Size of wire for a 12 volt run.

[chevy]

When the contractors cap was installed on my truck, they ran small fused power & ground wires from the battery back to the cap for interior lighting. I am now installing air bags on the rear axle. I am installing a small compressor in the cap to operate the air bags.

The compressor also requires fused wiring to be run to the battery for power.

Many times I would have like to have had access to 12 volt outlets at the back of the truck for different things.
Instead of having several wires running from the battery to the back of the truck, I am considering running 2 larger wires.
One fused line for the power & one for the ground. I would then put a ganged fuse block in the cap. The block I have found is rated for a total of 65 amps & has 6 separate fused power connections.

The problem I am having, is the size wire I need to make the run from the battery to the rear. The run is about 25 feet.
I have found several charts online, but they do not agree. Some charts list wire length as total of hot & ground & others just give a length. Wire sizes are all over the place.

I need help.

 

[Diamondpilot]

I would run 8 ga minum, 6 ga would be better. While you are putting 65 amp fuse block in place most likely you will never run more than 2 items at a time. So let's say your compressor takes 30 amps to start and you have a 10 amp load plugged into the power port you would be fine.

Chris

 

[George2615]

Do you think you will be drawing the full 65 amps from your in cap fuse block? At 65 amps you would need 4 ga. wire for a 22-28' run. How many amps does the air compressor draw on start up. I had an air ride system on a classic car years ago and the compressor was in the trunk. It only required 10 ga. wire to operate. If you mount the fuse block closer to the cab you would need less wire to feed it and can use a smaller gauge. What sizes are the fuses in the block you will install and will you use more than one circuit at the same time. I'd suggest 8 ga. wire since I don't think you'll be using more than two circuits at the same time.

http://www.arcomarine.com/xhtml/Tech Wiring,Voltage,Sizes.pdf

 

[Diamondpilot]

One other thing, make sure you put a Fuse or Circuit breaker at the battery. If i was doing this I would order a 50 amp car stereo amplifier kit off Amazon or Ebay. You will get everything you need other than the distribution block you want to add and it will be quality stuff at a reasonable price.

Chris

 

[k0ua]

One other thing, make sure you put a Fuse or Circuit breaker at the battery. If i was doing this I would order a 50 amp car stereo amplifier kit off Amazon or Ebay. You will get everything you need other than the distribution block you want to add and it will be quality stuff at a reasonable price.

Chris

Amen, Be SURE to fuse it at the battery, because if you run a large gauge wire back to a fuse block back in the cap, and you have the positive wire rub thru to the vehicle chassis.. LOOK OUT for the fire and the smoke.. and I am not kidding.. I have seen it happen. In a police car installation I saw where an installer did not fuse the wire running to the trunk for the radio equipment, and one day a deputy sat a prisoner in the back seat. Well the edge of the seat finally pierced the insulation of the positive wire.. The wire started to smoke the carpet almost instantly, the prisoner reportedly started screaming about the smoke, and the deputy actually had the presence of mind to grab a tire tool, and pry the connection off of the positive terminal of the battery before the whole car caught on fire (it was all he could lay hands on at the time). I did not make the installation but I sure saw the damage and rewired it.

 

[Travelover]

My local metal recycler has all kinds of new braided THHN wire (ends off long rolls) that he sells for a fraction of what you'd pay retail. I'd use 6 or 8 gauge and fuse it right at the battery.

 

[chevy]

Thank you for the replies. I will have a fuse at the battery. I will go with 6ga wire just to be safe. I will also be running the wires through a loom so they will be protected

 

[Fordman1981]

Thank you for the replies. I will have a fuse at the battery. I will go with 6ga wire just to be safe. I will also be running the wires through a loom so they will be protected

If you have an iPhone check out an app called battery run time. It has a voltage drop calculator. It'll tell you what voltage drop you will have with each wire size selected.

 

[chevy]

Work has kept me too busy to get any thing done on the truck wiring yet.

I am still trying to decide on how I want to do it.

Has anyone used one of the Blue Sea Systems 187-Series Surface Mount Circuit Breakers. They serve as both a switch & breaker.

Amazon.com: Blue Sea Systems 187-Series Surface Mount Circuit Breaker: Sports & Outdoors

 

[k0ua]

No, but they sure look nice. Maybe a little expensive, but good stuff often is.