending on the terminal voltage of the battery, LEDs light up one by one or turns off.

Schematic of the LED VoltMeter Circuit

22 Comments

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  • Ashlum

    Dear D.mohankumar,

    what do u mean by the word ‘R’ next to the resistor resistant value?

    150R…does it mean 150 Ohm?

  • D.Mohankumar

    Thanks for pointing out the error in the diagram.Unfortunately an extra line appeared.It is corrected.

  • anonymous

    Hmm I am not saying the idea with all the Zener diodes is bad – just trying to point out that the schematic might be badly drawn – What you do according to that schematic is you short circuit the battery. the whole current will go via this wire and not through the leds, zeners and other.

  • D.Mohankumar

    Try and see the result

  • anonymous

    Isn’t it so that the most right wire will short circuit the whole thing and thus no leds will ever light up ?

    • Sebastian Kushero

      This is a simple and clever circuit without the use of expensive components. works perfectly made this 3 years ago and still works well . we use it with a push button switch in our Solar Charge controllers as Battery indicators

      The use of the Capacitor is not needed as has no reason to be there .
      Red Lights from 8 to 10.5 V
      Orange lights from 11.7 to 12 V
      Yellow above and the Green above 13.5

      Kits available

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