Li - Ion Battery Level Indicator

Intro: 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%

LED1 - RED; LED2 - YELLOW; LED3 - YELLOW; LED4 - GREEN; LED5 - GREEN

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: http://www.onsemi.com/pub_link/Collateral/LM339-D...

The circuit for 12V battery level indicator was found on http://www.electroschematics.com/6868/12v-battery...

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

Comments

[LenarOX]

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

[Relaf]

I agree with jntan.
A diode too (a LED in this case) can work as a regulator.
Being forward biased, it regulates the voltage to its forward voltage (~2V) as opposed to reversed biased zener diodes which regulate to their reverse biased voltage (zener voltage). This works.

[jntan]

The LED1 works as a voltage regulator because the forward voltage is ~2V in a wide range of forward current through it. A zener isn't necessarily needed here.

[gsmhack]

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

[WalterC77]

LED1 shouldn't be there, it should be a zener instead. otherwise a lot of current gets wasted through the led (and there would be no reference). A better reference should be added with something like a MAX6029, and resistors adjusted accordingly; the original circuit was made to test out lead acid batteries, which are much more powerful (and less sensitive) than puny lithium cells.

[jchristakis]

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?

[jchristakis]

nevermind my previous comment. i m so nab i totally missed to consider kirchoff's laws.... i am designing the pcb now . message me anyone for a copy if you want it.

[OlebogengS]

Please email me the PCB and the circuit design @ [e-mail]

[acidkidd]

Please sendme the PCB design Thank you

[e-mail]

[ChochoR]

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?

[rahuldj]

Hi , This is very useful, can you please send PCB design and schematic at [e-mail]? Or post it here itself

[leodemon]

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

[gaurav_23]

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

[kamhagh]

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

[Vitor HugoC]

PCB Please :)
[e-mail]

[SubhodipM]

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

[FatihF2]

hi i try it in Proteus program and its working but when its 3,7 v its all led are on but they are dim and when giving more then 3,7 v until 4,2 its just all leds is on and just giving more brightness. why is that

[DejfM]

Hi, can you pls send me schamatic? [e-mail] thank you very much

[MoezT]

can you send me pcb secheme ,[e-mail] ,i release the circuit in

BREADBOARD

but wan't work

[FahmiN4]

Could I get the PCB Scheme? Send to my email : [e-mail]