Running a charge wire

[Barbara Gardin]

I know this has been covered before but I am not good at searching and can't find it. We would like to run a simple charge wire to charge the trailer battery from our car battery while driving. Need a lesson on how to do this. We have separate 12volt and 120 systems

[Frederick L. Simson]

You usually run a 10 gauge (or larger) wire from the Tow vehicle's Battery Positive post thru isolation diodes to the 7-Pin connector's 12 volt pin.

Then you make sure you run a similar wire from the Trailer's 7-pin connector's 12 volt pin to the House battery positive post.

Link to "The 12 Volt Side of Life"

[Casita Greg]

I guess the first question to ask would be: Do you have a round 7-pin "Bargman" type trailer plug? To run a charging circuit you will need one if you don't already have one installed.

Wiring Code 7 way Car End # Color Gauge Circuit Function connector interior
1 white 10 ga. common ground
2 blue 12 ga. electric brake
3 green 14 ga. tail/running lights
4 black 10 ga. battery charge (+)
5 red 14 ga. left turn/stop
6 brown 14 ga. right turn/stop
7 yellow 14 ga. auxiliary/back up
Note on pin #7: Please note that the center terminal is labeled as an auxiliary circuit, most commonly used for backup lights, and is not a ground terminal as many try to make it.


Wiring Code 7 way Trailer End # Color Gauge Circuit Function connector interior
1 white 10 ga. common ground
2 blue 12 ga. electric brake
3 green 14 ga. tail/running lights
4 black 10 ga. battery charge (+)
5 red 14 ga. left turn/stop
6 brown 14 ga. right turn/stop
7 yellow 14 ga. auxiliary/back up
Note on pin #7: Please note that the center terminal is labeled as an auxiliary circuit, most commonly used for backup lights, and is not a ground terminal as many try to make it.

This chart should be used as a general guide only, you should always test before connecting your wiring.

This chart also may not be accurate for vehicles with factory installed trailer harnesses. In past 2-3 years manufacturers have begun to match the wire colors to the code for the common 7 way RV connector.

As a precaution, if your vehicle is equipped with a diagnostic indicator that tells you when a lamp is burned out or not functioning, you may need special wiring adapters and testers. Not using these adapters may cause damage to the vehicle wiring or computer.

In addition to the above some cars and trucks have a separate light for the brake light, most commonly identified by amber turn lenses in the rear. If you have this type of wiring a converter is required.

I recommend attaching the trailer harness ground directly to the frame or a solidly attached sheet metal part, using a screw or bolt. The single most common cause of trailer lighting problems is a poor ground on the tow vehicle or trailer.
the terminal.

Hope this helps.

[Phill Roehrs]

A 10 gage wire to the positive post is what I did, rigging it through my 7 pin as mentioned. On the advice of my submariner neighbor, who is way smarter about electricity than me, I added an in-line 20 amp fuse. If your camper battery happens to be drawn way down when you connect to the tow vehicle, the two batteries will try to equalize, quickly, drawing too many amps from to TV, which could be a problem, especially if the TV isn't started when you drain that many amps.

My fuse blew once, after a 5 day stay in the woods.

I also have a four-way isolator switch in the camper: off, camper only, TV only, and "both" camper and TV for the tow to charge. What I normally do, after blowing the fuse that once, is to keep the camper isolated from the TV (camper only) until I am hooked up and ready to tow. Then, while connected and the car running, I switch to the TV only setting to confirm I've got a good connection and a solid fuse, then I switch to "both" and give it a few seconds, then I switch back to TV only to check that the fuse didn't blow, then switch back to "both" for the tow and charge. Got the switch at a local marine shop, around $30.

I also, sometimes, run my 3-way fridge on DC during tow. But I do this carefully. I do what I described above, confirm connection and solid fuse, then I start the fridge on DC, give it a few minutes, and check again for solid fuse before I get on the road. If I've passed the start-up amp spike without blowing the fuse, I'm reasonably confident that the ice cream won't melt in transit.

[Matt in SV]

Do you know a good spot to buy a harness already wired up with six or eight feet of cable and the 7-pin connector? I figure I need to get from the tow vehicle socket to an interconnect at my trailer.

Regards,

Matt

[Bruce Thomas]

some uhauls had a 6 plug connecter instead of a 7.....i dont knw that the adapter you can but from napa allows a charge wire through there or now....I know i bought the adapter for mine and everything worked for the move home but didnt bother checking for that....id say the 7th may be for brakes? not sure ...........Bruce

[Michael Pupeza]

Barbara;
Be aware that, while the Charge Line will effectively charge the battery on trips, it is NOT a good idea to be running a lot of load in the trailer at the time, such as a fridge. Unfortunately, my installer used No. 12 wire for that line and it can't supply more than 7 Amps, while my fridge uses 18Amps - a loss of 11 Amps from the batteries while travelling. Otherwise, it does the job.
Mike

I know this has been covered before but I am not good at searching and can't find it. We would like to run a simple charge wire to charge the trailer battery from our car battery while driving. Need a lesson on how to do this. We have separate 12volt and 120 systems

[Perry J]

Do you know a good spot to buy a harness already wired up with six or eight feet of cable and the 7-pin connector? I figure I need to get from the tow vehicle socket to an interconnect at my trailer.

Regards,

Matt

Item #620146-1006 at NorthernTool.com is what you need and it's only $19.99. I've bought 2 of them for different trailers I have refurbished.
Northern tool is a great place to buy hardware for trailers.
I live in the Central Valley of California and their prices including shipping are usually less than I can buy locally.
I have bought trailer brakes, trailer jacks,molded connectors and a sway control and everything has been first class. Their customer service is great and they have fast delivery.
John

[Kevin K]

http://www.northerntool.com/shop/tools/pro...issearch=620146