It's often not easy, either. It very much depends on the battery and the used controller. Make sure to always have enough voltage on the controller, since it might shutdown on power loss, leaving you with a battery with '0.0Wh capacity', regardless of the new cells. Also, some battery packs might require you to solder the cells, which is not for the faint of heart.

I've tried rebuilding the battery for an x220 twice and both times the battery case ended up too damaged to be used. I'm about to fork over $100+ for my forth battery for this machine.

I am confused. I have a Thinkpad X220 I bought used. The original battery is still usable for my purposes. (I don't use it for travel so I haven't tried using it for more than a few hours at a time.) I just looked on Ebay and the most expensive batteries listed for the X220 are less than $50, with some less than $20. Am I missing something?

As a rule of thumb, any laptop battery for less than $50 is recycled crap.

There are companies who mix-and-match recycled cells and combine them into Ebay batteries out there. Beyond the explosion risk innate to Li-Ion, you're going to get bad battery life with these recycled cells in the very best case.

The cheapest "legitimate" laptop batteries I've found come in the ~$80 mark.

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A good and proper 18650 cell costs $7.50 alone, and you'll need six of them to build a laptop battery.

https://www.amazon.com/Samsung-INR18650-25R-Rechargeable-Bat...

That's $45 for 6x proper cells straight from the manufacturer. Plus labor, plus all the other parts of the laptop battery (chassis, protection circuit, etc. etc.). Anyone selling for less than $50 is straight up recycled mix-and-match junk. Its the only way you get to $20.

And before you go look up cheaper cells: Ultrafire cells are recycled junk. So ignore all of those listings. Its best to stick with Panasonic / Samsung / other name brands.

Man, I was thinking about taking on this challenge next. I have 2 of the extended batteries that work excellent but the regular battery wont hold a charge for more than a few hours.

So the main issue was not damaging the case? Did you have any references or guides?

The cases aren't meant to be opened. I followed some guides on YouTube. Most require using a saw and really sharp knife.

Can you recommend a good place to get new 18650 cells? I live in Norway.

I’ve been wanting to order some but obviously don’t want to buy them from some rando off of eBay because I don’t trust that they will

1. actually be new, and

2. that even if they are new they won’t explode in my face

I'd use Farnell. They're a huge, reputable, supplier that takes product direct from the manufacturers.

I don't know how easy it is to get them to ship to you, nor how easy it is for individuals to buy from them.

UK: http://uk.farnell.com/search?st=18650

Norway: http://no.farnell.com/search?st=18650

Genuine Panasonic 18650s are decent. Not had any problems so far with ThruNite either.

there is probably a more 'electronics' source available, but these are pretty much the go-to batteries for vaping, so probably any reputable vaping vendor might be a good, if overpriced supply...

Norway? Isn't Nkon next to your door?

Never heard of Nkon. If you mean in the almost literal sense then I think you might be conflating Norway and the Netherlands? But if you just mean that they are next door in terms of being in Europe then yes so it seems. I’ll have a look at them thanks, along with the others people have mentioned.

Yes, I meant that-end-of-EU, sorry for coming off cheeky. Winning the great EU customs roulette with batteries is not worth it if there is an OKish intraEU seller. Plus, a lot of discussions about it's batteries in .ru (!) internets.

Hey, also live in Norway, I've ordered from NKON before, just use https://ru.nkon.nl (we're outside the EU VAT region).