I have a Benimar motorhome which is kept inside a storage facility unattended in the winter . I am disabled so it will not be used during the cold months. It has been suggested I use the EHU to keep the batteries topped up using a timer on the cable for power to run for two hours each day. I am unsure whether I just plug in the cable only or do I have to switch on any of the switches on the power control panel inside the motorhome and leave them on? Advice would be appreciated.
I am not over familiar with "Benimar motorhomes" so I googled images of them. Based on what I saw I'd guess you will have two batteries: One which starts the engine, and runs the driving side of things, and a second battery for the habitation side of the motor home. These two batteries are not usually directly connected together, so you can't run the starter battery down when your using the accommodation, and you cant use the habitation battery to start the engine. But there will be some control system that allows the engine's alternator to recharge both batteries when the engine is running.
The EHU connection will usually power a charger but it only charges the habitation battery.
Which battery or batteries are you concerned about?