I'm just thinking about a guy in a garage trying to figuring out why something don't work anymore. He pushes a button, waits for the "click" of the relay, but he won't hear anything. Is it broken, or is it an transistor? This might not be the reason, but it's probably a pro for relais. It's way easier to tell if they're broken.

Mhm while you're right, this is not the topic in both of the questions.

@Andyaka amount of Nickel per energy or per weight should not require absolute sizes. But as an example: nickel/100Wh

@IgnacioVazquez-Abrams , Lithium is used as cathode, nickel as anode. Where is the different purpose?

Uhm,... so I'd better go with ordering the suitable coil, due it's meant to be light weight (FPV system on multicopter). But still, I learned something. Thank you!

true. Feel free to edit, my english is surely not the best.

I already edited my post accordingly. From "Never try to extinguish Lithium with water" to "Water is not the ideal extinguisher for lithium"