Even if no consumption device is connected to the battery, “it is drained” electrically after a certain period of time since the electrochemical processes cannot be stopped or avoided, as they are part of any battery technology. This is not a phenomenon that is limited only to lead-acid batteries.
The self-discharge rate increases at higher temperatures. Therefore, batteries should be stored in a place with a low temperature.
Due to this effect of self-discharge, the state of the battery should be checked regularly during its storage period (for example, if you decide not to use your vehicle over a certain period of time) as the battery may require recharging