Upgrading trailer’s 4-pin to charge the trailer’s battery

[Karl]

I was wondering if someone could point out another thread that discusses what I am trying to accomplish below.
Thanks!

My 2008 Jeep Wrangler has a 7-pin hookup on the back. My Little Guy 6-Wide has a 4-pin that I currently connect to the Wrangler’s 7-pin via an adapter. The trailer battery sits on the tongue and does not currently get charged unless I hook up a separate battery charger.
I have two goals in mind.
First is to have the trailer battery get charged by the Wrangler while on route to the campground.
Second is to have a 12V receptacle hooked up to the trailer battery so that my new Waeco CF-40 12V cooler can be plugged in and running off of the trailer battery when not around AC power.
Related to goal #2 and as an aside in case anyone is looking for an interesting product, I just ordered from JCWhitney.com a trailer adapter (item # ZX298682) http://www.jcwhitney.com/autoparts/ItemBrowse/c-10101/s-10101/p-100000380001/mediaCode-ZX/appId-100000380001/Pr-p_CATENTRY_ID:100000380001. This device plugs into the 7-pin on the towing vehicle and then allows for a 4, 5, and/or 7-pin to plug into it. Thus, instead of using the 7-to-4 pin adapter mentioned above, I can just plug the 4-pin from the trailer directly into this device. The main reason I bought it, though, was because it has two 12V receptacles on it so that I can have my new Waeco cooler plugged in and keeping my camping food cold while heading to the campground. For $33.99, this seemed like an easy and less expensive way to accomplish goal #2 than to have an RV dealership hardwire something for me. However, this would be using power from the Wrangler, not the trailer battery. Since the Waeco cooler claims to be able to shut down the cooler if it senses the 12V power source voltage is getting too low, maybe I shouldn’t be to concerned about draining the Wrangler’s battery when the engine is turned off…but I don’t know. For most scenarios where I will be driving straight from home to a campground, I generally don’t need to worry about the Wrangler’s battery being drained.

Is changing the trailer wiring from 4-pin to 5-pin (in order to get the trailer’s battery charged by the towing vehicle) going to be very difficult to do? I assume we’re just talking about hooking up a couple heavy-duty wires between the 5 pin and the trailer battery but would I also need a fuse in there somewhere too? Should I go from a 4-pin to a 5-pin or should I just put in a 7-blade round even though I do not have trailer brakes nor backup lights? Do my questions indicate I should have this professionally installed? <g>

Thanks!

[bobhenry]

Good to see ya back on the forum.

After 2 1/2 years as a U haul center manager and responsible for my hitch mechanics work on several hundred hitch and wiring installations I have a little insight.

If you have a U Haul company owned center close by have them install your 7 way round on the Jeep and convert the 4 way on the trailer to a 7 way. The contacts in a 7 way are much larger and more easily able to handle full battery current. They will also install a breaker at the tow battery to protect the circuit. I have a 7 way on the Grand Wagoneer and have never had a minutes trouble with it and 4 ways on 3 other vehicles and all have been a PITA from time to time

[Karl]

If you have a U Haul company owned center close by have them install your 7 way round on the Jeep and convert the 4 way on the trailer to a 7 way. The contacts in a 7 way are much larger and more easily able to handle full battery current. They will also install a breaker at the tow battery to protect the circuit. I have a 7 way on the Grand Wagoneer and have never had a minutes trouble with it and 4 ways on 3 other vehicles and all have been a PITA from time to time

Bob, I should have known I could depend on you...especially since Vickie has always said you know EVERYTHING!
That was a good point I was unaware of regarding the contacts on a 7-way being better able to handle the full battery current. I'll do the breaker at the tow battery too. Just to make sure I clearly convey this to the UHaul people, you are talking about a breaker, not a fuse, right?

The trailer came with a Worldwide Battery model 24DC-4, which has 595 marine cranking amps and 115 minutes of reserve capacity @ a 25 amp draw (whatever the heck all that means). I don't know if you have enough data to answer this question, but ... Once everything is wired up properly so that my Wrangler is charging the trailer's battery, would a 2-3 hour drive typically be enough for the tow vehicle to recharge the trailer battery (assuming it was discharged enough to no longer be able to run 12V lights in the trailer) or am I better off always putting the battery charger on the trailer battery overnight before the trip because it will take a lot more than 2-3 hours to charge the battery? While driving, would the fact that I would be drawing 45 watts for that Waeco cooler through the adapter I mentioned from JCWhitney make a difference in your answer?
What type of cold cereal does Vickie want me to bring to Chain O' Lakes??? I wouldn't want you two to starve at breakfast time.

