A heads-up to anyone running old laptops; buy genuine replacement batteries while they’re available!
I have an aging XPS 13 and of course, Dell have discontinued the battery line. Opened it up one day and every cell had puffed out. It took buying a couple of fakes before finally finding a decent reseller on eBay who stocked what I needed. The fake batteries were not recognised by Dell’s hardware detection system thing, I imagine lots of other manufacturers might implement the same feature.