My Proposed Wiring

Richard85

Richard85

Senior Member
VIP Member
T6 Guru
Afternoon All,

I'm going to be installing a Leisure Battery in my van soon - I have ordered what I believe I need - Specs Below:

- Victron Orion 30a DC DC Charger
- Victron Smart Shunt
- Fogstar Drift 105ah LiFePO4
- 100a pos & neg busbars
- 16mm2 Cable
- 60a Midi Fuses
- Yet to order 12v blade fuse distribution & cables - suggestions welcome

Would appreciate feedback on my proposed diagram based on the list of kit above. This is my first attempt doing this so suspect i will have missed something somewhere.

Cheers all,

Richard

Van Leisure Wiring V1.jpg
 
There is a huge amount of info on the forum on 12V installations, I’m guessing that every possible combination & permutation has been covered at some point. There are some basic first principles that need to be considered on any project wrg fusing, cable sizes etc. I’m sure a search would answer most of your questions. @Dellmassive has put the time into writing some excellent “how to” threads.
 
I'm assuming you don't have cabling in place already for the factory fitted 2nd battery.

Also, is this going under one of the seats or elsewhere?

Couple of changes/suggestions:

Fuse the cable from the SB to the DC-DC at both ends, the factory set up uses a 100a at the SB and 80a at the split charge relay, but 60a would be fine there.

DC-DC charger - if you can stretch to it, the new Orion XS 50a is a worthy upgrade over the older 30a. It's much much smaller, runs a lot cooler and can charge up to 50a rather than 30a.

Depending how long your run is from the positive busbar to your 12v fuse box, if it's long (and you won't be using 16mm² as that's overkill) then fuse that as close to the busbar as you can.

Same for the DC-DC charger, fuse the run on the OUT side to the positive busbar with a 60a fuse.

Do you know how many 12v DC circuits and fuses you'll need and what the amp rating is?

As @Salty Spuds says, there is a wealth of information in this forum, many of it posted by @Dellmassive in his 'how I done it' threads so make a coffee or two and waste a few hours/days going through this!

There's also a lot of useful YouTube channels which explain things in easy to understand ways like explorist.life. In fact I was watching one of theirs the other day on fusing and why and where it's done.
 
Salty Spuds said:
There is a huge amount of info on the forum on 12V installations, I’m guessing that every possible combination & permutation has been covered at some point. There are some basic first principles that need to be considered on any project wrg fusing, cable sizes etc. I’m sure a search would answer most of your questions. @Dellmassive has put the time into writing some excellent “how to” threads.
Click to expand...
Cheers, yes I've read a fair bit and taken away what I think i need which is how my design has come about, however there's not a great deal to be found on basic alternator only systems - just after a sense check of my interpretation / design before I install.

The plan will be to add solar at some point but currently not required.
 
TallPaul_S said:
I'm assuming you don't have cabling in place already for the factory fitted 2nd battery.

Also, is this going under one of the seats or elsewhere?

Couple of changes/suggestions:

Fuse the cable from the SB to the DC-DC at both ends, the factory set up uses a 100a at the SB and 80a at the split charge relay, but 60a would be fine there.

DC-DC charger - if you can stretch to it, the new Orion XS 50a is a worthy upgrade over the older 30a. It's much much smaller, runs a lot cooler and can charge up to 50a rather than 30a.

Depending how long your run is from the positive busbar to your 12v fuse box, if it's long (and you won't be using 16mm² as that's overkill) then fuse that as close to the busbar as you can.

Same for the DC-DC charger, fuse the run on the OUT side to the positive busbar with a 60a fuse.

Do you know how many 12v DC circuits and fuses you'll need and what the amp rating is?

As @Salty Spuds says, there is a wealth of information in this forum, many of it posted by @Dellmassive in his 'how I done it' threads so make a coffee or two and waste a few hours/days going through this!

There's also a lot of useful YouTube channels which explain things in easy to understand ways like explorist.life. In fact I was watching one of theirs the other day on fusing and why and where it's done.
Click to expand...
Thanks for the reply. Whats the purpose of fusing both ends of the same run? No problem doing it if required.

I have already ordered the 30A orion - did consider the 50 but couldn't seem to find it in stock anywhere, plus the cost put me off a bit.

