VSR cable size?

[Phantom]

I think I have found the cause of my leisure battery charging issue - the wire from the VSR to the leisure batteries looks real skinny for the 7m run and is the same size as the VSR little black earth wire. Before starting the engine the battery voltages were 12.7v Starter and 12.2v Leisure. With the engine ticking over the alternator was putting out 10A or so, there was no voltage drop at all through the VSR, 14.04v at the starter battery and at both VSR terminals. But there was only 13.12v at the leisure batteries, so a 0.92v voltage drop or 6.55% which seems a little high. They do charge but maybe not as well as they might with a larger wire size to supply a higher voltage and current like perhaps at least 6mm sq? It's an easy enough job to route it so think I will likely do this before any other options. Maybe an even larger cable would future proof it?

 

[wildebus]

For a 140M VSR on a 7M run, I would probably use 25mm2 cable as a minimum (on my LT camper, I swapped out the 16mm cable that was already in place and installed 35mm2 instead as it was a longish run (of around 5M).
At a minimum, use 16mm2 cable and remember to use fuses below the cable rating (around 80A each end would be about right)

 

[Phantom]

At a minimum, use 16mm2 cable and remember to use fuses below the cable rating (around 80A each end would be about right)

Many thanks for your advice, it is most appreciated.
I understand that the Sprinter T1N alternator is capable of maybe 200A output so possibly a B2B with different batteries somewhere down the line? Is 25mm2 with 100A fuses good for that?

 

[Debs]

Hi, I am not a fan of split charge relays, and switched to B to B, years ago. Your idea of switching to this system with 25mmsq is definitely the way to go, although it will be costly. Just as an aside, all those connectors on the battery look pretty ropey, and a good service of those components will be beneficial. Now we are in lockdown, a good time to do stuff even if the weather is crap.🛠

 

[Phantom]

I decided to go the B2B route instead of VSR as it will be more beneficial for me, but still needed to upgrade the cable size to 16mm2.

 

[wildebus]

Hi, I am not a fan of split charge relays, and switched to B to B, years ago. Your idea of switching to this system with 25mmsq is definitely the way to go, although it will be costly. Just as an aside, all those connectors on the battery look pretty ropey, and a good service of those components will be beneficial. Now we are in lockdown, a good time to do stuff even if the weather is crap.🛠

I really don't like seeing that kind of mess on the Positive terminals, but which you see so often
I got the same kind of thing on my VW LT, which is basically the same wiring setup as the Sprinter T1N, except Phantoms is a little tidier.

LT-Battery-12V by David, on Flickr

The Sprinters in the US use a distribution setup (called a PDC) with fuses on the starter battery in a similar kind of way to the Sevel vans which is much neater.
This is my Ducato ... WAY nicer

I added my own PDC-style distribution fusebox to my own LT to tidy it up and sort out the messy VW/Mercedes cluster

PDC - Exposed by David, on Flickr

 

[Debs]

I decided to go the B2B route instead of VSR as it will be more beneficial for me, but still needed to upgrade the cable size to 16mm2.

I've used 16mmsq, but my cable runs are very short ( less than a metre ) and I invested in a hydraulic crimper, what a difference it makes!

 

[Nabsim]

Hi, I am not a fan of split charge relays, and switched to B to B, years ago. Your idea of switching to this system with 25mmsq is definitely the way to go, although it will be costly. Just as an aside, all those connectors on the battery look pretty ropey, and a good service of those components will be beneficial. Now we are in lockdown, a good time to do stuff even if the weather is crap.🛠

Phantoms starter battery wiring is a lot tidier than mine Debs, remind me not to let you look under the bonnet lol