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I have an aging Gateway NX560XL laptop. The battery is toast and a new one, even aftermarket, starts at $130. So, to experiment, I began tearing apart the old battery to see what can be done. I found it used 8 standard size 18650 Li Ion cells arranged two cells parallel then in series (like: ====). Some online shopping revealed ~$7-13/ea replacements depending on mAh output. My plan is to load test to determine the bad cells and replace only those, as I read that typically only 1 or 2 may be bad.

I'm proficient with soldering, however these cells are attached with welded tabs. Some of them broke during disassembly and I'm not sure how to reattach them. What I found online are cells like these that have solder tabs pre-welded to the ends so I can solder wires onto.

Is there any guide available that provides the instructions and parts to do this kind of rebuild?

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up vote 9 down vote accepted

Typically, the batteries are connected to each other via spot welded tabs. You could solder wires to the batteries you found, but it might not fit afterwards. Make sure you use a wire with enough current carrying capacity (i.e. 14 AWG). Theses batteries do get hot and pass a lot of current during peak loads. You can also build yourself a spot welder rather cheaply if you want to try this route.

Make sure the case is well closed after your repair. Epoxy should do the trick.

There are a few tutorials on the web as well.

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Actually, the tab that broke is at the strap that connects 2 cells together side-by-side, not at the end of the cells. Looks like I'm just going to solder a short wire to hold them together, unless there are better ways to repair tabs. – spoulson Jul 15 '09 at 12:51
Silver conductive epoxy should work but I have not tried this. You should also consider that the epoxy is expensive (40$ per syringe). – JcMaco Jul 15 '09 at 12:59
You will want to use cells with the same capacity as the original, and replace them all, not just some. Replacing some cells with different capacity will cause the weaker ones to drag down the whole pack, and possibly cause reverse discharge of the others, ruining them quickly. Even if the replacements have the same stated capacity, the old one will have less capacity due to their age. – psusi Dec 26 '12 at 4:11
This is so dangerous that you should not be encouraging him to do it! – techaddict Oct 3 '14 at 3:36

Beware: Soldering Li-ion cells can be somewhat dangerous, as when they get hot such as during soldering they can tend to explode.

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resulting in potentially imminent DEATH! – techaddict Oct 3 '14 at 3:35

Unless you have experience with electronics and soldering I wouldn't risk it. Batteries put together incorrectly have an unhealty disposition to extreme exothermic reactions (i.e. blow up) which can be quite fatal if you are close.

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