Thanks for your reply Stevie, it's the main van battery I only replaced it yesterday thinking it was faulty, and this morning it started but not as it should. Its a DIY conversion I have bought privately.Hi and welcome to the forum!
Where to start?
Do you mean that the vehicle battery is draining or that a separate ‘camper’ battery is draining?
Depending on your battery set up and charging system/s it’s difficult to advise.
Is your camper a professionally built vehicle, or a self build?
Frankly, there are so many possibilities is very difficult to offer a solution. If you don’t feel competent at having a go at locating the problem yourself, I’d suggest having an auto electrician look it over.
Depending where you’re located, there maybe another member here with some knowledge that’ll cast an eye over the problem.
Sorry I can’t offer any constructive help! I’m sure others will have comments to add and good luck with getting it sorted.