BTW: What does "PITA" mean?

Your PITA friend from Michigan,
Karl

[bobhenry]

Do not run the battery to the point that it will not light a light you will kill it in short order. Others need to help here but I think once you see about 10 volts ???? you need to stop torturing the battery and recharge. You might get a volt meter at an auto supply house and have it installed to monitor battery health.

And yes it is a resetable breaker ! and the battery should charge
in the first 30 minutes of driving provided you did not totally drain it
( see above)

PITA thats not the bread it's "Pain In The Ass"

Cold cereal real men don't eat cold cereal but I would settle for a big bowl of hot oatmeal and about a pound of bacon. That will give ol' what's her name something to do !

[firemaniac]

You say your Wrangler already has a 7 pin RV connector on the back? Ground a test light somewhere, I would be willing to bet that the Jeep has a hot wire for the trailer already (at about the 1:00 position). if so that side is done.

For the trailer side purchase a 7 pin connector, a length of heavy ( at least 8 gauge) black wire, and a length of heavy ( at least 8 gauge) white wire, appropriate connectors, and a 40 amp circuit breaker.
Mount the circuit breaker near the battery, run the black wire from the 7 pin connector to the circuit breaker, and another short piece to the battery positive.
Run the ground from the 7 pin connector to a frame ground near the trailer battery, ground the original smaller trailer white wire here as well. and connect another heavy gauge wire from the frame ground to the battery negative.
Connect the remaining (yellow, green and brown) wires from the 4 pin to the 7 pin, in their appropriate places.
If my recaller is correct the positions are (while looking in the plug in the Jeep) at 1:00 12 volt hot, at 3:00 right turn/brake, at 5:00 ground at 7:00 signal from brake controller(if installed), at 9:00 left turn/brake, ant 11:00 is tail lights, and the center is usually labeled Aux and used sometimes for back up lights.
It is a good thing to always double check my remember and test on your rig.

[bobhenry]

PRETTY GOOD REMEMBERIN'

[wlooper89]

Karl,

I had a similar situation with a Jeep tow vehicle and Little Guy with 4-wire flat connector. The Jeep came with the 7-wire round plug and already had a battery charge wire. I converted the trailer to a seven wire round connector and hooked up the wires for charging the battery. It was not very difficult. I used the existing wires on the trailer for running lights. The color codes are different between 4 and 7 wire so that needs to be taken into account. I added this to the trailer replacing the flat 4 connector.
http://www.etrailer.com/pc-TEC~H20046.htm
A junction box like this is good for making the connections inside a water resistant enclosure. Ring connectors on the wire ends work well with this type J-box.
http://www.etrailer.com/p-38656.htm

Bill

[Karl]

Despite some great suggestions on how to do it myself, I decided to have the 7-pin connector professionally wired. Of course, being somewhat colorblind makes doing electrical wiring exciting unless I have someone else around to tell me what color a wire is ... so, for $34 of labor plus $6.95 for a 7-pole connector and $3.45 for a 30amp breaker, I got it all wired. $45.02 out the door (including tax) seemed like a very good deal.

In case anyone else in our group is within easy driving distance of the Metro-Detroit area and is looking for someone to perform work on their trailer such as electrical wiring, packing of bearings, welding of receivers onto the underside of their trailer (see "TD Manufacture Suggestion: 4 Receiver Tubes? Here's Why..." at (http://www.tnttt.com/viewtopic.php?t=30925&highlight=), please consider giving your business to:

Mike Forbes
Forbes Trailers
4902 Highland Road
Waterford, MI 48328
248-673-7876
http://www.forbestrailers.com/

Mike, the owner, loves to tinker so for any crazy ideas you have, he is probably willing to take the time to figure out how to get it done.

This was my first encounter with Mike but I feel good enough about him (and his work) that I plan on having him pack the trailer bearings next spring and take care of anything else that I can't do myself on my Little Guy.

[wlooper89]

Despite some great suggestions on how to do it myself, I decided to have the 7-pin connector professionally wired. Of course, being somewhat colorblind makes doing electrical wiring exciting unless I have someone else around to tell me what color a wire is ... so, for $34 of labor plus $6.95 for a 7-pole connector and $3.45 for a 30amp breaker, I got it all wired. have, he is probably willing to take the time to figure out how to get it done.

That sounds like a great deal. Getting under my Little Guy on a creeper was not that much fun. Based on your cost I was probably saving about $3 per hour for my time. Considering the cost of the cable and J-box I may have been working for free. Good thing this is a hobby.

Happy trails.

Bill