make sure you put a fuse in the cable as close to the van battery as possible to avoid any mishaps!
Hi Dave
Interesting thread.
I'm still trying to get my head around this.
My deduction to is this; with the batteries being linked together, both the van and second battery will be supplying your power needs. This is the same principle as lorry batteries; two 12 volt batteries linked together to give a 24 volt output. We were always taught that both batteries had to be the same/similar size as the smaller battery would always do more work and tend to fail first.
Hence if I was to drain my battery today by 20% then being linked together would theoretically (if both batteries were the same) use 10% from each battery.
What size cable would you recommend to link the two batteries together and what size fuse do you use? Also, would distance from the van battery to the second battery complicate matters? I would say that most of us have our second batteries in the back of the van.
I also think that a good starter battery, leaning toward the spec of a traction battery, is more expensive than a good quality leisure battery. I don't know how much Oak Road Motor Factors charges for a 110 amp Banner battery, bit it would probably be more than the £80 I paid for my Numax 110 amph unit 3 years ago.