Cable for battery in boot

[Rob]

As per the title, what size cable should I run to put a battery in the boot of my ST185? and also is running an earth back to the engine a good idea?

Cheers for the help
Rob

[steroidcontaskie]

Not sure if there is a rule of thumb or not. But for my soarer I ran 0 guage to the boot and ran the ground to the chassie under the boot. Havent had any problems with that setup, but I guess running it back to the factory earth would be technically better

Cheers
Ed

[loudstealthGT-Four]

^^^ +1

I run a 0 gauge wire to the boot for the positive and then just earthed the battery in the boot, no issues in the last 2ish years

[92mr2paddy]

yea same here works fine, dont wory bout running back to front of car as the whole car acts as 'earth' so anywhere works fine, and the shorter the less wire you have to buy for the earth so thats a win, hah

[holden_fan2005]

Same as above. Talk to ya local auto sparky as they can get decent quality cable generally for a good price. I ran my earth back to the block and also to the boot but I might remove that as others don't seem to be having issues (and I don't have any electronics)

[Rob]

Thanks guys. Now what size is 0 gauge? and I would assume double insulation is best?

[allencr]

...assume double insulation is best?

It's more no chaffing, no pinching, no rubbing- preventing insulation problems rather then only relying on it.

[Grrrrrrr!]

0 gauge is pretty damn beefy. Its about 9mm diameter of stranded copper.
Strangely enough thats about the size of the cable to the starter motor in an MR2.. And I happen to have one that i'm getting ready to send to scrap. Want me to try to pull the cable for you?

[RomanV]

I've done exactly that, used an MR2 cable for a car with engine in the front, battery in the back (opposite if what SW20 is)

It works well, If need be I'd do it that way again.

Saves wondering if it will work or not, big enough wire or not, etc etc when you are using a factory part exactly as intended.

[Stott69]

Keep in mind that a fuse in line will be a good idea if anything does wear through. When I did this to my trueno I used a kill switch to join on to the old positive cable

[RomanV]

Oh yeah. I used part of the SW20 fusebox as well as the cable, mounted to the side of my battery box...

The whole thing goes through a 100amp fuse from memory.

Parts scavenging ftw

[Bling]

viewtopic.php?t=62651

[Grrrrrrr!]

100 amp fuse? Yeah, Nah.. thats not going to handle cranking a 3sgte on a cold morning.

3sgte starter is rated at about 1.5kW which at 10Volts is 150 amps. 200Amp fuse would be minimum i'd even think about using and even then i'd make sure I carried a larger rated spare at all times for the first 6 months or so. Starter motor cable in an MR2 (and AFAIK most other cars) is not fused at all. The alternator Fuse in an MR2 is 120Amp, and thats a piddly little cable (4ga?) compared to the starter motor cable. Just think about how many Cold Cranking amps batteries are rated at.. 400+

[steroidcontaskie]

I also thought that 100 amps wouldn't be enough, so I put a 100 amp breaker on the cable at the engine bay end and a 150 amp fuse just after the battery in the boot. My 2jz starter is meant to be 1.6kw but it doesn't even trip the breaker

. So I wouldn't be surprise if you where ok with 100amp fuse, but I would go for higher with a breaker in the engine bay.

[Grrrrrrr!]

Thermal breakers are SLOW.. you'd need a good 30secs of cranking before you had a chance of popping that. Surprised the fuse hasn't popped in the middle of winter tho.

[steroidcontaskie]

Probably haven't run the car in winter yet, but I did spend a good 60s cracking the engine over on the starter last September. But Grrrrrr is right, go with 200+ amps, no down side to being a bit on the large side, but lots of problems if you are too small (or so I have heard )

[XS1V]

I have a length of 0 gauge cable here on the shore if your interested, normally $25-$30 a meter otherwise

Brad