Lithium-ion batteries can hold a charge for many months. It is best to store a lithium-ion battery with a partial or full charge. Occasionally, a lithium-ion battery with a very low charge stored for a long period of time (many months) has its voltage slowly drop below the level at which its built in safety mechanism allows it to be charged again. Somechargers can provide the ability to overcome the protection device and allow recharging. But not all can do this. So, iIf the battery is going to be stored for several months it's a good idea to take it out and recharge it after a few months. Better yet would be to actually use the battery every few months and then leave it partially or fully charged. Remember, one good thing about LiION batteries is that they have the lowest self discharge of all the battery types we commonly use.
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