I had someone staying with me recently (last winter to be precise) - skip to TLDR at the bottom as the write up is long...

They were using an older macbook with a battery that didn't last long and didn't have money for a new laptop, so I bought a replacement Kingsener battery and replaced it for them.
Nothing difficult, some screws, a bit of unplugging bits and pieces, something I've done a few times before, although I am not an expert by any stretch,

Fast forward a few weeks or maybe a month the Macbook started crashing and so I thought I must've messed something up.

I had an older Zenbook (bought from GZ) that still worked and was still much newer than their macbook (never had any issues) and I provided this to my housemate.

Another few weeks or so and they reported it had also started crashing and wouldn't turn on.

I can't remember the discussions, but it turned out they were using two heaters in their small room at max temp.

I developed a theory that the batteries died because of the overheating in their hot room.

When removed the battery, the Zenbook would run fine, but with the battery installed it would not boot.

Is there something else other than the battery that could've died? I haven't trouble shooted the macbook, but this weekend will install the original battery which I kept to test if it still boots.

TLDR: Two laptops died after being used in a very hot room with several heaters running - did this hot room possibly kill the laptop batteries or some other part?