Bongo Fury

I'm trying to diagnose some charging issues with my leisure battery. My question is what is the expected voltage at the LB terminals when the engine is idling? I have a split charge setup, but I don't think it's voltage sensing... I think it just uses the current from the ignition when running... anyways..

I get the following measurements:
SB - 14.10v
Wire into relay from fuse box - 13.86v
Wire coming out of relay to LB - 13.74v
LB - 13.7
Waeco 12v plug (dedicated wiring from LB) - 13.72

Does this sound about right or am I losing too much voltage to the LB in the wiring somewhere?

I get exactly the same voltage across both batteries on tickover(around 14.2V last time I checked).

There is only a relay and some fuses between the two batteries when connected together via the split charge system so there should be minimal or no voltage drop.