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Charging boat trailer battery off 7 pin

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Mulely

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So, my 3500 has dual alternators and my boat trailer has a battery that runs the wash down tank pump and potentially later on a winch and/or power jacks. Can I just tap into the 12v circuit and use that to charge the battery while i drive? I'd put a circuit breaker on it to protect the trucks system.
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The trailer should already be wired to pull 12V from the 7-pin and charge the battery, unless the battery you are talking about is wired independently of the emergency brake battery.
 
Yea of course you can thats how it should be setup just run a 30A fuse on the battery positive lead on the trailer
 
AH64ID said:
The trailer should already be wired to pull 12V from the 7-pin and charge the battery, unless the battery you are talking about is wired independently of the emergency brake battery.
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Yeah, it's going to be separate of the brake battery that had the 12v line to it.

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Mulely said:
Yeah, it's going to be separate of the brake battery that had the 12v line to it.

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I would either tie them together, or simply make the brake battery the battery that powers the accessories. You won’t have to modify any wiring this way and the truck will charge it.

If you need a bigger battery than what is there for the brakes then upgrade it.

There isn’t a real good reason to have two separate 12V systems on a trailer.

If you need more charging capacity than the 7-pin a separate circuit for a DC-DC charger is the way to go.
 
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I would remove the brake battery completely and just setup with one good deep cycle battery for everything. If you find the battery is not charging fast enough you can do a DC/DC charger or just run # 1 wire from the truck batteries to the rear bumper with an Anderson plug then a mating connector on the trailer to the batteries (thats what i do with my winch on my flat deck which i also have a set of booster cables setup to plug in to the same connector.
 
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