Li - Ion Battery Level Indicator





Introduction: Li - Ion Battery Level Indicator

Are you looking for a simple circuit to measure your Lithium Ion single cell charging and discharging level? Here is one chip circuit, powered up from the same Lithium Ion battery you want to measure.

This circuit is design to measure 3.7V rechargeable batteries level.

4.2V - 100%; 4V - 80%; 3.8V - 60%; 3.6V - 40%; 3.4V - 20%


D1 is used to protect a circuit from the battery being placed wrong way. You can use 1N4007 or something similar.

When this circuit was simulated on LTSpice, I used R1 value 18k, however, after this circuit was soldered on a printBoard, this value was to high, so i had to change it to 15k. It might be because of inaccuracy of the other resistor values.

LM339 datasheet:

The circuit for 12V battery level indicator was found on

but with the changes was made to measure 3.7V batteries.


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I have a 3s3p battery pack 18650 and i have a voltage meter as well. If i understood correctly the instructions, it should be like this:

20% 40% 60% 80% 100%

10,2V 10,8V 11,4V 12V 12,6V

(3*3.4) (3*3.6) (3*3.8) (3*4) (3*4.2)

Am I Correct?

I think this doesn't work without a zener diode because the battery voltage changes and the reference voltage too

yep, thats what I think, too... Aaaaand, yes, the original 12V version used a zener... This circuit is useless.. :(

Hi , This is very useful, can you please send PCB design and schematic at Or post it here itself

need a circuit which shows battery level during charging, for charging purpose consider a simple nokia lion bat charger which produce around 5 V

Will it work for li-ion battery pack in 4S?

Don't resistors only limit current? And doesnt the - on the comparators change as battety voltage drops?

Anyway to get more accurate readings to my arduino? I want to be able to tell percantage

PCB Please :)

hello....can i use it in 7.4v circuit?? if not...then any suggestions.... NEED HELP..

is there any way i can regulate the margins of voltage that the leds are working? meaning, when i put it on a simulator, it works for voltages 3.7V to 4V. is there any formula to calculate the R1 and R2 or any other resistors needed for a lower margin 2V to 4.8V?