Please can anyone tell me if I need to have a battery connected on my caravan if I intend to use an electric hook up to the house. Seems an unnecessary expense as long as I am not damaging the system by not having one.
As far as I am aware you don't HAVE to have a battery in the circuit. However, potentially it can cause some problems to delicate electronics as the battery (even if it's not fully charged) regulates or smooths out the possible DC voltage spikes and fluctuations when in use and switching on & off.
It is important that you keep loose the battery terminals insulated or just where there is no chance of them touching each other because the on-board charger will be trying to charge the missing battery.
Dave.
------------- Give a man a fish and he will eat for a day,
Teach a man to fish and you can get rid of him for a whole weekend.
If you want to play safe, just get a car battery and connect it up. Doesn't have to be anything special, but it will do to stabilise the 12 volt supply like Pickled Onion says.