Trailer wiring question

[infinitefoamies]

I am doing a major wiring upgrade on my truck, my dad has a seperate fuse box for the trailer plug to prevent any trailer he tows from blowing the vehicle fuses. I was wondering where I can get a small fuse box like this and what size fuses different things need, such as the lights and electric brakes.

I am also wiring up pollak single pole power connectors to attach the trailers dc system to the vehicles dc system. my trailer has a deep cycle battery and solar panels, I am wiring in a 2000 watt inverter in the truck and a full rv coach system and figure the trailers dc system can help with the load. Should I put a fuse inline of the single pole connector? The inverter has a ground on the input side, where would I attach this?

 

[Gary RV_Wizard]

For a 12v fuse panel, try Ebay or West Marine or a Grainger store. Lots of sizes and types available.  The trailer bulbs run 1.0-1.5 amps each, except the dual filament types like the 1156, which is a tad over 2 amps. Add up the bulbs on each circuit and add 4-5 amps to give some margin.

An inline fuse is a good idea for any power source. If the inverter can pull from the trailer battery as well as the truck, you are going to need real heavy wire, 8 gauge or even 6 gauge, cause the amperage is potentially very high  [Refer to my reply in your other thread about the inverter wiring]. High amps and longer distance means heavier duty wire.

 

[infinitefoamies]

you are going to need real heavy wire, 8 gauge or even 6 gauge, cause the amperage is potentially very high  [Refer to my reply in your other thread about the inverter wiring]. High amps and longer distance means heavier duty wire.

I planned on using 2/0 for the entire run, my dad said 10awg for the trailer battery hookup, but i figure use the same size for the entire run...

 

[Gary RV_Wizard]

That's 2/0 is going to take some humongous trailer connector!

 

[Jammer]

I am doing a major wiring upgrade on my truck, my dad has a seperate fuse box for the trailer plug to prevent any trailer he tows from blowing the vehicle fuses. I was wondering where I can get a small fuse box like this and what size fuses different things need, such as the lights and electric brakes.

I use and recommend Del City for 12v wiring.  They have an extensive selection, good quality, good service, and are cheaper than the marine places.  They have several fuse panels you could use.

http://www.delcity.net/

There are several approaches to overcurrent protection with tradeoffs in complexity, fire safety, and ease of maintenance.  I use self-resetting automotive circuit breakers on the running light (20a) and charge line (60a) circuits and power the running lights through a relay so there is no draw on the tow vehicle lighting wiring.  I also have a self-resetting breaker (30a) on the power line to the brake controller, but not not between the brake controller and the trailer.  I do not add overcurrent protection on the turn signal leads because I believe that what's in the tow vehicle is sufficient by itself.  I do not connect the backup light circuit.

I am also wiring up pollak single pole power connectors to attach the trailers dc system to the vehicles dc system. my trailer has a deep cycle battery and solar panels, I am wiring in a 2000 watt inverter in the truck and a full rv coach system and figure the trailers dc system can help with the load. Should I put a fuse inline of the single pole connector?

I would recommend using a class T inverter rated fuse that is around 20% larger than the maximum rated input current for the inverter.  Here's one source that has good photos and information.  In these sizes care has to be given to mounting and cable management:

http://www.donrowe.com/accessories/fuse.html

The inverter has a ground on the input side, where would I attach this?

You should be using a two-pole Anderson connector and running 2/0 cable for both the positive and negative lines.  The entire circuit, positive and negative, between the batteries and the inverter should be heavy-gauge copper.  The vehicle frame can't be counted upon to carry these kinds of currents.

 

[Jammer]

That's 2/0 is going to take some humongous trailer connector!

It's a fairly standard connector for forklift batteries.  Large, true, but not unmanagable.  It's important to use the finely stranded "welding cable" as the stuff intended for building wiring is too stiff to be workable.

http://www.powerwerx.com/anderson-powerpoles/powerpole-sets/sb350-sb-series-350-amp.html

 

[Gary RV_Wizard]

It's a fairly standard connector for forklift batteries.

Yeah, but they don't dangle out over a trailer hitch. And they are still pretty large vs a typical 4 pin or 7 pin trailer connector.

Definitely need welding cable to handle the flexibility requirement for a trailer hook-up.

 

[infinitefoamies]

That's 2/0 is going to take some humongous trailer connector!

http://products.pollakaftermarket.com/viewitems/connectors/single-pole-connectors

You should be using a two-pole Anderson connector and running 2/0 cable for both the positive and negative lines.  The entire circuit, positive and negative, between the batteries and the inverter should be heavy-gauge copper.  The vehicle frame can't be counted upon to carry these kinds of currents.

you have not listed ground, only positive and negative

 

[Gary RV_Wizard]

The Pollak connector you showed is fine, but its only one of the wires needed. You also need the regular trailer light wires (stop/tail/turn), trailer brake wire, and a negative (ground) sufficient for the whole set-up. A seven pin connector is the norm for travel trailers, but you are substituting the Pollak for part of the wiring.

you have not listed ground, only positive and negative

It's a DC circuit, so the negative is the "ground". Normally the negative ground connection between trailer and tow vehicle would be a lesser gauge, but it need to handle the combined amperage of all the trailer positive loads and so must equal or exceed the largest positive wire.

