There can be multiple reasons why a battery does not last very long, below are a few examples:
Has anything been left on? Make sure when exiting the vehicle that the master switch has been turned off.
Did you use a motor mover to put the van into storage? Using a motor mover uses a lot of power and the battery must be recharged after its use. A battery must never be left in a discharged state as this will over time damage it.
It could just be a faulty or worn out battery that requires replacing; please do not use the green light as an indicator of a fully charged battery as this only indicates the voltage and not the capacity.
If you are still experiencing problems ask a Dealer/Retailer to carry out a drainage check to see if there is an issue.
Yes, but the generator must be started OFF load, this means starting the generator before it is plugged into the Caravan and leaving it for a couple of minutes before connecting it to the vehicle, the reason for this is that it prevents large voltage spikes going into the vehicle and potentially damaging appliances.