7 pin trailer plug for charging boat batteries?

[Hanr3]

My truck came from teh factory with a 7 pin trailer connector. One of hte pins is to charge RV batteries.

Anybody hook up their boat batteries to this pin? If so, what will it take to make it work? DO I need some sort of charge controller or does the truck already control the charge to teh RV batteries like it does for the truck battery?

 

[Wallijig]

I believe it's just fused up under hood. I have hooked into that wire for topper lights and aux power in toppers. One should add a battery isolator or dual output alternator for charging. Without one of those one would be in parallel with truck battery. You can get them at a high end car audio dealer.
I have installed both. I liked putting in dual output alternator better. Just look in alternator application book for vehicle you have and order replacement. Unbolt and rebolt back in hookuping using same factory plugs. then just have separate post on it for charging aux batteries isolated from truck electrical system.

 

[Hanr3]

Not sure I follow. It is on a seperate fuse, 30 amp, which I have to install when I hook up the wire under the hood. Everything I looked at shows it is intended to recharge batteries in an RV. Based on the fact that it is a 10gauge wire Im assuming its not a quick charge, say less than an hour, but rather a longer charge, couple hours for a dead battery.

What Im not sure about is how RV charge their batteries off teh 7 pin plug. Do they have a seperate charger which draws power off that pin?

Dual alternator sounds great, however Im almost positive my truck came with a high output alternator. The truck came from the factory with the 7 pin connector prewired, receiver hitch, auxilary tranny cooler, and the wiring under the dash for a brake controller. To make all 7 pins work all I need to do is hook up that red battery wire under the hood, and install the brake controller. Towing capacity is about 6,000 pounds, not bad for a midsized SUV. Too bad GM stopped making them. I'm new to this 7 pin plug thing and still havent been able to find anything ont eh trailer end, specifically related to teh battery charging.

 

[Bugpac]

I don't believe it is intended to charge the batterys, It is intended to maintain a trailer brake battery, and power a few 12 volt lights. Charging large rv or boat batteries if they are real weak is really gonna tax the stock alternator. They wont last long that way. With a dc circuit, you could run a wire from your tail light and it will charge the battery, Just sayin! Seven blade plug is simple, all its adding is brake wire, backup lights, and the 12 volt positive.

 

[Wallijig]

A dual out put alternator is different then a high output alternator. The dual out put alternator is more to isolate you 2 electrical systems. If think alternator is big enough I would hook that wire to battery isolator. It would keep batteries from drawing off each other.
Here's link to dual output alternator. it has isolator incorporated in it:
https://compare.ebay.com/like/160408265261?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar


Here's link to isolator like I used man times:
https://www.autosportcatalog.com/warn-electrical-charging-and-starting/warn-dual-battery-isolators.cfm?mgsku=pp12160&sc=57513&sc=57513&mr:trackingCode=6DEC17FC-890D-E111-804A-A8C6AF702B72&mr:referralID=NA&origin=pla&mr:adType=pla&mr:ad=16085190886&mr:keyword={keyword}&gclid=CNe9ysy4h7ECFW35tgodzFmgIg