So I'm just toying around right now with a bunch of 18650 Lithium-ion cells that I've liberated from old laptop batteries. Individually they do not pose a significant electrical risk; they can be fully charged and you can touch both ends with you hand and not feel anything. However I've currently got about 60 (and growing) of them which I'm in the process of testing discharge rates and capacities since most of them are unlabeled. Aside from the obvious danger of overheating and fires with regards to charging and discharging A thought just occurred to me that if I hooked all these fully charged in series I'd get about 240Vdc. Even at a pretty conservative 2A discharge rate that's 480W. At what point do I need to start worrying about personal safety when handling a pack of these cells? Information on AC dangers is pretty easy to find on the net, but I'd be pretty ignorant if I just used that data to make assumptions about DC. I take it there's a bit more involved than my knowledge goes, I mean your average car battery can discharge over 300A at 12V and touching both terminals doesn't kill you despite that being more watts than a household power socket. I assume there's more than a few people doing DIY solar setups these days too, where I imagine safety would be a significant concern.