I have recently become the owner of a '97 diesel Bongo, it has a full side conversion and looks to be a JAL (as has a JAL speedo). It has a leisure battery and a zig cf9, unsure if it has SCR of if it does what type - there is an anonymous switch above the rear fog light switch.
Sorry for the long post, hope it entertains..
This is my first Van and so far happy with it. I took it out within the first week for one night, ran the fridge a little and the lights of the leisure battery. On return ( around 60 miles) found the leisure battery to be flat. Fitted a new LB and now all seems to run well, as have been away with no issues since.
I use the van for commuting sometimes (depending if i want to cycle or not). Anyway accidentally managed to leave the vehicle lights on the other night ( I climbed over into the back and exited through the side door

On return SB was flat, unsurprisingly, but the LB was also flat. Got a Jump start and drove the long way home (about 10 miles), as it was a new LB wanted to ensure it was kept in good health so put it on EHU for day.
Van started fine in the evening and off to work I went ( the long way again), Started fine the following morning too for the drive home. Picked up a trickle charger for the SB but did not use as in the afternoon went to check both batteries and both had reading of 12.65v.
And this is where the questions begin:
Why did both batteries drain while vehicle lights were on?
Why did both charge whilst on EHU? zig cf9 was on VAN battery.
If I use LB not on EHU will it also drain the SB?
I have trowelled through your wonderful forums and not found the right answers, I did some more multimeter testing but unable to measure Amps.
Don't know if this info will help but here it is anyway -
Vehicle off - SB 12.65v LB12.65v
Vehicle on - SB 14.4v LB 13.5v
Vehicle lights on, engine off - SB 11.98v LB 12.45v
No change to volts with anonymous switch use.
Sorry if this has been answered elsewhere or if its normal business for the bongo, but I would like to be able to use the bongo without EHU sometimes and don't want to drain the SB, also don't want to damage either battery.
Any help would be greatly appreciated,
Thanks
Ben.