Leisure battery

If you are going to charge your leisure battery from the engine alternator/battery, the leisure battery is best places as close to the engine battery as possible. This is because energy is lost when travelling over distance, so you want the batteries to be as close as possible.

Some vehicles have an extra battery tray in the engine bay on which to place the battery. Failing that maybe inside the vehicle. I put mine under the drivers seat, but it needs to be well secured and ventilated.

If you are not recharging the leisure battery from the engine battery you can put the battery wherever you like, ideally close to the solar panel or whatever else device you are using to charge it.

I'm just fitting mine and I have the battery at the back of the van where I intend to put a hob and sink unit, I also have a on/off switch in the cab between the drivers seat and the passengers so I can isolate from the drviers seat.

I've just fitted a relay between the van battery and the leisure battery for charging.

i have my 85AHr battery fitted just behind a sliding door.
there is a vent already in to bodywork there that the vent tube is routed to.
i diy split charge relay feeds the battery via the cable running under the door step cover.

found a great lcd meter on ebay for this too, search d69-30

I guess it depends on your build as to where it will fit. I've seen them placed right at the back in the bottom of a cupboard, doubled up behind the drivers seat in a full width box and i ended up with mine just behind the passenger seats as this was the shortest distance i could get from the main battery (that and my build has a large box running right along that side with some slack space that the battery fits in just nicely, also ment it was easy to put the zig controller in an easily reachable place to turn the lights on :D )

battery is in the bottom right of the pic

I have put my leisure battery behind the drivers seat. It needs to breathe and should not really be placed in enclosed spaces.I also like to make a visual check of the battery, its leads and terminals periodically.