The lead-acid battery must be stored only in a charged state. At temperatures below -20°C, the battery must be charged once a year for 48 hours with a constant voltage of 2.275 V per cell, and at room temperature - once every 8 months for 6-12 hours with a constant voltage of 2.35 V per cell. Storing the battery at temperatures above 30°C is not recommended.
A layer of dirt and scale on the surface of the battery becomes a conductor for current from one contact to another and leads to self-discharge of the battery, after which premature sulfation of the plates begins. This is why the surface of the battery cover must be kept clean (wash before storing). Storing lead-acid batteries in a discharged state leads to a rapid loss of their functionality.
When storing the battery for a long time and discharging it with high currents (in starter mode) or when the capacity decreases, it is necessary to conduct control and training («medicinal») cycles, that is, discharge-charge with currents of nominal value.