My Proposed Wiring

[roadtripper]

I don’t agree that you need a fuse on both ends of the SB to DC-DC cable, only the SB end. There is no output from the DC-DC to SB. Victron instructions show the setup, cable requirements and fuse sizes.

This isn't true for all DC-DC though, there are designs that can reverse charge.

Personally I'd still recommend doing it to account for future changes and maintenance. It's a lot easier to remove/replace the fuse in the electrics area than do the same in the engine bay most times - especially if using the "official" feed from under the battery in the T6 or the high capacity plate fuse box in the T6.1

Fuses are also a point of isolation for maintenance/emergency as well as for cable safety. Consider where you mount the main leisure battery fuse and the supply from the van fuse with this in mind.

 

[TallPaul_S]

@Richard85 I’ve just done similar with the same battery and DC-DC but with a few extra bit. Things to note:

The battery will need to go on its side under the seat.

It is very tight to get the DC-DC in there too and also give it room for ventilation. Do you have a seat swivel? If so that may make it worse. I’ve fitted a fan to mine to keep it a little cooler.

You don’t need Mega fuses - Midi will do just fine and are much, much smaller.

16mm is fine. It fits through the grommet from the engine bay and easily fits under the carpet. Get the extra flexible version (12voltplanet or Simply Split Charge both do it) to make it a bit easier to route. It’s fine for the fuse box too saving buying yet more cable (crimps etc).

Blue Sea make excellent 12v fuse boxes, much better than nameless versions off eBay etc.

Consider a switch on the Orion green plug so you can turn off the DC-DC rather than having it charge every time you start the van.

An isolator is a good idea but takes up more room. Go for Victron or Blue Sea not cheap ones.

I don’t agree that you need a fuse on both ends of the SB to DC-DC cable, only the SB end. There is no output from the DC-DC to SB. Victron instructions show the setup, cable requirements and fuse sizes.

Consider fitting an Ablemail AMT12-2 (tiny and fits next to DC-DC) which will trickle charge the SB from the LB. Very useful and prevents you accidentally running the SB flat while camping if the interior lights keep coming on, locking, lights left on etc.

Consider a fused positive busbar (Like this) so you can protect all cables running from it. Gives simple upgrade path if you want to add solar etc.

There is a ground stud under the seat so you can connect to that really easily. Could save needing a neg busbar as you only have a couple of cables attaching to it.

Couple of pics to show how tight it is and cable channels between seat bases:

View attachment 245776

View attachment 245777

Good luck.

Jesus that 30a Victron is massive!

 

[Dellmassive]

Jesus that 30a Victron is massive!

they run red hot too when pushing 30A . . . . . . i ended up selling mine due to that.

but the 50A Orion XS is a massive improvement, and much smaller too ( as you know)

for anyone reading this and wondering about the "How i done it" references - Dellmassive’s "How I Done It" blogs.

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[TallPaul_S]

they run red hot too when pushing 30A . . . . . . i ended up selling mine due to that.

but the 50A Orion XS is a massive improvement, and much smaller too ( as you know)

for anyone reading this and wondering about the "How i done it" references - Dellmassive’s "How I Done It" blogs.

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Yeah that's another advantage with the Orion XS, yeah it can do 50a but you can turn it down to 30a and it'll run barely hotter than room temperature!

 

[Richard85]

You have all convinced me, particularly after seeing the pictures! - sending back the 30a and going to order the XS. Managed to get it for £270 after 10% eBay discount through work and £15 worth of nectar points! I'll dial it back to 30a as suggested to not risk putting too much into the battery at any one time.

Thanks again for the help all - appreciate there's an abundance of information out there to be found but its good to have designs sense checked after processing what you have read into something you think you need.