 

[infinitefoamies]

I have a 7 pin already for electric breaks, signals, etc
i have the two female and wires upto the batteries already that i pulled off my parts truck

the inverter has positive, negative, and ground. i always thought negative was ground, so i am curious where this "ground" should be connected... I understand because of the power the negative should go directly to the battery instead of the frame.

 

[Jammer]

Yeah, but they don't dangle out over a trailer hitch. And they are still pretty large vs a typical 4 pin or 7 pin trailer connector.

Definitely need welding cable to handle the flexibility requirement for a trailer hook-up.

I have one in the next smaller size on the front of my truck for the snow plow hydraulic power pack, which draws around 80a.  Though inexpensive, these are durable, reliable connectors, and because of the material and the contact wiping they are reliable even in road spray, even here where there's salt.  If I put one in for a trailer connector, I'd place a dummy mating connector up out of the way on the hitch frame on the tow vehicle, somewhere, to connect the pigtail to when not towing, so it won't flop around.

Pollack also makes a two-pole (one pole plus ground) heavy duty trailer connector with the same size connector shell as the 7-way we all use, that is rated for 300 amps by the manufacturer, and which accepts 2/0 cable.  They are not expensive though they do cost somewhat more than the Anderson connectors.  The typical application is a rear lift gate on a semi, although Piper aircraft used to use them as a jump starting connector.

http://www.etrailer.com/comparison.aspx?pc=PK11852&pc2=PK11851

Pollack also makes a two-pole connector for 4 or 6 gauge wire, with both poles floating:

http://www.etrailer.com/dept-pg-Wiring-sz-2_Pole.aspx

Either of the Pollack connectors has the advantage of having the "truck end" of the connector designed with mounting ears so that there isn't a pigtail flopping around, and a spring loaded cover to provide at least the idea of protection against water and dirt  (In reality I would expect these to corrode pretty badly after a couple of years if wired so that they're continuously hot.  It doesn't take much dirt to allow electrolysis to take place).

 

[Jammer]

I have a 7 pin already for electric breaks, signals, etc
i have the two female and wires upto the batteries already that i pulled off my parts truck

the inverter has positive, negative, and ground. i always thought negative was ground, so i am curious where this "ground" should be connected... I understand because of the power the negative should go directly to the battery instead of the frame.

I would strongly encourage you to have someone with experience in DC power wiring assist you or review your work before you apply power or connect batteries.

 

[infinitefoamies]

i guess this same issue pops up with tandem trailers; when you have a slide in camper and are towing a trailer, do you wire the harnesses for the lights in parallel?

 

[infinitefoamies]

anyone know the current limit for a 7 way blade style trailer connector?
im assuming the round pin "7" can carry more than the rest?

 

[Mopar1973Man]

I wouldn't suggest more than 30-40 amps. At least that what my Dodge Ram is fused fore on the 7 pin plug.

 

[Brother Bear]

My Ford F-350 has a 30 amp superfuse on the B+ pin at the trailer connector. 10 gauge wire is sufficient. I don't believe I'd want to subject the truck system to more than that on a charge line. It's enough to keep the battery bank charged while running an 800 watt power inverter on my fridge on the road.

The only problem I have with the 30 amp is if I forget to shut the truck off and/or unplug the trailer while operating the electro/hydraulic landing gear. That will blow the fuse.

 

[infinitefoamies]

I am debating setting the camper up to take its dc power through the trailer light connector or the pollak connectors and if i should upgrade it to a 30amp ac system.

It has a small window ac unit, i have not been able to determine how the appliances and lights are powered when they are not on fuel/ where they get power if any of them work off of dc.

 

[Brother Bear]

Most lights work off of the 12V system. So do most furnaces. If your fridge is not of the residential type, it should work off of 12V and propane or 120V. Your water pump should also be 12V. Other than that, unless I missed something, microwaves, AC units, water heaters, etc. should all require 120V from a generator or a shoreline. Some things with lower requirements may be run off a power inverter which will require good 12V power input.

 

[John From Detroit]

A simple fuse block, you need what, at the most 5 fuses, can be found at most electronics stores.. These usually take 3ag fuses (Glass cartridge)  You can also find them at some Truck stops if I'm not mistaken, or CB shops. but any electronics supply will have them.
Link 1

Link 2

Both links are to blade type (ATO/ATC) fuse holders, multiple socket.