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Old 07-09-2010, 02:01 PM   #1
berdugo
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Question Thinking of putting the battery at the trunk, what wire gauge to use?

I'm thinking of putting my battery at the trunk area so I can put something on it's place, what wire size do you suggest?

Are 2 AWG 10 in parallel good enough for the +12V of the battery? thanks in advance
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Old 07-09-2010, 04:00 PM   #2
morrocco88
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I went to a welding supply strore and bought welding cable in single 0 size. It was pretty expensive, but I chose to run the ground all the way up to the engine block to avoid having ground issues, so this doubled the amount I needed. I think it was $160 for the cable, but the stuff is big, fine strand copper, really flexible which makes routing so much easier, and it has a thick rubber exterior. It's made to carry large amounts of juice for welding, so it has very low resistance with battery voltage.

I did a bunch of OHMS test on all my chassis grounds and it is very low. Like I said I ran the ground all the way to the block and then the old battery cable ground from the block to the chassis. Put an Optima Red Top in a battery box bolted down in the trunk, and everything works awesome. I figure if your going to do it, spend a little extra and do it right the first time. The last thing you want is ground problems on a turbo motor with lots of electronics.

Good Luck!
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Old 07-09-2010, 09:50 PM   #3
MainFrame
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It's the amps you have to worry about, not the volts. You can run 12V through telephone wire as long as you're not drawing a lot of amps.
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Old 07-10-2010, 12:54 AM   #4
Concillian
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Quote:
Originally Posted by berdugo View Post
Are 2 AWG 10 in parallel good enough for the +12V of the battery? thanks in advance
uh, no 2 10 gauge in parallel isn't enough.

Running 2 wires in parallel is same current capacity as a wire 3 AWG lower. So (2) 10 AWG wires in parallel is equivalent to 7 AWG.

I don't know the exact current when the starter is going, but I imagine it's close to 100 amps. If you go by the ultra conservative electrical code, that's about 2 AWG. I know people who have gotten away with 4 AWG under seat because the code is pretty conservative. I wouldn't go smaller than 4 AWG.

If you want to approximate 4 AWG with 10 AWG wires, you'd need (4) in parallel, and have a good solid connection joining them together.
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Old 07-10-2010, 01:42 AM   #5
JesseL
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I've done this on 3 of my personal cars, and a few racecars, and a few buddies cars.

I used to use 0/1 gauge, but that got spendy, did a buncha math one night, and for 20 feet @ 150amps (Cranking power) at 12v, 2 gauge was more then enough.

I usually go to napa, and its about 3 bucks a foot, comming out to about 60 bucks for the wire.

Also, if you ever plan on running at the track, there are alot of extra rules for running the battery in the trunk, check with IHRA or NHRA for specifics, but 1/2 all-thread mounts, battery isolation switch (THAT KILLS THE CAR, meaning you have to break the alternator wire too), battery box, and so on. I've never auto-xed so I'm not sure what their rules say about it.
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Old 07-10-2010, 02:13 AM   #6
berdugo
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thanks for the help guys

I found a link for AWG sizes and amp capacity

http://www.powerstream.com/Wire_Size.htm

I just need to know the AMPs needed by the starter when cranking but I guess gauge 2 for the +12V plus another gauge 2 for the Bat ground will do.

I'll try to find nice gauge 2 wires here thanks again
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Old 07-10-2010, 11:06 AM   #7
WRX 2002
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I used 2 gauge next time I would go with 4 gauge.
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Old 07-10-2010, 03:47 PM   #8
Patrick Olsen
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2ga or bigger is the way to go. As morocco said, the 0/1ga welding cable is good stuff due to the fine stranding and excellent flexibility. I used 2ga in my Mustang and have never had any problems cranking over a high compression 357ci engine. (Although now that I think about it, "high compression" is the same as the same as the stock CR for the N/A Subies. )
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