moving diesel starter battery under bed help with cablesize

[lloydy]

Hi all, i'm thinking of moving the starter battery on my diesel van (TDI) from the engine bay to under the rear bed. Would 40mm2 cable be good enough?

[bigherb]

Yes as long as you keep the cable length similar otherwise you will have to uprate it.

[syncroandy]

Std. cable is 35mm so yes 40mm should be fine so long as its not too much longer.

[lloydy]

Hmm, thanks for that, i reckon the lengths will be longer, so might be best to go to the next size up if i do move the battery. will have to have a measure.

[syncroandy]

On a petrol its 70mm, do some rough and ready maths to work out a CSA for the new location based on relative cable lengths ?

[lloydy]

Thanks Andy, i've just measured out the cable lengths now...
new location under seat..
Battery to starter positive cable; this will be same length, possibly a bit shorter
Sterling charger cable will be shorter
Battery negative to engine block will be longer so can increase this to 60mm2
Battery positive to alternator will be longer, so i could reuse a redundant 35mm2 cable
I also have another positive cable attached to the battery which i think runs to the old westy split charger which is now no longer used. So should be quite a easy/cheap thing to do. Will then have space for the jx air filter

[bigherb]

Just connect the earth to the body next to the battery and use the original engine earth strap to the body. Connect the alternator cable to the starter so the power then runs up the starter cable to the battery.
Is there a particular reason you want the battery in the van? Seems a lot of work when it works quite well where it is.

[lloydy]

Thanks Herb, that makes a lot of sense
The reason for looking at doing this is (short version)
i have a TDI, the charge cooler is where the air filter used to be. The diesel snorkel now runs up the opposite D pillar connected to a K&N Apollo air filter tucked behind the rear light. the K&N is the only filter that would fit in the limited space, but these do not have the best rep with MAF's and the amount of debris they still let through. So the only way i can fit a normal filter box is to move the battery, it is still a very tight squeeze. A lot of the tdi convertors move the battery to make space.
Just looking at my options really

[bigherb]

Got you now. Rather than taking up living space you could mount the battery where the petrol one is under the drivers seat, the diesel battery is the same size as the 100 battery that fits in there. Cable capacity is not just the cross sectional area it is also the number of strands in that cross section, the more thinner strands the more amps the cable can carry, so you can use the same cross section as the petrol engine but with more strands for the diesel engine. Look at the CCA rating of the battery and find a cable to match or above that, usually welding cables are the ones with thinner strands.

[lloydy]

I have a leisure battery in the space behind both front seats, so thats a no go for me. To be honest the space the battery will go in is filled by a oversized toolbox and spares at the moment, all that stuff is is being put in more space efficient boxes and put in the dead space under the westy wardrobe. So i'm not really losing much, might even gain a bit...

[Plasticman]

out of interest can the heavy multi strand welding earth cables be used , im thinking the the niice big stick welder stuff.
mm

[lloydy]

Yes, it can. I'm using welding cable for all the sterling charger cable (35mm2)
Thats if we are thinking of the same stuff, a few pics buried in my small build thread..

[Plasticman]

yes it will be about as thick as you finger

[lloydy]

sounds about right, got many metres of the stuff in my van