No existing / factory cabling - will be installing myself. Battery, charger, shunt and busbars will be under drivers seat. Would like to put the 12 distribution under the passenger seat. Is there any harm in using 16mm to the 12v distribution if I have the cable spare anyway?

I will need 2 x LED spot circuits (4 lights on each), 2 x LED reading lights 3 x usb sockets and 2 x lighter sockets. not done the exact calc but isnt critical yet ( i will before i install).
 
Last edited:
Richard85 said:
Thanks for the reply. Whats the purpose of fusing both ends of the same run?
Click to expand...
Because you potentially (see what I did there?) have a cable supplied from both ends, I.e the B2B & the leisure battery. So if a fault develops on that cable, it will blow the fuse, but the cable will still be supplied by the upstream source. A common misconception is that fuses are to protect the load, in fact the primary duty of a fuse is to protect the outgoing cable. The fuse should be as close as practicable to the source to reduce the amount of unprotected cable.
This has been well covered previously.
 
Richard85 said:
Thanks for the reply. Whats the purpose of fusing both ends of the same run? No problem doing it if required.

I have already ordered the 30A orion - did consider the 50 but couldn't seem to find it in stock anywhere, plus the cost put me off a bit.

No existing / factory cabling - will be installing myself. Battery, charger, shunt and busbars will be under drivers seat. Would like to put the 12 distribution under the passenger seat. Is there any harm in using 16mm to the 12v distribution if I have the cable spare anyway?

I will need 2 x LED spot circuits (4 lights on each), 2 x LED reading lights 3 x usb sockets and 2 x lighter sockets. not done the exact calc but isnt critical yet ( i will before i install).
Click to expand...
It's just due to the long length of cable between the starter battery and under the passenger seat, you're looking at a few metres, and with the DC-DC bring connected to both the SB and LB you've got 2 sources of potential power if that cable is short circuited.

If you did change your mind on the 50a Victron, 12v planet still have 2 in stock at £305...

www.12voltplanet.co.uk

Victron Energy Orion XS 12/12-50A DC-DC Battery Charger

--CALL TO PRE-ORDER-- Next generation 12V DC-DC charging solution from Victron Energy. Smaller, lighter, cooler, more powerful & now with a VE.Direct port to connect to GX devices.
www.12voltplanet.co.uk

Your DC loads are basically nothing, then haha! With everything turned on you might see 20a, I'd guess.

No harm in using the 16mm² but you'll have more trouble getting under the carpet etc to the other seat base than if you used 10mm² or 6mm². 16mm² is good for 110a!
 
TallPaul_S said:
It's just due to the long length of cable between the starter battery and under the passenger seat, you're looking at a few metres, and with the DC-DC bring connected to both the SB and LB you've got 2 sources of potential power if that cable is short circuited.

If you did change your mind on the 50a Victron, 12v planet still have 2 in stock at £305...

www.12voltplanet.co.uk

Victron Energy Orion XS 12/12-50A DC-DC Battery Charger

--CALL TO PRE-ORDER-- Next generation 12V DC-DC charging solution from Victron Energy. Smaller, lighter, cooler, more powerful & now with a VE.Direct port to connect to GX devices.
www.12voltplanet.co.uk

Your DC loads are basically nothing, then haha! With everything turned on you might see 20a, I'd guess.

No harm in using the 16mm² but you'll have more trouble getting under the carpet etc to the other seat base than if you used 10mm² or 6mm². 16mm² is good for 110a!
Click to expand...
Right OK - I understand now cheers, will get another fuse ordered.

I may upgrade to the 50a one day but for now I'll stick with the 30a - what i hoped was going to be a relatively cheap project has already spiraled, I cant make it worse!

Yes my loads are very small however just want the capacity to be there if i decide to expand in the future. All cooking is gas, yeti cooler as a fridge, no TV etc. Just want to be able to have lights and charge devices for a few days when we go away - particularly in winter.

Will sort some small gauge cable for the 12v fuse box supply.

One final question - would you recommend an isolator for this design?

Thanks again - very helpful
 
Richard85 said:
Right OK - I understand now cheers, will get another fuse ordered.

I may upgrade to the 50a one day but for now I'll stick with the 30a - what i hoped was going to be a relatively cheap project has already spiraled, I cant make it worse!

