If I am not using my cells for a longer period of time, what is the best way to store them? Fully charged? Half charged? In the refrigerator? Freezer? Oven? Bury them? Under the pillow? Give them each a small throne?
Half charged and cool (No reason to freeze them) and in a dry place.
I store them at about 3.7V
Regards,
Roberta 0:)
Half being the midway point between what voltages?
Go for between 40% and 50% in this table:
It is not very critical, you can also measure the voltage on a new battery of the same type, they are usual delivered with about the correct voltage for storage.
Just remember to measure voltage some time after you have removed the battery from any load or charger.
Correct me if I’m wrong, but I understand that the 50% recommendation is not all that exact number. Emptier litiums stay better for longer time - but being completely drained is really bad thing, so they are recommended to stay somewhere in between (~50%), so they would not get fully discharged by accident (or time).
Oh, and I have a faint memory that keeping them at ~50% in room temperature is better than keeping them 100% charged in the fridge temperatures.
I do believe it is something like this.
Not according to battery university: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
Umm… am I reading that table wrong then? I read from there that after one year:
–40% charged battery stored at 25°C (room temperature) is in 96% usable condition.
–100% charged battery stored at 0°C (~fridge temperature) is in 94% usable condition.
It depends on you room temperature, you dont need much above 25C, before the fridge wins.
Heh, where I live (Finland) our normal room temperature is around ~21°C, and 25°C+ feels uncomfortably hot, so I did not even consider that some might be able to survive in such harsh temperatures 
Anyways, it is true that it’s so close that small changes to any direction might change the outcome.