A battery not in use is self discharged.
The speed of this process is very variable and however, it’s related to the type of battery and temperature.
The batteries at room temperature completely disconnected with normal ambient humidity, they heat by about 1-1,2 % the group. Increasing the temperature the discharge effect increases: for example, passing from 24 C to 35 C... the discharge car current doubles.
In the cold, the phenomenon decreases until it almost disappears close to the freezing temperatures of the electrolyte. In practice, a battery must be recharged every 20/40 days to prevent its residual capacity to fall
below 60/70%, and that the permanence in this condition causes a beginning of sulfation.
The batteries go stored in dry rooms and possibly not subject to high temperature changes. In these conditions the batteries, can be stored without problems even for about six months.
If the battery is installed on a stationary vehicle for long periods, it is always better to disassemble it,
load and store in a cool, dry place and never in contact with the floor.
Alternatively if the battery remains installed on the vehicle remove the negative terminal and periodically check the o state of charge, any vehicle off absorbs energy from the battery by discharging it much faster of the normal process of self-discharge.