Yes my loads are very small however just want the capacity to be there if i decide to expand in the future. All cooking is gas, yeti cooler as a fridge, no TV etc. Just want to be able to have lights and charge devices for a few days when we go away - particularly in winter.

Will sort some small gauge cable for the 12v fuse box supply.

One final question - would you recommend an isolator for this design?

Thanks again - very helpful
Click to expand...
Get used to costs spiraling! :rofl:

Yeah I was going to suggest an isolator switch, some don't bother and just pull a fuse but it's nice to be able to cut all power in your system quickly.

You'd mount it after the main battery fuse - make sure the main battery fuse is as close to the terminal as possible - you could use a terminal fuse as I'm hoping to be doing

www.12voltplanet.co.uk

Blue Sea Systems 5191 MRBF Terminal Fuse Block 30-300A

Space-saving, ingition-protected MRBF 5191 fuse block for high amperage circuits such as DC main feed, inverter, windlass, bow thruster etc. 58VDC, 300A rated.
www.12voltplanet.co.uk
1000008484.jpg
 
Last edited:
TallPaul_S said:
Get used to costs spiraling! :rofl:

Yeah I was going to suggest an isolator switch, some don't both and just pull a fuse but it's nice to be able to cut all power in your system quickly.

You'd mount it after the main battery fuse - make sure the main battery fuse is as close to the terminal as possible - you could use a terminal fuse as I'm hoping to be doing

www.12voltplanet.co.uk

Blue Sea Systems 5191 MRBF Terminal Fuse Block 30-300A

Space-saving, ingition-protected MRBF 5191 fuse block for high amperage circuits such as DC main feed, inverter, windlass, bow thruster etc. 58VDC, 300A rated.
www.12voltplanet.co.uk
Click to expand...
Looks like an easy solution, saves having to crimp more cables - will order one with some cable and an isolator i think! Hopefully that is all for now!
 
Richard85 said:
Looks like an easy solution, saves having to crimp more cables - will order one with some cable and an isolator i think! Hopefully that is all for now!
Click to expand...
It's an expensive fuse vs the mega fuses. Whatever you buy make sure you get spares and that you include the tools to replace them in your toolkit.
 
paddy26 said:
It's an expensive fuse vs the mega fuses. Whatever you buy make sure you get spares and that you include the tools to replace them in your toolkit.
Click to expand...
Good point, cheers - will be sure to order spare mega / midis. Toolkit already sorted.
 
Salty Spuds said:
Because you potentially (see what I did there?) have a cable supplied from both ends, I.e the B2B & the leisure battery. So if a fault develops on that cable, it will blow the fuse, but the cable will still be supplied by the upstream source. A common misconception is that fuses are to protect the load, in fact the primary duty of a fuse is to protect the outgoing cable. The fuse should be as close as practicable to the source to reduce the amount of unprotected cable.
This has been well covered previously.
Click to expand...
So important but rarely done, don’t expect fire insurance to pay out if the leisure system is not up to standard.
 
Fogstar recommend max charge current as 20-30% of battery capacity. We put a Renogy 40a dc-dc in my mate’s van and dialled it down to 20a to be on the safe side.
 
Last edited:
TallPaul_S said:
No harm in using the 16mm² but you'll have more trouble getting under the carpet etc to the other seat base than if you used 10mm² or 6mm². 16mm² is good for 110a!
Click to expand...
I’ve run 35mm2 in conduit between seat bases under the carpet without issue.
One thing to be aware of when currents are specified for cables is that it comes with caveats and depends upon the installation.
I’d treat such figures as absolute limits and not for operation.
For example 110A running through a 16mm2 cable in free air will give a temperature rise in the cable of the order of 55C above ambient: Whilst it will cope, I wouldn’t do it and prefer to keep my cables nice and cool so always oversize with respect to current carrying capacity.

I use this handy graph to give me a ballpark of expected temperature rises

Temperature Rise by Current | ISRayfast

Rayfast offers high-performance harness component products combined with technical sales advice in the sectors of Aerospace, Defence, Motorsport and Naval Marine sectors, as well as many others.
www.is-rayfast.com www.is-rayfast.com
 
@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:

IMG_6942.jpeg

IMG_6926.jpeg

Good luck.
 
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