The batteries weren't even scruffed up so as you can see the contact is really strong with a shorter contact time than 1 second!
Items needed:
- Stranded copper wire
- 18650 cells
- 80w soldering iron
- Flux / acid (I used this German stuff called lötwasser which I think translates to soldering water but it's some kind of acid)
- Leaded solder
![](https://s2.save4k.ru/pic/pptK4TTZr8Q/maxresdefault.jpg)