pewpew wrote:

You can grab cheap Chinese "DIY" powerbanks which are essentially powerbanks with removable cells, sold'n'shipped w/o cells and otherwise assembly hassle free and ready to use.

How long you test it, dangerous situations ?
I am not an electric specialist, but perhaps it is less dangerous.
It seems, we will not have between a 3.2V and a 4.1V battery a 1A current.