PSA: don't buy your laptop batteries from iFixit! I thought the brand name would mean quality, especially since they included a handy fix kit as part of a package, but the actual battery was not of the advertised capacity and likely had a faulty cell (it jumped from 20% to 0% when discharging, which isn't any good).
ended up buying an OEM replacement part from duracell direct and it works perfectly, so there's really no reason to fall for their substandard aftermarket parts
I got them to send a replacement and it was the same crappy quality (...even down to the serial number reported through SMBus being the exact same as the previous crappy battery, lol), so it wasn't just a one-off...
@eta Hm, this reminds me of an issue I had with a third-party battery seller in NL, 123accu. Got a third-party battery from them that had the exact same problem, let them know, they shipped me a new one... of a different type! Still compatible and same specs, but clearly from a different supplier. That one had no issues at all.
Starting to wonder if there's just one third-party battery supplier somewhere leaving out cells in their packs to cut costs (which was our hypothesis about what happened), and those have now wormed their way into the stock of various sellers...
@eta Wow, that's incredibly expensive too - a similar third-party battery (same specs and type number) is available for like 60 EUR here
@joepie91 in this case, both batteries were identical (same juiced numbers in the SMBus capacity before calibration, same serial number, same crappy aftermarket printing on the battery itself), and the aftermarket printing matched the website listing. I looked past the warning signs in this case because I thought you'd be able to trust the brand name, but I think they're just selling on poor-quality crap!