Running power to bed from battery. How to use aux switch so not always hot?

[antwon412]

I am going to run a length of 10 gauge positive and negative wire from the battery to the bed terminating in an Anderson connector for my portable ARB air compressor.

I would like to tie it into Aux switch 1 or 2 (40 amp switches) so I can control when it is hot.
I am having a hard time wrapping my head around how I’m going to do that. I don’t think I can run the negative straight to the battery and the positive to the switch 1 wiring in the engine bay can I?

EDIT No way. At quick glance the ends look like 18 or 20ga wire

I did buy a 40 amp circuit breaker to use just in case I do go straight to the battery.

Thanks.

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[22EcoDs]

Yes you can

 

[Mr._Bill]

What is the draw of the compressor? If less than 40 amps, you'll be okay. It is better to run larger wire than needed to compensate for any voltage drop, and heat generation that can result from long run times. It is not necessary to run the negative wire, a good frame ground near the mounting point will work well.

 

[antwon412]

What is the draw of the compressor? If less than 40 amps, you'll be okay. It is better to run larger wire than needed to compensate for any voltage drop, and heat generation that can result from long run times. It is not necessary to run the negative wire, a good frame ground near the mounting point will work well.

Current draw under load is 23 amps.
Its the CKMP12 setup.

Single compressor in a toolbox basically.



Thanks everyone.

 

[WILDHOBO]

I am going to run a length of 10 gauge positive and negative wire from the battery to the bed terminating in an Anderson connector for my portable ARB air compressor.

I would like to tie it into Aux switch 1 or 2 (40 amp switches) so I can control when it is hot.
I am having a hard time wrapping my head around how I’m going to do that. I don’t think I can run the negative straight to the battery and the positive to the switch 1 wiring in the engine bay can I?

EDIT No way. It’s like 18 or 20ga wire it looks like.

I did buy a 40 amp circuit breaker to use just in case I do go straight to the battery.

Thanks.

You absolutely can. And switch 1 and 2 are closer to 12awg, if not 10. Using 10awg is a great way to avoid loss on the run to the back, but the wire size under the hood is perfectly fine for 12v 40amp. Loss on the length of the run is important to consider, but this isn’t 120v or 240v 40amp. It’s 12v. Even high voltage (120, 240) 40amp only calls for 8awg, depending on run length. I’d also recommend running down the passenger side if its a 3.6 to avoid the exhaust heat.

 

[kooltoys]

would wire a relay on the positive cable and use a lower amp aux switch to trigger the relay

 

[Josh00333]

Depending where you outlet will be there is a ground behind the spare tire, you don't have to run the ground all the way back.

 

[dcmdon]

If the switched circuit is rated for 40 amp and the pump draws 23 amps you are good to go.

But you can also make the long run work better by using thicker wire. Remember that a wire's resistance is proportional to its length and inversely proportional to its cross section diameter.

So if the switch has a smaller ga wire, it still makes sense to splice it to a thicker wire for the run to the bed. Feel free to put an in line fuse but I also believe that the switched circuits have fuses already.

Loss on the length of the run is important to consider, but this isn’t 120v or 240v 40amp. It’s 12v. Even high voltage (120, 240) 40amp only calls for 8awg, depending on run length. I’d also recommend running down the passenger side if its a 3.6 to avoid the exhaust heat.

Everything you said is right. But you seemed to imply that voltage has some relevance when it comes to choosing wire size. It does not. Wire size is requirements are entirely determined by amperage or current.

 

[Rockabillyroy]

If you're running it to an anderson powerpole and it'll only be used while plugged in, I wouldn't bother with switched power. I would just make sure to put a fuse by close to the battery.

I had an powerpole pigtail that ran from the battery to the cab in my old JKU. Used it for a portable compressor and a small inverter.

Both those items had their own switches for power.

 

[WILDHOBO]

If the switched circuit is rated for 40 amp and the pump draws 23 amps you are good to go.

But you can also make the long run work better by using thicker wire. Remember that a wire's resistance is proportional to its length and inversely proportional to its cross section diameter.

So if the switch has a smaller ga wire, it still makes sense to splice it to a thicker wire for the run to the bed. Feel free to put an in line fuse but I also believe that the switched circuits have fuses already.



Everything you said is right. But you seemed to imply that voltage has some relevance when it comes to choosing wire size. It does not. Wire size is requirements are entirely determined by amperage or current.

It’s similar, but not identical to high voltage. In 120 or 240, 8awg is called for in 40amp applications even for very short distances. The 40amp aux1/2 switches are not wired with 8awg from the factory.

 

[dcmdon]

It’s similar, but not identical to high voltage. In 120 or 240, 8awg is called for in 40amp applications even for very short distances. The 40amp aux1/2 switches are not wired with 8awg from the factory.

I'm 90% sure that is a result of AC vs DC voltage. Do you have any documentation explaining why voltage matters. Because that goes against everything I've learned.

 

[Deleted member 22728]

Relay the circuit off of switched power.

 

[WILDHOBO]

I'm 90% sure that is a result of AC vs DC voltage. Do you have any documentation explaining why voltage matters. Because that goes against everything I've learned.

http://www.offroaders.com/technical/12-volt-wiring-tech-gauge-to-amps/

This chart shows you can draw 50 amps at 10ft of length using 10awg. If the OP is hooking up a 25amp draw appliance to aux 3 or 4’s 10awg positive wire, he’s fine running 10awg. If 50amps were being drawn on 120v or 240v, it would call for 8awg.

 

[OHJeeper]

would wire a relay on the positive cable and use a lower amp aux switch to trigger the relay

THIS

Use a relay, they're cheap insurance

 

[WILDHOBO]

THIS

Use a relay, they're cheap insurance

Nothing wrong with a relay, but if you’re hooking up something using less than 40 amps and you have a switch to spare, there is already a relay and fuse wired into that circuit.

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