I inherited my dad's Alaskan cabover camper.

He had it hooked up to his truck using an approximately 20-foot run of 10-gauge THHN wire and no battery isolator. Needless to say it was always a worry that if we ran stuff in the camper for too long, we wouldn't be going anywhere in the morning. Further, I always thought the connection to the truck was undersized.

I'm about to put the camper on my diesel truck and I'd like to hook it up right this time. I was wondering what battery isolator people recommend, and what gauge wiring I should be using to connect the camper to the truck's electrical system.

Keep in mind this is a telescopic camper and uses the truck's power to operate the camper's hydraulics. I think the hydraulic pump draws about 35 amps at 12 V. That's probably the biggest load in the camper. I ran that through a wire gauge calculator and it looks like I need 8 AWG for that long a run, but I wanted to see what people here thought. Also, I should probably be using stranded wire, not solid (and THHN is for house use anyway, right)?

 

I very much doubt it's 35 AMPS!! That's more than my 30' 5th wheel draws.

 

Alas, I can't find any definitive information, but at 12 volts that's really not a lot of current. That'd be 3.5 amps in a house. It wouldn't surprise me at all if it draws that much raising the roof of the camper.

... and after looking at a few common 12-volt hydraulic pumps, 20 to 40 amps draw is typical.

BPofMd, when you say your entire fifth wheel draws that much, are you talking 12 volts or shore power -- 120 volts?

 

THHN will be perfectly fine, although the insulation is stiffer and there are less strands in the copper core so it's a bit harder to bend than some other options. I would probably look at welding leads or car audio cable since both have a rubber jacket and hundreds of copper stands to hep make the cable bend easier.

As far as an isolator goes, I have no specific recomonendations, but once again you might want to look at the car audio world. Battery isolators are commonly used on high power setups, and some larger ones will easily handle 100A or more (although they may be a bit more flashy than you need). You should connect it pretty much like a starter solenoid except use key on signal wire rather than a start signal for the relay coil; if you want to ensure the truck is running before the isolator contacts close, you could use a zener diode set to somewhere around 13V to make sure the alternator is charging the system.

 

The following link is what I use with my in bed camper. I have a 5th wheel but also a in bed camper for those outings to the deer lease or going to the dirt track for a night.

SurePower 70 Amp Isolator

 

That's sure affordable. I'll put it on my list of things to pick up. Thanks.

 

If your truck has the tow package that includes the 7-pin round trailer connector, you dont need an isolator. That is already included as a relay in the system. I dont remember the pin number, but it is called trailer battery charge. I placed the deep cycle battery for my camper in a plastic battery box vented overboard, but in the coach.

#10 wire is more than plenty. Remember, residential gauge recommendations are based on being enclosed in conduit in the walls, where heat cant be rejected. Open air gauge requirements are smaller.

 

Gaaaaaaah!! I gotta read while my glasses more often!!! I missed the 12v!! Of course my rv is limited to 30AMPS at 120 Volts!!!! My bad.

 

just an information seeking question for my on education.....

Does this slide in camper have it's own battery or does it depend on the vehicle battery for power?

 

The camper does have its own battery. It's also got a 120-volt plugin which will charge the camper battery automatically, and run certain things in the camper like the fridge.

 

trailer plug wire diagram:

 

I found a on Amazon, including one of those automatic isolators that gives charging priority to the cranking battery first. Was wondering what you folks thought of it.

 

That kit is expensive and not necessary if you have the factory tow package, since there is a relay already in your truck, powering pin #4 of the trailer connector.

 

Ok. I'm not sure whether I do or not -- haven't actually received the truck yet. I'll check before buying.

Is there a way to tell from the door tag whether a truck has a tow package?

 

Holy cow--great find! On a 2013 the relay is at location 102, and the 25A fuse is at location 90. I want to add an isolated battery for my amateur radio gear, so it looks like this is just the ticket!