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I have spent the past couple of days learning about split charging systems, but there are still a couple of blanks I would appreciate some help on.

1) Am I correct in assuming that you wire all your accessories (interior lights, TV, fridge etc) directly to the second battery via a fuse box and switching system?
2) For items such as the stereo that are part of the van’s main wiring, are there any side effect in having the ignition part on for extended periods of time?
3) I am looking at placing the battery under the drivers seat – does this cause any safety issues and what type of battery is the best?

I apologise if these are answered elsewhere, I have been searching for a while and found a lot of contradicting information. Thanks for your help.
 

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Hi Ben,
I'm doing the same thing at the mo.
I intend to fit a 6 fuse blade holder and wire the different things individually to this with in line switches as needed.
As for stereo, sorry I don't know.
I'm putting my battery under the drivers seat also, there are a few wires/terminals under there to be aware of and also a very handy vehicle earthing nut under the rubber matting.
I've mounted my relay on to the black piece of metal behind the battery (if you undo this metal plate there is a vehicle earthing nut on the bulkhead behind) and run the cable around the top of the engine bay to another detachable black cover,on the drivers bulkhead, I removed this, poked a hole through the black round grommet that you'll see and pushed the wire through, the grommet is in the upper drivers footwell.
Print this off and it'll make sense when you look under the bonnet.
Hope it goes well,
Tony :)
 

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To answer your question - you wire any accessories (lights, TV etc direct to the leisure battery (2nd battery). However, I also have a question mark over fridge wiring - I have been told to wire this as a parallel circuit to the split charging circuit, but I cannot see a reason for this.

Battery under the drivers seat is in theory a good idea, however please be aware that there are safety implications of this.
If you overcharge the battery it then gives off sulphuric acid gas - this is normally vented to outside via a small tube for in cabin mounted batteries. This gas is very corrosive (any electrical modules/wiring in the vicinity will soon suffer). Extreme abuse of the battery (shorting the terminals with a big spanner for a minute or so) could cause the battery to explode - just hope you're not in there at the time!.
Also, if you had a crash where the van ends up upside down, any acid from that battery would end up giving you a nice skin peel.
Having said this, if properly protected, there is no reason why the battery can't go under the seat.

For the stereo wiring - the radio should work with the key in but turned off, or with the key in pos 1 (accessory) - it should be the only load on the battery in this state and there would be no downside. If your stereo only works with the key in pos 2 (ignition on - dash warning light on), then this will quickly drain the vehicle battery, as all ignition fed components will also be working (heaters, electronic modules, engine bay pumps/valves etc). Expect the battery to last no more than 6 hours in this mode (and then you cant start the engine!).
You could wire the stereo so it works from the leisure battery.
 

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nearly a silly answer - use the biggest battery that will fit. Minimum of 85Amp/hour, ideally 110Amp/hour. The bigger the capacity the longer it will last before it needs a recharge, or the more loads you can put on it before it goes flat. But, you have a physical size constraint (and possibly a wallet constraint), so, like everything in engineering world goes, you need to make a compromise: cost vs capacity vs size.

Oh, and gel batteries are recommended for in cabin installations (as they don't leak) - if you want to have safety high on your list, worth spending a bit more money on
 
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