Repairing Any laptop battery - Li-Ion cell replacement

Written By: Damien Leflon

Comments: 9

Repairing Any laptop battery - Li-Ion cell replacement

Difficulty

Moderate

Steps

Time Required

50 minutes

Introduction

We are going to identify dead cells in battery packs and replace them.

Beware - This tuto is higly experimental, Li-Ion cell present fire / explosion / burn hazards this guide is for educationnal purpose only and should not be reproduced without safety measures. Remember to always wear apropriate PPE and work in appropiate environment.

Tools

Multimeter

Step 1

Caution: Lithium-ion batteries can catch fire or explode if they are damaged or short-circuited—especially when they are charged. Be extremely careful not to bend them or short-circuit them with your probes.
Battery pack works by putting individual cells in parallel / series. Each cell has a nominal voltage / capacity and they are put together to give the whole battery pack it's global voltage / capacity.
Here we have a 3s2p battery pack. This means that you have 3 serial attached blocks of 2 parallel cells.
The lefmost block seems dead, the cells reads a steady 0 volts on my multimeter.
The 2 other block show ~3.6 V which means they are still alive, great !
I haven't tested individual cells from the 2 working blocks for a good reason. This battery pack has been stored for several monthes, if only one cell in the block was dead, the other (good) one would have discharged in it until it also dies ( which is what must have happen in dead block )

How to know if what 18650 mah will you use? Like for my scenario, my laptop is 2,800 mah and I have 4 18650 inside, so each battery is 700mah. Can I use higher mah?

jhun -

Step 2

Here I have 2 scrap 18650 cells form another dead battery pack. They are still charged but I have no fear has the battery electronics will balance the charge levels later.
After this step, reassemble the pack and everything should be fine.
Remember that this a dirty fix and you should consider the repaired battery pack as NOT SAFE

As you say, putting loose batteries together is potentially dangerous.

When testing 18650 lithium (3.7v) batteries, it is best to set your multimeter to 9v battery test mode (they may appear to be charged during a normal DC voltage test, but still worthless).

Charge your batteries and let them rest for a day or two. If the batteries have lost none of their charge, only then should they be considered healthy.

Before mounting them, place them parallel for at least a day, to equalize the Electromotive Force (EMF)).

Exception: Modern battery packs and their chargers charge each cell individually.

Homer 82

Delrue Dominique - 23/04/20

Conclusion

Pour réassembler votre appareil, suivez les instructions dans l'ordre inverse.

Author

Damien Leflon

Member since: 27/12/15

643 Reputation

7 comments

Salut, je pense changer toutes les cells dans ma batterie de laptop morte. J’ai actuellemt 6 x Samsung 26H. Est ce que je peux installer plus puissant ? Des LG HG2 18650 3.7v 3000mAh 20A High Drain Flat Top par exemple ? pour augmenter en duree et de vie de la batterie de mon laptop. Merci.

Red B - 25/12/17

Bonjour Red B

Je ne sais pas comment fonctionne votre chargeur de batterie

CC (courant constant), CV (tension constante) ou CC-CV (tension constante avec courant limité).

Le premier (CC) prendra un peu plus de temps pour charger votre batterie.

Le HG2 est également un millimètre plus grand que le 26H.

Ci-joint deux liens vers leurs fiches techniques.

http://grobotronics.com/images/companies...

https://www.18650batterystore.com/v/file...

le HG2 est légèrement plus robuste que le 26H.

Bonne chance;

Homer 82

Delrue Dominique - 24/04/20

What will be considered a clean fix?

dkorablev -

Sir, usually battery packs are hermetically sealed with glue, though it is not impossible to open the case. Still, it is time-consuming to separate the two plastic portions of the case. Kindly suggest how quickly I can open the battery pack and oblige. Often BMS is faulty kindly advise whether the BMS are interchangeable?

Best Regards

Dr P K Maitra BHILAI, INDIA dipalyconsultants@hotmail.com

dipalyconsultants -

Hello.

I don't have any experience yet, but I've found out that you can open the involucre that seals the battery with banana oil.

Leandro -

Sir, usually battery packs are hermetically sealed with glue, I have opened the battery pack successfully & found it inside 4 nos 21710 cylindrical batteries and one BMS> All are Made in China & spot welded and the pack is connectable with 6 pin socket as usual. Please suggest how to connect the batteries since I don’t have at the moment the spot welding machine.

kind regards

Dr P K Maitra BHILAI, INDIA dipalyconsultants@hotmail.com

dipalyconsultants -

Just a bit too vague. We would like to understand why cell sharge at different rates, hoes the battery need to be reset upon first power up, and what is your recommended bonding/ wire guage method. I do appreaciate for your time and enthusiasm.

Erik Oosterbaan -