Electric Brakes For 8FT Taos

[JimQPublic]

I wouldn't trust any local Uhaul to touch the vehicle's electrical system.  I suggest going with:

Eckhart's Trailer Hitch & Welding Inc
Los Angeles, CA 90025
(310) 479-1298

They made a custom Class III hitch for my Subaru and did great work.  About 80% of their business is hitch and wiring work for late model vehicles.  Buy the Prodigy and have them install it.

I didn't have them do the electrical work but I would trust them.  I doubt that your Mitsubishi dealer would have any experience putting in a brake controller.

Also I didn't see mention of the breakaway switch.  If you trailer doesn't have one it will need to be added.

While you're doing the brake controller it's a good idea to add a charge line, relay, and circuit breaker to charge the trailer battery from the tow vehicle.  Insist on heavy gauge wiring- #4AWG battery cable is about $1.25/foot at a battery supply place.

Also make sure they connect the ground wire from the 7-pin connector directly to the car chassis.  The stock wiring harness ground wire for the trailer lights is not sufficient to handle the increased load from trailer brakes and charge line.

Jim
Long Beach

[rb_beachcpl]

Our local Uhaul shop does not do brake controllers, so I will give Eckhart's a call. I just want it done right. I don't trust myself to do it. Everything I touch falls apart. Setting up the kid's bicycles on Christmas Eve was always a nightmare!

Thanks again.

[AustinBoston]

Insist on heavy gauge wiring- #4AWG battery cable is about $1.25/foot at a battery supply place.

Just a bit of overkill for a cable that is going to be breakered at 25 or 30 amps, don't you think?  #4AWG will handle 200 amps!  Anything less than #8 is not adequate, though.  #10 is rated for the current, but what's important is the voltage drop, and to keep that down you do need to go to #8.

Austin

[JimQPublic]

Just a bit of overkill for a cable that is going to be breakered at 25 or 30 amps, don't you think?  #4AWG will handle 200 amps!  Anything less than #8 is not adequate, though.  #10 is rated for the current, but what's important is the voltage drop, and to keep that down you do need to go to #8.

Austin

Austin,

I think #4 is only slight overkill.  I actually did my car with #6 extra fancy tinned boat wire from West Marine.  The #4 battery cable is cheaper though.  As you pointed out the important issue is voltage drop.  If you have batteries discharged and you want to quickly recharge them while also running the fridge on DC, even a few tenths of a volt drop is going to significantly slow the charge rate.  Also by having stout cables with soldered lugs the voltage regulator won't be tricked into reducing output based on a fully charged starting battery in the car.

The vehicle and trailer configuration obviously make a difference.  In my case my car is only 15' long but it took 22' of cable from the alternator to the 7 pin connector.  In the trailer my batteries are in the very back opposite the side where the connector comes in so I had another 20' of cable there.  I used #4 on the trailer.  I have a 40 amp circuit breaker and a relay near the alternator as well as low resistance 60 amp fuses on each end of the wiring in the trailer to protect against problems from a short in the batteries, cable, or converter.  

My results don't lie.  I have gone from four nights of dry camping where I used about 100 amp hours, then drove 150 miles from Sequoia to Yosemite while running the fridge on DC.  A few hours after arrival tested the battery voltage and it indicated 100% charge.  Most people claim that you can't expect to recharge the batteries while running the fridge.  That's because with #10 or #12 wiring, weak ground, and poor connectors you just get too much voltage drop.

I don't see any real downside to the heavy wire orther than the risk of a catastrophic short.  That's why I used fuses at the battery and converter in addition to the circuit breaker.  The maximum charge rate will be limited by resistance from the 8' of #10 wire in the trailer end 7 pin cable.

[AustinBoston]

My results don't lie.  I have gone from four nights of dry camping where I used about 100 amp hours, then drove 150 miles from Sequoia to Yosemite while running the fridge on DC.  A few hours after arrival tested the battery voltage and it indicated 100% charge.  Most people claim that you can't expect to recharge the batteries while running the fridge.  That's because with #10 or #12 wiring, weak ground, and poor connectors you just get too much voltage drop.

