Really interesting...thanks for the explanation, makes total sense. I think I’m probably basing figures on more modern cars with better electrics. Good to know that’s in range. So, update... Main battery back in, connected up with new earth wire and wire cleaned chassis earth point. Charges to 13.9v with engine on. Split charge wires tidied and connect up to leisure battery. Leisure battery back in, connected up with new earth wire and wire cleaned chassis earth point. Charges to 13.9v with engine running once split relay has kicked in. On mains charger, both batteries charge up to 14.2v peak. Cable painfully fitted from leisure battery, through grommet in engine alongside FI wiring and run along into hole under r&r bed. Fuse box connected up to wire and new earth cable with wire cleaned chassis earth point. Also gives a reading of 13.9v when engine on and 14.2v on mains charge. It also reads the same voltage as the leisure battery when not charging. So, I’m pretty happy with work so far in that I think this circuit to the fusebox is all neat and tidy and doing what I’d expect, no voltage drop so far. Next job is to start adding things to fusebox and run a separate cable from leisure battery to fridge. However, one little annoyance is that I tried to start the van up just before I came in and it now turns over but won’t start... So, not sure if all the fiddling has dislodged a cable, if the main battery was indeed on its way out and now it’s decided to go, the alternator is going or if it’s something completely different! Don’t you just love VWs!