Self-discharge is a common phenomenon in the batteries, and is closely-related with the storage time as well as the storage condition (especially the temperature) of the battery. Usually, the longer the storage time and /or the higher the temperature is, the self-discharge of the battery is more noteworthy. Moreover, high temperature and high humidity would cause rust of the battery terminals, thus aggravate the self-discharge.

So, proper storage condition for the batteries should be:
(1) clean, cool and ventilated;
(2) with a temperature between 10℃ and 30℃ (no higher than 40℃ in the ordinary course of events) and a relative humidity no higher than 65%;
(3) the storage time should not be too long; the batteries should be well-arranged, and do avoid sort-circuit caused by the contact of the positive and negative electrodes.