Swapping from OEM 2nd battery to dc-dc. What to do with the VSR / relay

[Toffermora]

So some more questions for you lot regarding this. I have just received my leisure battery and it doesn't fit under my seat so am thinking of putting it near the rear wheel arch as the furniture I am getting has a cupboard there designed for a leisure system.
Question 1: I was thinking of cutting off the relay then adding a midi fuse and then running a 16mm cable from there to the back. Is this ok? The OEM cable isn't 16mm so is it thick enough for a run this long and is it ok going from a smaller diameter cable (OEM one) to a larger (16mm) one?

Question 2: I will need to extend the ignition live cable, what diameter cable should I use for this?

Question 3: am I ok using the chassis ground near the rear lights for my main ground?

Thanks for the help!!

 

[n10n]

So some more questions for you lot regarding this. I have just received my leisure battery and it doesn't fit under my seat so am thinking of putting it near the rear wheel arch as the furniture I am getting has a cupboard there designed for a leisure system.
Question 1: I was thinking of cutting off the relay then adding a midi fuse and then running a 16mm cable from there to the back. Is this ok? The OEM cable isn't 16mm so is it thick enough for a run this long and is it ok going from a smaller diameter cable (OEM one) to a larger (16mm) one?

Question 2: I will need to extend the ignition live cable, what diameter cable should I use for this?

Question 3: am I ok using the chassis ground near the rear lights for my main ground?

Thanks for the help!!

#1: depends on dc-dc charger max charging current. OEM cable is 10mm^2 so you should plan and fuse based on that, not 16mm piece of run.

#2: doesn’t really matter. Signal wire to dc-dc charger will not carry almost any current so it can be literally anything. I would use what I had pre-existing or if buying, 0.5-1mm is plenty

#3: yes

Edit: #1 cutting off relay, using midi fuse instead of it and switching to thicker wire is ok. But you can’t increase amperage based on the thicker wire run, it only helps to reduce voltage drop and wire heating on the run from seat base to wheel arch.

 

[Toffermora]

Ok thanks, so do you think it would just be better to run in a new cable from the starter battery to the leisure battery that was fused approximately rather than two different sized cables?

 

[n10n]

Ok thanks, so do you think it would just be better to run in a new cable from the starter battery to the leisure battery that was fused approximately rather than two different sized cables?

Of course a one size cable without joints throughout would be better. But quite a bit more work to fit and also you then lose the connection point below the seat - it would be convenient to fit a small fuse box eg for USBs there.

OEM 10mm^2 is about 7AWG and looking at charts, eg Automotive Wire Amperage Capacity Chart - Jasco Automotive Ltd, should be good for at least 40A, conservatively, on a run from battery to seat base. So I think you would be fine using OEM cable - at least if the charger you’re fitting is 40A or less?