There are an increasing number of caravan sites that offer Mains hook ups. with this source of power, there is less need for big batteries. With an EHU most caravanners wold get by with surprisingly small battery say 20Ah which will carry the normal peak loads without much of a problem, and of course when the load has reduced the power supply will recharge the battery.
The downside of such small batteries, is they also tend to be restricted on the maximum current they can deliver which may not be enough for a caravan mover, but that does depend on the type of battery being used.