Skip to content
Electronic Circuits

DIY Hobby projects, diagram, schematic

Electronic Circuits

DIY Hobby projects, diagram, schematic

Simple Battery State Indicator

electronicecircuits, September 17, 2009August 19, 2023
simple battery state indicator

Simple Battery State Indicator Circuit

Many a time the outdoor audio or video recording becomes imperfect due to a ‘dying’ battery. If the battery voltage is less than 9V for a 12V recorder, the output during playback will not be of a good quality due to variations in the motor speed.

Many car owners take their battery for granted, rarely giving it the maintenance required. As the winter nights advance the demands made on this vital power source increase. Combined with the inevitable aging process and diminishing ability to store a charge for a  long period, this makes the requirement of a simple aid to monitor battery voltage continuously obvious.

Simple Battery State Indicator circuit

PARTS LIST
R11 KΩ
R28.2 KΩ
R3470 Ω
R41 KΩ
R58.2 KΩ
D19V 400mW
D2LED YELLOW
D3LED RED
D45.1V 400mW
D5IN4001
D6LED GREEN
D712V 400mW
D8IN4001
Q1BC 148B
Q2BC 148B

The indicator was therefor designed to forestall any incipient failure by providing ‘at a glance’ information on battery state with three coloured LEDs.
Green indicating a battery voltage adequate for normal use,
Yellow that the voltage was fairly low and
red that the cell was dead.

When the battery is in top condition, its output voltage will be around 13V and, of course, even higher if recently charged. This potential is applied via D8 through R4, D7 and R5 to the base of Q2. This turns Q2 on, causing D6 to illuminate via R3. At this time Q2 effectively places a short circuit across the rest of circuit via D6, preventing D2 and D3 from emitting light.

As the battery voltage becomes lower,Q2 begins to turn off as the threshold of D7 is reached.This allows D2 to conduct as Q1 has all the time to be turned on via R1, D1 and R2. (D5 increases the voltage required for turning on D2 when T2 is on.) The current thus drawn via R3 precludes D3 from illuminating as the potential across it and D4 is not above the zener level.

Eventually, at still lower battery voltage, Q1 will turn off in the same way as Q2, allowing potential at the junction of D2, D3 and D6 to rise in excess of 5V zener level of D4 which begins to pass current and illuminates D3.

Zener diodes may be selected for other switching points and / or battery voltages.


Please send your ideas, those are very important for our success…

Electronic Circuits Battery ChargerIndicator CircuitsMeasuring CircuitsMeter Circuits

Post navigation

Previous post
Next post

Comment

  1. Pingback: Becoming a Video Game Tester

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

  • Diagrams
  • Privacy Policy
  • Software
  • Contact

Recent Posts

  • LM317 CONSTANT CURRENT CALCULATOR
  • 5V buck converter – LM2576 simple DIY project
  • ICL7107 PANEL METER
  • Precision 1Hz clock generator circuit
  • Toggle to Momentary Switch Using 555 Monostable

Categories

  • Circuit Tutorials
  • Electronic Circuits
  • Electronic Software

AC Projects Alarm Circuits Amplifier Circuits Amplifiers Antenna Circuits Battery Charger Calculator software Circuit Designer Control Circuits Converter circuits Crossover Circuits Data Sheets Digital Circuits Electronic Switch Flasher Circuits Game Circuits IC Programmer IC Programming Indicator Circuits LED Circuits Light Circuits Logic Circuits Measuring Circuits Meter Circuits Microchip Motor Circuits Music Circuits Oscillator Circuits PCB Designer PIC Power Amplifier Power Guard Power Supply PreAmplifier Circuits Radio Circuits Regulator Circuits Regulator Diagrams Regulator Schematics RF Schematics Sensor Circuits Tester Circuits Timer Circuits Transmitter Circuits Tutorials Vacuum Tube

©2025 Electronic Circuits | WordPress Theme by SuperbThemes