The simplest battery level indicator

The most surprising thing is that the battery charge level indicator circuit does not contain any transistors, microcircuits, or zener diodes. Only LEDs and resistors connected in such a way as to provide an indication of the level of the supplied voltage.

Indicator circuit


Battery level indicator circuit

The operation of the device is based on the initial switch-on voltage LED. Any Light-emitting diode - this is a semiconductor device that has a voltage limit point, only exceeding which it begins to work (shine). Unlike an incandescent lamp, which has almost linear current-voltage characteristics, the LED is very close to the characteristics of a zener diode, with a sharp slope of the current as the voltage increases.
If you enable LEDs in a circuit in series with resistors, then each Light-emitting diode will begin to turn on only after the voltage exceeds the sum of the LEDs in the circuit for each section of the circuit separately.
The voltage threshold for opening or starting to light an LED can range from 1.8 V to 2.6 V. It all depends on the specific brand.
As a result, each LED lights up only after the previous one lights up.

Assembling the battery charge level indicator


Assembling the battery charge level indicator

I assembled the circuit on a universal circuit board, soldering the outputs of the elements together. For better perception, I took LEDs of different colors.
Such an indicator can be made not only with six LEDs, but, for example, with four.
The indicator can be used not only for the battery, but to create a level indication on music speakers. By connecting the device to the output of the power amplifier, parallel to the speaker. This way you can monitor critical levels for the speaker system.
It is possible to find other applications of this truly very simple circuit.
The simplest battery level indicator

Watch a video of the level indicator working and assembling


come back
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Comments (8)
  1. Gregory
    #1 Gregory Guests 16 November 2017 12:25
    7
    Current, through previous Light-emitting diode, will increase with increasing voltage and switching on the subsequent LED. Each subsequent resistor will turn on (via Light-emitting diode) in parallel to the previous one and the total (total) resistance in the circuit of the first LED will drop sharply, and the current will correspondingly increase. Instead of an indicator, this circuit will drain the battery. After turning on the next LED, the current through the first LED will exceed the maximum permissible current for this LED and it will simply burn out.
    1. Dimon
      #2 Dimon Guests 16 November 2017 13:10
      8
      This is what current needs to be passed through the circuit by a 1k resistor and Light-emitting diode, to Light-emitting diode burned out??? It needs a lightning strike! So don't make people laugh!!!
      Everything works great. Although it is better to install a button and periodically turn it on and check the charge.
      The author is a bastard!
      1. Guest Dmitry
        #3 Guest Dmitry Guests 14 October 2018 16:22
        2
        Tell me, for a lithium battery 18 volts at 4 LED how to calculate resistance so that the first one Light-emitting diode lights up at 13.5V, 15V 17V, and 20V
  2. Alexei
    #4 Alexei Guests 27 March 2018 14:10
    10
    The diagram in no way works as the author intended - it does not show the battery charge. This circuit can only roughly act as a voltmeter.
    1. LOLIk
      #5 LOLIk Guests November 15, 2019 08:33
      2
      So a voltmeter is an indicator for batteries, but what else?
  3. ali.bar60.
    #6 ali.bar60. Guests January 25, 2019 11:05
    0
    ...simple, intelligible, unobtrusive!!!
  4. Ivan
    #7 Ivan Guests 8 February 2019 22:22
    2
    what voltage is this circuit for?
  5. Guest Alex
    #8 Guest Alex Guests 17 April 2019 17:16
    4
    An indicator consisting of several chains of LED - resistor - Zener diode works much better. The ignition voltage can be adjusted by adding silicon or germanium diodes in the forward direction.