Failed Lithium battery, can we fix it?

I can hear very common question over and over again: I have not working device and I think this is because of old Lithium battery inside. I opened it and please help me to change it!

Here is a general instruction for this:

1. Identify how to open failed device and carefully take it apart. Ones you see the battery, you could figure how to remove it. Please note: sometimes removing battery can lock up the device PCBA in "failed" mode.

2.Remove battery. Sometimes there is a connector, but very often you have to unsolder or even cut tabs or wires off. Please cut or unsolder ONE wire at the time! Cutting all 2-3 battery wires in one shot may cause battery explosion.

3. Take a look at battery markings. Normally battery model consists of few letters and 6 digits. Normally those digits identifies the battery dimensions. For example the FlirOne infrared camera has LF602035. In this case you could guess 6mm x 20mm x 35mm.

Sometimes manufacturer choose to switch numbers. Because of this I advise to take calipers and measure the battery actual size. If you are lazy to do this step, please don't bother to read the next passage. This procedure is not for you. Also please do not send us pictures of your battery. a. This is your "project" b. We most likely will ask you to simply ether tell us OUR battery model or at least the SIZE of the battery.

4. You need to troubleshoot the old battery a. Voltage is supposed to be above 3V. If it is 0V, it is junk. But here you have to measure voltage on the cell tabs (not on the wires from PCM). Obviously if voltage on wires is above 3V, no need to get to battery tabs. But if 0V is on the wires, it is not exactly the sign of 0V on the tabs.

In order to get to bare tubs, you have to unwrap the PCM small board (see the step 5).

If we see over 2.9V on the tabs, this may be a good candidate for recharging and continue to use it. Although I have to tell you the secret: each time you go below 3V, you taking around 5-10% battery capacity out.

5. To get to battery tabs, you have to use sharp blade or knife and cut carefully the capton yellow tape, which keeps the PCB (or PCM) small board on the battery lip. Be careful not to cut the battery itself.

Sometime instead of cutting tape, you may be able to unwrap it.

6. If it is obvious to you, the battery is bad, you have to get a replacement. If you can't find identical size, you may try slightly bigger or smaller. Usually designers use the maximum possible battery size that fits in the battery allowed space. But sometimes smart designers give a little more space to fit even bigger sizes.

Please do not approach us with the question about capacity. If you think for example the written old capacity is 100mAh and you found only 90mAh in the same size and that bothers you, please stop the project and toss your device to the nearest garbage bin. You must understand the law of sacrifice: if you wish to have at least functional device back to life, you must be prepared it will function 10...10% less time on one charge.

Life in general is full of those tests for "law of sacrifice". If you not ready for it, there will be a tough struggle ahead of you.

We have very nice part filtering applet on our web and you could very fast to find out if we even remotely have something to what you looking for as of size wise.

8.  If your old battery has pcm and we (or someone else) don't have a protected battery available, you could always take a bare cell battery and solder the old pcm module on the new battery cell.

For this you have to:

Unwrap the pcm module (see the step 5 above) if it wasn't done for measurement and carefully cut tabs of failed battery from the PCM.

9. Then you going to solder new bare cell on top of PCM module in the places, where the old tabs use to be. Please always ether take a picture of old battery or draw the sketch or mark with colors the polarity of old battery on those small tails of tabs, which will be left on pcm.

10. Not it is the time to take a fresh Kapton tape or even just a scotch tape and isolate with one layer the PCM module. Then you could carefully fold the PCM back to battery lip place and put another layer of tape. Normally it is little bulging on the lip, but with gentle squeeze with your fingers, you could make PCM module more compact on top of the battery.

11. At this point you may check voltage on wires and give it a slight charge (or even full charge ) with external charger. Please do not go above 1C rate on the first charge.

Here is the FlirOne camera before and  after total substitution of bare cell.


As you can see, the original battery LF602035 (or possibly LF-602035) was with 3 wires. Third wire is normally comes from thermistor. There was no way I could have find the identical battery. Also as you can see, the new battery was a bare cell GM622238, which is 6.2mm x 22mm x 38mm. The new battery bare cell was by 2...3 mm bigger on two dimensions and by 0.2mm thicker. I was struggling to convince the remanufactured battery to get back to allotted space in the camera. But finally the persistence won. Camera functioned as new and even better... But we going to run a separate report on this repair case as of good example how to do it.

Again, please understand: this article is written for readers entertainment and if you loose your valuable property in the process of YOUR project, we do not carry any responsibility.

Also please be reasonable: Your hobby project or device problem is not our top priority and very often we may not have a few spare samples for sale. Our main branch always happy to serve you on one or two paid samples via web orders. But we may not have an exact size. Nagging and telling about your important project in case if we don't have them in stock, considered as a childish behavior. Please use automated web sales channel. Calling or emailing on a few samples is not nice act on our system. Sorry, we don't have enough sales people to answer small size hobby deals. For extra questions please use Forum information channel. We will try to answer there if there is no one else to help you there.

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