So, the previous owner explained that it had a leisure battery, which he disconnected when standing 'to save it'. I noticed that all the things he said were fed from the leisure battery still worked when disconnected. When I quizzed him he said it would because the leisure battery would help to start the van. This since rang alarm bells.
What I found under the bonnet was that I have two batteries with an Altec voltage sensing charge relay between them, and a small fuseboard beside the relay which patches into the original cabin fuseboard to cover lights, sockets, radio and blinds. The charge relay wiring was incorrect with a red cable connected to the -ve terminal of the leisure battery instead of +ve. In fact, on further inspection the +ve sensing fuse was removed so the voltage sensing charge relay is doing diddly squat.
More notable was the 'fat' red cable to the +ve terminal of the leisure battery, which I now know is a parallel circuit for the Cold Start option (I also have the engine switch, which confirms it). This is why he said the leisure battery helped start the car and why there's no separation of circuits between batteries despite the second fuseboard and patching.
I read in the forum, the Cold Start option has potential for problems, which I'll touch on later, but it appears to me to be a hindrance.
I read that leisure batteries are deep discharging and shouldn't be used to start a car. I also read that these kinds of batteries don't like being charged all the time by the alternator and can dry out. I then read that the parallel circuit means if the leisure battery is low, it will draw from the starter battery and flatten it. All this sounds really undesirable.
It seems to me that I need one or the other - parallel Cold Start OR voltage sensing charge relay - and I really feel like I need the latter. What do others do in this instance? Can someone give me guidance on where to go from here?
My thoughts:
1. Retain the parallel charge circuit but fit an isolator so I can decide when the leisure battery is connected and gets charged. I would forgo the circuit patching, but would I need to change back to a starter battery?
2. Remove the parallel charge cable and rewire the voltage sensing charge relay circuit correctly splitting out the circuits too. I think this is my preferred option, but how would I terminate the parallel cable to make it safe or where would I need to disconnect it from altogether (the alternator)?
3. If I remove the parallel cable, how does that affect the exhaust valve 'engine' switch, would I need to remove that too?
4. With the problems/considerations associated with the Cold Start option what do I need to keep an eye out for? Is there anything I need to remove/replace?
Thank you