Running 12V power to the bed

I plan on adding a Blue Sea 5025 to the engine bay and one in the corner of the bed near the 110 outlet. My question is, what size wire should I use to supply power to those and do I need an in-line fuse running to them?

$34 Blue Sea Systems 5025 ST Blade Fuse Block 6 Circuit with Ground and Cover

Blue Sea Systems ST Blade ATO/ATC Fuse Blocks

These are what I'm using if that matters.

 

Yes you need a fuse.
The size will depend on the amount of amperage/current you expect draw.

There are many charts and calculators online to help you choose the wire size
Here is just 1 of many - https://faroutride.com/wire-calc/

 

You want something like this: https://www.solar-electric.com/mrcb-80-amp-dc-circuit-breaker.html

I'd put them closest to the battery. I would probably run 8ga wire

Edit: ^^^ that's a cool site, looks like they say 6 for a 15 foot run with 50 amps load, but 8 for a 30 amp load. I'd like to change my answer to 6awg then

 

I would also look at your amperage load and make sure you aren’t pulling more amps than the alternator can keep up with. If you do you’ll drain the battery.

 

So I should probably elaborate. The power in the bed will only be for a USB hub wired inside of an RTT to power a small light strip and cell phone charger. The fuse box under the hood is just to cleanup the wiring for lightbar, ditch lights, and horns. I was thinking 8GA would be fine but wanted to make sure before ordering.

 

Doesnt the tow package alternator have a slightly higher output? or does it just use a bigger fuse?

 

Slightly more output.

8ga sounds more than adequate for what you're thinking. Go 6 or 4 if the potential to draw more power someday exists.

Get copper, not "cca" wire.

 

Yes. I think the stock unit puts out 130 amps. Remember that they limit the plug to 400w (33 amps) when in park and only 100w (8 amps) when driving so it won’t tap into the battery.

 

I think you calculated backwards. 400 watts at 120v is 3.3 amps and 0.83 amps at 100 watts.

 

Calculate the total load and any starting currents. Then measure the distance. Round up to next wire gauge. It will be bigger than you think because it’s DC.

 

I ordered 25ft of red and 25ft of black 100% copper 6 ga

 

Sheesh (beer) lunch is on you. What's next, a brick of .22 and a crank for the rifle? Mercedes pickup or SUV?

Remember a good breaker for under the hood, you don't want to cook a long wire run and the big fuses are a PITA if something happens and you're hours away from everything.

 

Lol it wasn't cheap but figured I'd use it elsewhere. I ordered 60a in-line fuses as well. You mean a kill switch or an actual breaker on top of the fuses?

 

An actual breaker, they're quick to trip but easy to reset without looking, digging, or being pissed you can't find the (mini/maxi) ATC fuses you bought specifically for one application.

They also give you studs allowing you to be a bit more OCD with your install.

It's $20-40 well worth it for convenience and simplicity.

 

So fuck the fuses, just run a breaker? I figured 60A would suffice or would you go bigger?

 

In the truck I used a 60A cause it was sitting in the shop gathering dust. I'm running an 18A on tx radio, maybe 4A of lights and the siren draws 7-9A.

In the Jeep I used a 120A, but it's still mostly to protect the wire in case of damage in the field/on the trail; also more radios, more lights.

The upside: you can always trade/swap breakers for something bigger.

The fuses are decent, I just avoid them to avoid the drive back to anywhere without the fun stuff. You can always fuse the ground side (good ham practice).

 

Agree, close to the battery. That way if road vibrations causes the wire to wear through and short to ground, the breaker will actually work.

Here's a picture of how NOT to do it, thank you Ford. That’s all the way in the far back right behind the air compressor (that doesn’t have an alternator so it needs to be attached to the vehicle battery). There is a secondary battery in the battery box. Primary battery is under the drivers seat, thank you again ford.

 

I was thinking of the source side from the alternator at 12V realizing that I wasn’t taking in account the reduction for the transformer. I still could be wrong though.