TL;DR don't fiddle around with batteries if you aren't ABSOLUTELY sure what you are doing

For my arduino project I need to use 18650 Li-Ion batteries. They are pretty awesome but at the same time pretty dangerous if you don't use them the right way. You need protection boards etc. or they can/will go BOOM.

So I am looking around Amazon to find some good quality ones and reading some reviews made me wanna cry.

People were REMOVING protection circuits from the batteries and even removing the foil around the batteries. NEVER EVER FUCKING DO THAT!

I also found out that these are the batteries used in E-Cigarettes and now I really don't wonder anymore why they explode so often. People fuck around with the batteries just so they fit into their vapes, or reduce the resistance of the coil (the thing to heat up the liquid) to an absolute minimum so they can get more watts. A side effect of this is that a lot of current gets drawn from the batteries (>20A or something) which makes them go BOOM if no protection/fuses are used in the circuit.