Engineers Garage

  • Electronic Projects & Tutorials
    • Electronic Projects
      • Arduino Projects
      • AVR
      • Raspberry pi
      • ESP8266
      • BeagleBone
      • 8051 Microcontroller
      • ARM
      • PIC Microcontroller
      • STM32
    • Tutorials
      • Audio Electronics
      • Battery Management
      • Brainwave
      • Electric Vehicles
      • EMI/EMC/RFI
      • Hardware Filters
      • IoT tutorials
      • Power Tutorials
      • Python
      • Sensors
      • USB
      • VHDL
    • Circuit Design
    • Project Videos
    • Components
  • Articles
    • Tech Articles
    • Insight
    • Invention Stories
    • How to
    • What Is
  • News
    • Electronic Product News
    • Business News
    • Company/Start-up News
    • DIY Reviews
    • Guest Post
  • Forums
    • EDABoard.com
    • Electro-Tech-Online
    • EG Forum Archive
  • DigiKey Store
    • Cables, Wires
    • Connectors, Interconnect
    • Discrete
    • Electromechanical
    • Embedded Computers
    • Enclosures, Hardware, Office
    • Integrated Circuits (ICs)
    • Isolators
    • LED/Optoelectronics
    • Passive
    • Power, Circuit Protection
    • Programmers
    • RF, Wireless
    • Semiconductors
    • Sensors, Transducers
    • Test Products
    • Tools
  • Learn
    • eBooks/Tech Tips
    • Design Guides
    • Learning Center
    • Tech Toolboxes
    • Webinars & Digital Events
  • Resources
    • Digital Issues
    • EE Training Days
    • LEAP Awards
    • Podcasts
    • Webinars / Digital Events
    • White Papers
    • Engineering Diversity & Inclusion
    • DesignFast
  • Guest Post Guidelines
  • Advertise
  • Subscribe

Voltage Level Display of 12V Battery

By Dimpal Kumar Kalita March 1, 2012

The voltage monitoring of a 12V battery is especially necessary when a discharged battery is being charged. It may be for the batteries used with inverters in home or commercial batteries. Here is a simple project produced to monitor the battery voltage using 741 op amp. The Circuit Diagram is shown in Circuit Diagram Tab.
 
Generally a 12V battery is expected to produce a 12V dc voltage all the time until it gets discharged. Practically, it is not possible and the output voltage of the battery decreases gradually as load connected to it draws current from it. So it is generally considered that if the output voltage of a 12V battery changes from 12V to 9V approximately, it is constant and after the voltage falls below 9V, it is considered to be discharged and need to be charged again. Any inverter designed to use with a 12V battery should be comfortable to produce a constant AC output voltage during the fall of battery voltage from 12V to 9v approximately. My point to say all these is that to monitor a 12V battery, it is sufficient to monitor the battery voltage from 12V to 9V range and a voltage below 9V should give a warning for LOW BATTERY VOLTAGE. Here for the development of the circuit, the 12V to 9V range is divided into 6 parts as 9V, 9.5V, 10V…11.5V. So 6 op amps are used to compare and display the appropriate level of voltage. The circuit is simple. Comparison is done between the two terminals of each op amp and accordingly output is shown. The series of resistors connected at the inverting terminals of each op amp makes a voltage divider and exact comparing voltage is supplied to each op amp.
 
For example if the battery voltage is 10.7V, the upper 2 LEDs in the circuit will be OFF and the lower 4 LEDs will be ON. Similarly if the battery voltage is 9.2V only the LED at the bottom will be ON and other 5 will be OFF.
If the voltage goes down below 9V, the transistor will be activated and the buzzer will start indicating LOW VOLTAGE.
 
The value of the resistors is calculated as
Assume current ‘i’ flowing through the voltage divider is 1 mA. There should be six identical resistors across each op amp. Let the value of each resistor be R.
But we need to monitor voltage from 9V to 12V i.e. only 3V.So the extra 9V should be dropped across somewhere. Let it be resistor X.
Then (6*R + X)*1*10^-3 =12V
Let, R=0.5K
Then, X=9K
The power rating of the resistors should be above 2 Watt.
 
COMPONENTS
1.      Op Amp 741 [6]
2.      Resistor (5K6 [6], 0.5 watt)
3.      Resistor (0.5K [6], 9K [1], 2 watt)  (9K if not available may be split to three 3K )
4.      LEDs [6]
5.      Transistor (2N3906)
6.      12V Buzzer [1]
 
POWER SUPPLY
The power supply to the 741 op amp is unipolar 12V regulated DC.

