voltage comparator circuit
In the circuit having a voltage quad comparator (LM339) is used as a simple bar graph meter to indicate the state of charge 12-volt lead-acid battery acid. A 5 volt reference voltage is in each of the (+) inputs of four comparators and the (-) inputs are connected, each point is connected to a voltage divider. The LED lights up when the voltage at the negative (-)-input exceeds the reference voltage. Calibration can be by adjusting the 2K potentiometer so that all four LEDs illuminate when the battery voltage is 12.7 volts indicates a full charge with no 
load on the battery is done. At 11.7 volts, the LED should be made, and shows an empty battery. Each LED is a change of about 25% charge or 300 millivolts, so that 3 LEDs indicate 75%, 2 LEDs indicate 50%, etc.
The actual voltage on the temperature and battery type from, battery wet gel battery, etc . For more information on battery care.
2 Responses
Stay in touch with the conversation, subscribe to the RSS feed for comments on this post.
Arshed jan
BS Electronic Engineer
best circuit for making battery moniter as will as automatic battery charger.
Hello!
I’m thinking of building such a battery status monitor for a 12V battery. Unfortunately I know little about electronics. Can you explain how you can calculate the values of the rezistors in order to obtain specific voltage values at which the LEDs light up? Also, how much current is passing through the LEDs? I’m interested in finding out how much power is consumed by the whole circuit because I don’t want it to draw too much current from the battery. Thanks!