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I just ordered my 2016 36CKTS 5th wheel and am now looking for a truck to pull it. I am considering F-350 or Ram 3500 dually. The salesman asked if I wanted a second alternator. He did not know, and I don't know if when I am traveling down the road the truck charges the 5th wheel batteries, and if so do I need the second alternator for that?

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Welcome to the Escapee's forums. We are here to help so don't hesitate to join in.


Very rarely is there any reason for a second alternator even though the standard connections for most RVs to the tow vehicle do include a line to charge the RV battery(s). There are many discussions of RV electrical problems on these forums and you may want a high output alternator if one is available but very unlikely that you would have a need for two of them. The main issue to be studying is the weight limitations of the tow truck and trailer.

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...He did not know, and I don't know if when I am traveling down the road the truck charges the 5th wheel batteries..,

The standard 7-pin RV wiring harness, does include a hot wire that can supply power to the RV and charge the battery. It may or may not be connected if the harness is installed at the factory. It may be necessary to connect the hot wire (often red) to a post on the truck's power center and possibly insert a fuse in the fuse box. The hot wire in a standard RV harness is often no larger than 10 guage and depending on the length of the wire run from the truck to the RV batteries and the size of the battery bank may not provide that good or fast a charge.


Depending on what 12V loads you have running in the trailer, the charge from the truck may not even keep up with the power being drawn. After 4-5 hours on the road, with just the normal phantom loads and the refrigerator on propane; the smart charger on my trailer will start to charge at 20-30 amps (12v) as soon as shore power is connected. If you are planning on having a residential refrigerator in the RV and leave it running while travelling, I seriously doubt that the standard harness wiring will be sufficient. There have been a number of discussions on this and other RV forums regarding increasing the capability to charge the RV battery bank from the tow vehicle.

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