Charging battery with tow vehicle

Golden_HVAC wrote:
The 7 pin has really small wires, perhaps #12, but likely smaller #14. And you need the ground wire to handle not only the battery charge 20 amps, but also the brakes 15- 18 amps, and all the running light amps as well.

Not true at all - standard recommended wire gauge for 7-pin Bargman connector.

My buddy upgraded his wiring to #8 wire, and reported that his trailer battery will now fill up while towing from one location to another as long as he drives about 3 hours or a little more.

But because he wanted to stay put longer at a lakeside campground, he ended up buying a small generator and charges the battery with it. A solar panel probably would be a better idea.

If you install a pair of 120 - 150 watt panels on the RV roof, you should not have a problem with arriving with low batteries. SunElec.oom had 140 watt solar panels for $229 a few months ago. THey are 12 volt nominal (21 open circuit - what you want) and aluminum frames for attaching to the RV.

There are less expensive per watt panels without frames, but you don't want that one.

Some say to run a larger cord along with the factory 7 pin wiring. By installing a #10 wire, and a special plug, such as 277 volt angled plug (so your brother in law does not plug it into house power because it fits and blows up a battery). This connection is larger and can carry 25 amps with minimal voltage drop.

The 7 pin has really small wires, perhaps #12, but likely smaller #14. And you need the ground wire to handle not only the battery charge 20 amps, but also the brakes 15- 18 amps, and all the running light amps as well. Sure some of the ground amperage might be carried through the hitch to the truck frame.

If you buy some #10-3 wire from Home Depot, and run it from the battery to the truckbed, to a plug there, then #8 wire from the alternator to the relay that will shut off when the engine is off, then to the plug at the back of the truck, you will have maximum voltage to that plug while driving.

Good luck,

Fred.

marquette wrote:
I didn't want to hijack the current thread on time e to charge a battery with the tow vehicle but I read of people changing the charging wire to a larger size to get better charging. For those that have done it how large of a wire size did you go to and how much effect did it have? I have a 2001 Suburban and know I have 12v to the center pin on the 7 pin but no idea beyond that of what I have.

Think not only about the vehicle side, but also Elkhart uses the cheapest wire they could between the trailer 7way and the batteries.

I'd recommend looking at a minimum of 4ga wire straight off the alternator, through an isolator or solenoid, all the way to the trailer batteries. Through a fuse in there somewhere too.

No I haven't done this but studied it in close detail. Instead of dealing with low voltage fickle DC, I ran an extension cord that allows me to run my small Yamaha generator in the truck bed and power the trailers charger directly.

marquette wrote:
I have a 2001 Suburban and know I have 12v to the center pin on the 7 pin but no idea beyond that of what I have.

Centre pin on a 7-pin Bargman is an auxiliary, often used for back up lights when the vehicle is in reverse, Pin 4 is the charge line.