I did in fact buy a knock-off from ebay battery, but it kept it kept it's charge for hilariously little time. Had to run it of mains power permanently (ran it as a little server for a while).

Don't know your exact timing but I run basically on Dells Latitude laptops for past 2 decades. Since its just for travel and not my primary workhorse, I buy used corporate ones for pittance (cca 300$ for models worth 1500 few years before), and swap battery myself for another original OEM one, they cost less than 100$ from original manufacturer. Its just 2-3 philips screws and 1 cable, anybody can do it. They last just as much as advertised on new ones and don't degrade much even after few years.

Batteries (and ie chargers) are one of the things that's utterly idiotic to shop around on chinese portals. You literally always get what you pay for (or worse) and can't punch above this threshold.

This was mid 2010s and the laptop has long since bit the dust. IIRC this was a Dell Studio 15, but I recall checking eBay for old new stock with no luck, but it doesn't surprise me that the Dell Latitudes have lots of stock floating around ebay.

If Sir is buying his lithium batteries and/or power transformers from the likes of eBay, Alibaba and Amazon, then Sir may wish to check his fire insurance is up to date.

I have bought many third party rechargable batteries from those sites over the years. Yes, slightly lower charge capacity compared to original, but no fires. And, yes, I know my sample size is small!

One ebay sourced Chinese transformer that blew its back off (!) letting our the magic smoke and tripping the RCB was enough for me.

These days I'm older and wiser.

I also had similar good experiences buying batteries on Aliexpress. The issue with those typically isn't intrinsic quality as the batteries are most of the time good but lack of quality control. Bad batteries will reach the market and this is specially dangerous with packs with many cells like e-bikes packs.