Starter Battery
A battery type designed to deliver a very high current for a few seconds in order to turn the engine over. A large surface area is obtained with thin and numerous plates; in return its resistance to deep discharge is low and it is not suitable for supplying RV living area loads.
In a starter battery the decisive criterion is not the amp-hour capacity but the cold cranking current. Only a small part of its capacity is used: once the engine is running the alternator refills the battery immediately, and throughout its life the battery mostly hovers around full charge.
If you discharge this battery deeply again and again, the active material on the thin plates sheds and capacity falls quickly. In the field the best-known consequence is this: a user who supplies living area loads from the starter battery for a few nights soon both flattens the battery and cannot start the vehicle in the morning.
The correct arrangement in an RV is to separate the starter and leisure batteries physically and to put a split-charge relay or a DC-DC charger between them. That way the alternator charges both, but the living area load cannot touch the starter battery. Connecting a motorised load such as a levelling system directly to the starter battery is not recommended, because it carries the risk of immobilising the vehicle.
The context in which this term is used: RV automatic levelling guide