Loads of ways to overcharge Neil, typically a
battery and charger miss match, something that Shouldn't apply to Kev BUT a damaged
battery or a faulty charger would do the trick too.
If I couldn't tell if they were
lifepo4 then I'd be putting them in a pouch designed for charging as you mentioned. Leaving them charging overnight while I was sleeping upstairs is not worth the risk no matter how small. Just my opinion of course and I may be going OTT