When Moving The Battery To The Boot...

[Guest Dave]

Im planning on moving the cars battery to the boot to free up some space in the engine bay. Im going to mount it inside a sealed box which will vent through the boot floor, so I think the safety side is covered, now about the wiring.

I was planning on getting some bad-ass heavy guage cable and running it to the original battery terminals on the cars loom and joining it, but, do I have to run both a positive and negative, or could I run just a positive wire, and earth the battery to the chassis in the boot, and earth the old negative connections in the engine bay? Theoretically this would work fine, but in practice, would this create problems with dodgy earths etc?

 

Any other problems I may encounter?

[Guest jonnie205]

yes as long as the engine is earhed to the body then you will be fine just earthing the negative side of the battery to the boot floor or something, that is what all competion cars do. you never need to run the earth down the car as all the eatrh is doing when the battery is under the bonnet is going straight to the body.

[Wurzel 16]

Might be worth sticking a fuse close to the positive terminal in the boot if you're going to run a length of cable along the car.

Either that or make sure the cable is very well protected agains chafing on the chassis.

[Guest kate205gti]

minis (proper ones!) have one positive cable running up the underside of the car and the negative earthed on the body shell in the boot and that seems to work ok.

 

I had a cut off switch in the dash on mine and wired that in with lightening cable and had no probs, as nick says just make sure its secured tight to the underside of the car and doesnt rub or hang down, it will soon get a protective layer of dirt!

[C_W 3 1 Cars]

I got the impression they were talking about laying the cable(s) inside the car (personally I would prefer to see it laid inside the car).

[Guest Dave]

Yeah, it will be going inside the car and I will be using a big fuse at the positive terminal. Im not sure what rating fuse to use, so I suppose its trial and error till I find one that doesnt blow when the starter is cranked, headlights are on etc etc. Having said that, minis dont have fuses in the battery cable. Hmm.

 

 

The reason I asked about the earth wiring is because I dont want to have any problems with dodgy earths.

[Wurzel 16]

It isn't necessary to have a fuse inline with the batter lead, just precuationary.

 

I wouldn't feel to safe knowing that I had a relatively long length of live cable in the car unprotected. I know that Pugs don't flex very much being a small car but they do flex more than minis.

 

Sufficient cable protection can be applied around potential areas of chafing for a fuse not to be warranted. For me though, the real reason would be if I were to be V unlucky and stove the car in causing the cable to arc against the chassis. It would burn a bloody big hole and melt the wire fairly quickly but with all that petrol etc getting chucked around........

 

Be in no doubt though that the fuse required (if you do fit one) will be fairly hefty to accomodate the cranking current. The size of the cable attached to the starter motor (live cable) will give an idication. From what I can remember, 10mm squared cable will handle around 70amps as a rough guide.

Edited November 8, 2003 by Big Nick

[red 0]

I did this years back in an Escort and ran the cable throught a quality piece of hose for extra insulation/and protection and fitted P clips very close together to secure, but if your running it under the carpet it may be a bit harder to do, I also fitted a battery isolation switch next to the center consol.

 

Regards Russ......

[fiji bob 0]

the cable might not actually melt if its thick enough it will just get very hot and could set fire to the carpet if its not fused, id start with a fuse rating of 100amps and go up 50 or so if it blows while cranking

[Wurzel 16]

the cable might not actually melt if its thick enough it will just get very hot and could set fire to the carpet

 

That's alright then, at least the cable wont' melt through.

 

I don't think I'd like to witness exactly what would happen.

[Guest wes]

Use a resetable circuit breaker

[perfecto pug 0]

in electrics you fuse to protect the cable, so find out the rating of the cable and get a fuse to match

 

even if a fuse is rated 50amps it wont blow at 50amps, and some types of fuse will need double the amps to blow in a short space of time.

 

you learn something every day - it helps that i am doing an electricans course at college

[cybernck 402 1 Cars]

yup, earthing it anywhere in the boot is perfectly fine.

 

we run our positive through a cut off switch/fuse.

 

 

[Guest Cookie]

Best to not use stupidly large diameter wire either, or the voltage drop will give poor starting.

 

Ian

Edited November 10, 2003 by Cookie

[Beastie 1]

Best to not use stupidly large diameter wire either, or the voltage drop will give poor starting.

 

Ian

How do you work that one out then?

[Guest dave364634]

use 4awg minimum imo, and imo only.

 

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