WTS - Li-ion battery 10-levels fuel gauge - limited quantity


Being unable to find the right li-ion battery fuel gauge, I decided to build one myself.
I don’t want to keep a voltmeter with me everywhere I go and try to guess the level of my battery according to it.
Also I figured some people might be interested too.

Here is the device

Dimensions are 30mm x 18mm
Thickness of the board itself (without the LED bargraph) is 5mm.

(I voluntary left some edges around the board that can be cut out if needed)

The device provides 10 levels, from 4.2v on max to about 3.4v on min.
So each graduation is about 0.080v.
It draws about 2.2mA per LED, so in full it will draw 10x2.2mA = 22mA.
I tried to make it as small as possible.

You can choose between 4 different colors for the LEDs: BLUE, GREEN, YELLOW, RED

(More like amber)


- If 10 levels is too big, I can provide a 5 levels device

  • I can sell it without LED bargraph, you just have to connect regular LEDs on it, and the board actually will be smaller.

Possible Usage

- You can integrate it to your charger, and see the gauge going up while charging (I will show you a Xtar WP2 II with this device incorporated when I have time)

  • Or you can use a simple 18650 battery box for example (on 1 side the device, on the other side the battery)

$19 + shipping.
Payment with Paypal.

Or $15 face to face (Bay Area, CA)

I don’t have stock for the LED bargraph and I don’t want to keep stock, so I will proceed by batch.
For now I can only make 8 (number of IC left I have)

It will take about 2 weeks for me to receive the parts and build it.

If you are interested let me know the LED color you want.


Looks very interesting. Waiting to see the final product and the external dimensions. Nice work!

Nice! What size is that?

I still am waiting for my new PCB so I can use smd, I should receive it this week.
The size will be about 30mmx18mm and thickness 5mm for the board, without the LED bargraph.

The LED bargraph is the “biggest” part and the thickness will be added on top of it

If the LED bargraph is too big for you, I can sell just the board, and you can use regular smaller LEDs.
Also I can make a 5-levels board, so that you only have to use 5 LEDs.

I just ordered some components, so I think the quantity will be limited to 8.

Alright I updated the post with the picture and the dimensions.

Oh, I thought more people would be interested in a li-ion level meter :open_mouth:

I think most people here are willing to make their own so they can have one with a number read out.

Its to expensive… Thais the Point.
If you buy a voltmeter from china, you can get a better performance for less…

I respect your work and will to share this but check this out http://www.ebay.de/itm/Mini-DC-0V-To-99-9V-Red-LED-Digital-Panel-Volt-Voltage-Meter-Voltmeter-/290717802952?pt=LH_DefaultDomain_0&hash=item43b021a1c8#ht_3833wt_952

Yeah… I am not chinese with large quantity of components, and $2 is barely the price of a LED bargraph…
I can reduce the price, but $2 don’t think about it.
The device is smaller, and more readable than just a voltage, that’s the point I stated at the beginning.
I updated the price.

Home made for under $10.

Yeah this is a voltmeter, this is just not the same.

The spectrum led battery meter costs $30.

So, it’s just the meter with two loose wires you have to manually hold onto while the battery is rolling around?

You dont get it…
Thats ok.

I will show you an integration of 2 of these devices into a WP2 II soon.

Not interested people please leave the topic in peace. Thank you.

I don’t get the difference? If the task is to find out the battery status than you can have this for a few bucks. There are a lot of such meters out there you have to compete with.

Like yours, it’s made for nimh but in 4.8v mode could work:

You see there are a lot out there, so it would be better to take one of these very cheap ones because they are in every detail better. Also a modification of one of the Chinese meters would make more sense than build a crappy thing up.

Sorry for opening your eyes but you have to see everything in context…

Guys if you want to discuss this type of thing do it in another thread. This is a sales thread NOT a discussion thread.

Silicon, sorry for my part in this.

This one is from 4.8v to 6v, doesnt work with 1 li-ion battery.

Thanks scaru.

No I Don’t, but I want to. I just need something more visual so I can see it in application. I’d like to see how it connects and works with a wP2 myself, and maybe it’s integration with a battery carrier. I’m not knocking it, I just want to see more detail pics of its usage and installment. I wouldn’t mind having something that shows me charging status on my SP2 while its running. Mine is just a voltage meter for testing after the fact. Would it be complicated for me to install? Help me out here.

Essentially what you would have to do is dissasemble the charger and then solder two wires onto the positive and negative. Then you have the wires lead out of the charger and mount the board wherever you want to.

I will show you some pics soon.
Before doing that I checked the whole internet to find the right one, none of them was what I was looking for.
The reasons I did this are,

- The device assesses from 3.3v/3.4v to 4.2v, which is the best range to check li-ion batteries, not from 3v to 4.2, etc. (I can configure it to change the range also, or for 2 batteries, etc…)

- It is small enough to be included in battery chargers.

- I can configure it to have 10 levels or 5 levels, which makes it smaller to integrate in battery chargers.

  • I can implement 1 indicator for each slot in my WP2 II.