OK we've all read stories now about exploding cell phones and fires. Thus we know that lithium-ion batteries can deliver a lot of current in a short interval. Usually there are safety tools in place to prevent this from being an issue.
So I bought a device that not only removes those safety tools, but leverages them for its functionality. Its... a set of battery-powered heated gloves. That's right, these 'warmspace' gloves (you can buy them here!) have a pair of lipo batteries 'very comfortably stuffed' into them. And when you press that little red dot you get 3-levels of heat (42-55C they say).
Now... Do they work? Yes. They heat. Comfy. Even without the heat they are OK gloves.
Are they comfortable? Not bad, a bit bulky, the battery on the top of your rist is a bit 'not great'.
The sum total of documentation (and 'regulatory statement') is this doc below. The product packaging was a plastic bag with a sticker saying "GA800A", so lets go w/ that. I think it means '5W heating' from '7.4V/4000mAH', 2 somethings(?charging time in hours?), 3-5 hours of run-time @ 42-55C. The last column seems to be 'fever area' according to google translate, so i think that means heating zones. And mine has 'four' so I think it means my thumbs are not heated.
The astute amongst you will notice the unusual charger. Its a dual-outlet, which are tied together in parallel. This means you take each battery pack and plug it into the charger at the same time. No problem, right? Well, what if one pack is near discharged and one is near full? Then suddenly a lot of current will flow from the 'full' to the empty battery. Hmm. So yes, parallel lithium packs are a thing, but you must make sure they are near the same voltage when connecting to avoid that inrush.
Fortunately if these catch fire while I'm wearing them, the combination of plastics, polyester, spandex, etc... should melt down nicely onto my skin. Safety first!