The battery cover has a ventilation hole through which the battery can "breathe". To prevent the battery acid from being drunk out, it should not be tilted more than 45°.
Conventional chargers and fast chargers can be used to charge the battery. In this case, the battery must be removed for charging.
If an electronic charger is used for charging, the battery can remain installed in the vehicle and not be disconnected from the vehicle's electrical system. The charger's electronics smooth out excessive voltage peaks during charging.
A deeply discharged battery should only be charged using an electronic charger. When charging with a normal charger or a fast charger, the initial current is very high, which causes damage or destruction of the battery.
If the electrolyte level is too low, for example after a long stay in a region with a hot climate, top up the level with distilled water, see section "Maintenance work".
If the vehicle is not in use, the battery must be recharged every 8 weeks.
If the car is not used for more than 6 weeks, the battery is removed and stored in a charged state. The most favorable storage temperature is from 0 to 27°C. At this temperature, the battery has the most favorable self-discharge rate. No later than after 3 months, the battery should be recharged, otherwise it will become unusable.
Clean the battery regularly.
Jump starting devices should only be used in exceptional cases, as they expose the battery to very high currents for a short time.
Caution: Do not turn on the auxiliary starting device without simultaneously turning on the starter.
[The original entry can be found on the portal BMWman]