pewpew wrote:

Any 18650s not in use to be stored either in fridge @ 5°C or, more practically, in powerbanks.
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.

Storing 18650s in the fridge isn't a great idea. It was fine for older NiCad batteries because allowing them to discharge completely didn't harm them (and occasional complete discharge to zero helped avoid memory lock) but lithium ion cells can be permanently damaged if they are allowed to drop below 2.5 Volts.

All batteries will self discharge faster in cold weather, sticking li-ion batteries in your fridge is asking for trouble. Batteries discharge faster in cold weather and storing them in the fridge is risking them falling to below 2.5V before you have noticed.