Project Source Code

 

Circuit Diagrams

Voltage-Level-Monitoring


Filed Under: Electronic Projects
Tagged With: battery, display, voltage level
 

Next Article

← Previous Article
Next Article →

Questions related to this article?
👉Ask and discuss on Electro-Tech-Online.com and EDAboard.com forums.



Tell Us What You Think!! Cancel reply

You must be logged in to post a comment.

EE TECH TOOLBOX

“ee
Tech Toolbox: 5G Technology
This Tech Toolbox covers the basics of 5G technology plus a story about how engineers designed and built a prototype DSL router mostly from old cellphone parts. Download this first 5G/wired/wireless communications Tech Toolbox to learn more!

EE Learning Center

EE Learning Center
“engineers
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, tools and strategies for EE professionals.

HAVE A QUESTION?

Have a technical question about an article or other engineering questions? Check out our engineering forums EDABoard.com and Electro-Tech-Online.com where you can get those questions asked and answered by your peers!


RSS EDABOARD.com Discussions

  • Industrial Relay Board Design for Motorcycle Use
  • Finding past posts on edaboard?
  • I think i have devised a new type of "super_transformer" for the Electricity grid?
  • What is the purpose of this relay?
  • mosfet driver problem in regeneration mode

RSS Electro-Tech-Online.com Discussions

  • Pic18f25q10 osccon1 settings swordfish basic
  • Sump pit water alarm - Kicad 9
  • Anyone jumped from Easyeda std to Easyeda pro?
  • turbo jet fan - feedback appreciated.
  • More fun with ws2812 this time XC8 and CLC

Featured – LoRa/LoRaWan Series

  • What is the LoRaWAN network and how does it work?
  • Understanding LoRa architecture: nodes, gateways, and servers
  • Revolutionizing RF: LoRa applications and advantages
  • How to build a LoRa gateway using Raspberry Pi
  • How LoRa enables long-range communication
  • How communication works between two LoRa end-node devices

Recent Articles

  • How IoT network topologies work
  • The top five AI startups to watch in 2025
  • STMicroelectronics unveils SoC based on secure MCU
  • Nexperia’s 48 V ESD diodes support higher data rates with ultra-low capacitance design
  • Taoglas releases Patriot antenna with 18 integrated elements covering 600 to 6000 MHz

EE ENGINEERING TRAINING DAYS

engineering

Submit a Guest Post

submit a guest post
Engineers Garage
  • Analog IC TIps
  • Connector Tips
  • Battery Power Tips
  • DesignFast
  • EDABoard Forums
  • EE World Online
  • Electro-Tech-Online Forums
  • EV Engineering
  • Microcontroller Tips
  • Power Electronic Tips
  • Sensor Tips
  • Test and Measurement Tips
  • 5G Technology World
  • Subscribe to our newsletter
  • About Us
  • Contact Us
  • Advertise

Copyright © 2025 WTWH Media LLC. All Rights Reserved. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media
Privacy Policy

Search Engineers Garage

  • Electronic Projects & Tutorials
    • Electronic Projects
      • Arduino Projects
      • AVR
      • Raspberry pi
      • ESP8266
      • BeagleBone
      • 8051 Microcontroller
      • ARM
      • PIC Microcontroller
      • STM32
    • Tutorials
      • Audio Electronics
      • Battery Management
      • Brainwave
      • Electric Vehicles
      • EMI/EMC/RFI
      • Hardware Filters
      • IoT tutorials
      • Power Tutorials
      • Python
      • Sensors
      • USB
      • VHDL
    • Circuit Design
    • Project Videos
    • Components
  • Articles
    • Tech Articles
    • Insight
    • Invention Stories
    • How to
    • What Is
  • News
    • Electronic Product News
    • Business News
    • Company/Start-up News
    • DIY Reviews
    • Guest Post
  • Forums
    • EDABoard.com
    • Electro-Tech-Online
    • EG Forum Archive
  • DigiKey Store
    • Cables, Wires
    • Connectors, Interconnect
    • Discrete
    • Electromechanical
    • Embedded Computers
    • Enclosures, Hardware, Office
    • Integrated Circuits (ICs)
    • Isolators
    • LED/Optoelectronics
    • Passive
    • Power, Circuit Protection
    • Programmers
    • RF, Wireless
    • Semiconductors
    • Sensors, Transducers
    • Test Products
    • Tools
  • Learn
    • eBooks/Tech Tips
    • Design Guides
    • Learning Center
    • Tech Toolboxes
    • Webinars & Digital Events
  • Resources
    • Digital Issues
    • EE Training Days
    • LEAP Awards
    • Podcasts
    • Webinars / Digital Events
    • White Papers
    • Engineering Diversity & Inclusion
    • DesignFast
  • Guest Post Guidelines
  • Advertise
  • Subscribe