What replacement battery do you use? I'm looking for a backup for my X220, but all the aftermarket batteries have terrible reviews and I'm afraid the $90 original Lenovo ones are degraded after 10 years and not worth the money.
The machine still runs Linux like a champ -- I'd just like a new battery so I don't have to have it plugged into the wall at all times.
Most replacement batteries seem like they use fairly "standard" cells, which aren't all that hard to obtain.
To be frank though, I do not expect this battery to last 10 years. I'll be happy if it maintains its 4-hour charge over the next couple years. If you're operating on that kind of timeline you might be out of luck.