Thank you for that information David.
I did take the batteries off one at a time and recondition them in the garage. I checked the voyages on the batteries once I had conditioned/charged them and they were about 13.6v I then left them over night and they had dropped to 13v.
So yes they could have had it and I now need to replace them.
One other thing is I thought that the charge should also keep the Vehicle battery charged whilst on mains but this is not the case with my van. I have fitted/replaced with a brand new one and after about 3 weeks the battery is totally flat. The only current draw is the alarm/immobiliser.