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Battery cable gauge question

4K views 6 replies 6 participants last post by  KF4SQB 
#1 ·
Im relocating my battery and was wondering what size wire i need. I read somewhere its a 6 gauge wire but when i looked at Lowes their 6ga wire says its only 65 amps, any thoughts or suggestions would be appreciated! thanks..
 
#2 ·
The longer the distance, the larger the wires should be. Fine strand wire cables are better conductors than cable with fewer/thicker stands of wire.

Under the hood 6 gauge or 4 gauge is an OK upgrade. Longer distances will need thicker wire.
 
#4 ·
The answer will depend on where you are relocating your battery. Under the hood, all of my Cherokees have run 1ga. My TJ runs 00ga. All of my "extra" grounds to the primary spots are the same size. If you are relocating to the rear of the vehicle, 4g or 6g will be inadequate. You will need to be substantially larger.
 
#5 ·
If you ever plan on using a high-draw item (think "winch") save yourself some grief and go with 2/0 welding cable. It's designed to carry 300+ amps all day, with very little chance of burning up under the load.

I've got welding cable running to both ends of my rig & 350 amp plugs on each end so I can winch off either end of the rig (or use the jumper cables I built with a plug on one end). A little heavier than lighter gauge cable, but will take anything I can throw at it. (and I had a bunch that I bought years ago to make battery cables with)
 
#6 ·
Yeah you can get some reasonably priced small lengths Welding cable on ebay fwiw
 
#7 ·
If I understand correctly, you are saying that you have 2 ga. on the positive. If you put anything smaller than 2 ga. on the ground, you wasted your time putting a 2 ga. on the positive. "What goes in, must come out." Also, 6 ga. is a joke for a battery cable on anything bigger than a lawnmower. Don't waste your time. When it comes to battery cables, bigger is definitely better. Personally, I currently have 4/0 welding cable as the battery cables on my XJ. Consider this: your starter can easily pull in excess of 200 amps during a start cycle. Now, I know what you are thinking at this point. "But the 2 ga. cable on here now works fine, and its only rated at 115 amps!" You are correct, but to understand this, it helps to understand how wire ampacities are actually determined. I'll give you the short version. Wire is not actually rated for how much current it can carry; it is rated for how much heat the insulation can handle. It would take over 200 amps to melt 12 ga. copper wire, but it is only rated for 25 amps. This is because the insulation can only safely withstand the heat generated by the wire carrying 25 amps. However, this doesn't mean that the insulation will instantly fail if you run 30 amps through the wire. It might be possible to safely run 30 amps through 12 ga. copper for 1.5 minutes (I'm guessing; I don't know an exact figure) before the insulation fails. Also note the the wire ampacity ratings are based on the type of insulation on the wire. For example, THHN (an insulation type) is rated for use in a 90 degree C environment, and a #6 wire can safely handle 75 amps. On the other hand, #6 TW (a different insulation type) can only safely handle 55 amps, and is rated for a 60 degree C environment. Wire ampacities is a very in depth subject, with a lot of variables to take into account. Personally, I would use nothing smaller than a #2 for battery cables under the hood of a vehicle. If you are planning to relocate the battery to the cargo area of an XJ, I would use nothing smaller than 4/0.

@CJ7-Tim: You are both correct, and incorrect, about finer strands being able to handle higher current. For AC current, yes, finer strands are definitely better. For DC, the size of the strands is largely irrelevant. However, for automotive use, yes, finer strands are better, due to better stress resistance, meaning that it can take repeated flexing and vibration much better than coarser strands. To make things even more confusing and hard to keep up with, the ratings everyone goes by, which are provided by the NEC (National Electrical Code, published by the NFPA [National Fire Prevention Association]), are for AC current. You can safely pull more DC current through a given wire than you can pull through the same wire with AC, due to a phenomenon known as "skin effect". This is why individual strand size is not as important at DC as it is at AC. Also, yes, I do just happen to be an electrician. Cheers!:cheers2:
 
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