Bongo Fury

Main battery to split-charge relay to secondary battery.

All other wiring and fuses left intact.

Will the internal lights and cigarette sockets continue to run when the engine is off?
Will they just run off the secondary battery?
Will the main battery be left alone?

Someone is trying to convince me that fuses 1 and 8 don't need to be re-routed to the secondary battery.
I think they do from what everyone has said.

Will the internal lights and cigarette sockets continue to run when the engine is off? - Yes
Will they just run off the secondary battery? - Yes
Will the main battery be left alone? - Yes
You must connect fuses 1 & 8 to the leisure battery for the above answers to apply - otherwise you will drain your starter battery.

so the secondary battery which comes with the van is purely wired to help start the engine in the extreme cold.
If this is to convert and be called a 'leisure battery' then fuses 1 and 8 need to come off it.

Correct - mine has two batteries and they are linked in parallel to give extra starting power.
Put the relay between them and connect fuses 1 & 8 to the nearside battery, which will become the leisure battery.

You tried harder!!! Thankyou, question answered.

Will go tell someone that they're wrong!

Phew - that's a relief - wouldn't want to be a slacker!!
Let us know how you get on.

Maglett, don't touch anything until someone writes a factsheet. Then, all will be clear.

To answer your questions:-
A secondary battery is there to help the engine start in the cold, YES.

A leisure battery is a slightly different sort of battery, similar size, still 12 volts but it is better at running lights, radios etc. than starting the engine.
Once you (or someone else has) installed the Leisure battery, with the relay and fuse as prevoiusly mentioned in other posts, you will want to give it something to do so in a Bongo the feed to fuses 1 and 8 can be replaced with a new feed from your new leisure battery. This will then feed the internal lights and cigarette with power.
Please forgive me for seeming to be patronising in the explanation but it is vital you know exactly what you are doing with vehicle electrics, there is always the possibility of sparks flying while doing the job and also potentially a fire risk if the job isn't done right.
Someone will write a fact sheet soon or you can google a diagram which will explain where those wires go to from the relay. The relays should come with instructions anyway.
Stay safe.
Tim

Timhum - don't worry, not going to do it myself!
I had a leisure battery which was going to replace the secondary battery (taken from kitchen which I removed last week).
Unfortunately this was tested and came up as 'unservicable'! So it's in battery heaven. The auto-electrician said to use the secondary battery as a leisure one. I'm aware that the cells are different, and a leisure is better suited. Kinda hoping it'll do for now with lights and cigarette sockets.