Anybody else find this claim just a little suspicious?  At 50 MPH avarage (3 hour drive), that would require a continuous 43 amps (assuming the charge rate is constant, which it would not be).  My tow vehicle has a relatively large alternator capable of putting out 120 amps.  But I know there is no way it has 43 amps left over for my trailer - at least not continuously.  It (and I'd bet yours) is not designed for that kind of current on a long-term basis.

I hope you don't end up damaging your TV battery using it to charge your camper battery like that!

Austin

[JimQPublic]

Anybody else find this claim just a little suspicious?  At 50 MPH avarage (3 hour drive),
Austin

Okay you caught me.  I don't have a Trimetric or anything like that to monitor power consumption.  I was just guessing at the depth of discharge after four nights in cold weather of furnace and lighting use.  It's possible to have been far less.  

Also I just double checked the map.  Mileage is about 180 and I imagine the average speed was probably about 35, so 5+ hours drive time.  The road from Giant Forest in Sequoia National park to Yosemite Valley via Fresno has a lot of slow mountain driving.

Still, we frequently do trips where we dry camp a few days in one spot then drive a few hours to another.  I usually run the fridge on DC while driving since it usually blows out on propane.  I've never seen less than 12.6 volts on the dual trailer batteries after arriving.

[AustinBoston]

I guess your assumptions + my assumptions = too many assumptions.  Still, I would suspect you may be drawing current from your TV battery when you first hook up.  If your charge line is hooked to the TV starting battery, then you would probably have to draw current from it to keep the voltage down enough to not "trick" the alternator into backing off based on the starting battery.  I don't know how I would test for this; I also don't know if it really would cause damage.  It would depend on how often and how deep into the TV battery charge you went.

Just something to think about.

Austin

[JimQPublic]

I guess your assumptions + my assumptions = too many assumptions.  .... If your charge line is hooked to the TV starting battery, ...
Austin

You know what they say about assumptions.  This is getting way off the original topic but I'll keep going.

My old tow vehicle ('96 Subaru Outback) had a pretty standard charge setup with 10AWG wire- I had my trailer dealer wire it up for brake controller and charge line.  It worked fine but when we got the new vehicle (2004 Subaru Forester) I decided to go all out.  Everything I read here and on places like RV.net implied that you couldn't expect trailer batteries to get much charge while driving.  I came to the conclusion that voltage drop caused by resistance in the system was the main problem.

My wiring job was designed specifically to reduce voltage drop.  I went with heavy cables and quality connectors- all crimped, tinned, soldered, and sealed with marine grade heat shrink.  Instead of connecting to the battery I tied to the outpost of the alternator.  I also ran an unbroken ground cable from the alternator frame back to the trailer plug.  On the trailer side I used similar procedures.  The fuse holders are high quality car audio models.  Although I used cheaper wire there (Auto battery cable instead of tinned marine grade), I still crimped, soldered & sealed.

I just used a standard relay, not one of the Wrangler time delay models.  I did trigger it from a switched accessory circuit so that it shuts off while the starter is engaged.  I didn't use the common practice of tying into the winshield wiper circuit- The book "Road Fever" by Tim Cahill talks about losing the wipers in a Rainstorm on a narrow road in the Andes after some aftermarket equipment shorted out.

In all I spent a small fortune to set the Forester up for towing, including almost $300 for electrical components.  I even had a custom Class III hitch made.

It might have been overkill.  Certainly a 60 amp multistage battery charger and Honda EU1000 generator might have been a better way to ensure the batteries get charged.

Pardon me but I have to head out to spend the weekend camping with my 3 year old.

Jim

[AustinBoston]

Pardon me but I have to head out to spend the weekend camping with my 3 year old.

That's more important than anything I have to say!  

Austin