Nice bit of kit!
My problem was that in September I fitted dual batteries and towards the end of the install it started getting dark.
I finished off the big stuff and just had to wire in the trigger supply for the relay.
As it was now properly dark, I cheated and wired this to the +ve (I needed both batteries for the following day)
I then forgot and left the split charge relay wired up like this until....yesterday
Anyway, it looks like lots of short journeys, combined with the drain from the relay and the immobiliser combined, was enough to (over a period of time) flatten the batteries.
It's all wired up as it should be now so I'll have to see how it goes.
Checking it over with a multimeter, it all looks good