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Wire gauge question


Tim240z

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For the power wire that goes from the alt. to the battery (charging wire), is 10 gauge large enough? I figure that it is probably ok, and I have plenty of it, but I'm using 2 gauge battery cable and the 10 gauge wire just looks SO puny in comparison.

Any recomendations?

Thanks,

Tim

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Guest greimann

Lets work it out. If an alternator is rated at 100 amps, and it has to put out its full capacity to charge the battery and run systems (worst case). 100 amps X 12 volts = 1200 watts. According to the table in the link below, a 3 foot length of 10 gauge is good for 1200 watts. If your alternator is rated for less than that, all the more safety factor. If you have a 100 amp alt. and have a 5' wire run, then better go with 8 gauge.

 

http://www.rbeelectronics.com/wtable.htm

 

Batteries have the capacity to supply over 500 hundred amps of current and frankly 2 gauge seems a little puny. I think I would find some 0 or 00.

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The 2 gauge is actually wayyy bigger than the OEM Z28 stuff, so I'm not worried about that. The alt. is oem Z28 (LT1), which I think is about 65 amp or so. I am needing about 5 feet to the kill switch (battery side obviously), so I think I will just go ahead and get some 8 gauge.

I am assuming that the cable is 2 gauge 'cause that is what the end terminals were stamped. I got the relocation kit (although I wont be using the box) from summit:

sum-g1200a.jpg

 

The cable is pretty stout and has LOTS of strands so it's pretty flexible and seems to be very nice quality.

 

Thanks for the responses.

Tim

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Hey Tim that Summit kit you have pictured is the kit that I used to relocate my battery into the spare tire well on my 72'. I have not had any problems with the gage of the wire they sent me, my car cranks over immidiately all my accesories power up just fine and I have not found any indication of the wire getting hot or over loaded.

 

Dragonfly

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Scottie (or anyone),

I just installed a Taylor vented alum. box and was wondering do I now need a way to shut the car down from the rear. I bought a master cutoff switch and was going to run a rod from the rear and just remove it while not at the track. I only go to the track on test and tune nights but I wonder that once I relocate the batt do I have to do the whole 9 yards in order to get on the track.

The lady on the phone at Darlington intl raceway didn't tell me much and said i should come one night and talk to the tech guys. thanks for any help guys.

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Yes, you must have a shutoff switch connected to the HOT side directly off of the battery. I did it on th eground side and the ground at the alternator is enough to keep the car running when the switch is thrown :( I need to put a relay up front at the alternator I guess. IF you do the HOT side you won't have this problem if the alternator juice goes through the switch too. Downside to this, IMO, is that if your car is ever struck from behind in an accident that switch is VERY likely to ground to something - right on top of the danged fuel tank! :( The onlyplastic box "certified" BTW is the big blue Moroso unit and that only recently approved. Boat boxes don't cut it, the aluminum and zinc coated ones do. Zinc units aren't sealed though so Moroso or aluminum sealed is the right way to go on the Z IMO.

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Thanks BLKMGK,

 

I think I'll run a small hot wire from the bat straight to the ecm and radio, so they won't lose their memory if someone wants to see what the big red button that says "PUSH OFF" is for. thanks again, later.

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I'm getting ready to install a remote battery cut off switch. I bought the heavy duty Moroso one, with the alternator cut out, and a lever/rod extention kit for it. I'm going to need to lengthen the rod that activates the switch, as I want to mount the switch right next to the battery box where the pos wire comes out. That's right at the front of the package shelf in my car. If you do a switch with a remote rod/lever setup, the switch is away from the back of the car and the issue of sheetmetal shorting it goes away. Plus I plan to only run the rod out the back when at the track.

 

Although I'm using 2 gage wire for the battery (never been a problem, but my battery is just behind the passenger seat on the package shelf), I run 8 gage for the alternator. You don't want voltage drop from the alternator to the battery or the battery won't ever get a full charge from it. I'd go 8 gage at least with a remote battery switch setup, as your going to have 10 plus feet of wire between the alternator and the battery, unless you use a relay. And a 100 amp relay is not small. Probably the easiest thing to do is just use another Ford remote "solenoid" contactor and have the alternator terminals on the remote cutoff switch operate that. Mount the Ford contactor between the alternator and the battery so you aren't adding more length to the high current charging wire. Let the 18 gage wire from the battery cutoff switch to the Ford contactor's "start" terminal be long instead.

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Pete,

I don't understand all the effort to put in solenoids, relays etc on the alternator output. Why not just run the alternator wire to the battery terminal of the main switch. That way when you turn the switch to off, all the current to the ignition is stopped and any excess current being discharged by the alternator is just going directly to the battery. Am I overlooking something critical here, 'cause that is how I have mine wired.

Tim

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I have one wired in now, and it's installed inside the car for me to use as a safety device and an anti-theft device. It just disconnects the big battery cable, and the alternator would continue to let the car run. The second one I'd put in would be for drag strip purposes, and wire in the alternator output cutout part as well.

 

The issue with the remote switch that does disconnect the alternator output separately from the battery and the electrical system is that you end up running alot of alternator output wire to do it. I'd use at least 8 gage if I were to run the alt output all the way back to the remote switch.

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