Charging boat batteries using truck's alternator.

Discussion in 'Boats, Blinds, & Gadgets Forum' started by smashdn, Jan 3, 2018.

  1. smashdn

    smashdn Elite Refuge Member

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    So this is done with rv's apparently. My grandfather had his boat hooked up this way as well and my dad is continually after me to do this. Read between the lines in my thread about the cover and you can guess why.

    Anybody that has done it, what do I need? I think the round seven blade trailer connectors have a "hot" output already. I just need to harness it and put it to the batteries some way (fused, relayed, etc) so I don't blue anything up or catch it on fire.

    TIA
     
  2. stevena198301

    stevena198301 Elite Refuge Member Supporting Member

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    7-pins have two different wiring diagrams. One puts an "AUX" in the center pin, one puts a brake controller pin there. Depending on how your trailers 7-pin is wired, you'll need to run wires back to the battery area from that center or outside pin (I can't remember off the top of my head which outside pin is for AUX). Should be easy enough. And your alternator should be able to keep up just fine.
     
  3. blkduck

    blkduck Senior Refuge Member

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    this is wiring on my suburban, the aux was actually the backup lights and what i used to add led backup lights in the bumper. on diagrams the 12v charging is sometimes referred to as the 12v hot. you can normally just look at the wire colors on your harness and see what they are. the colors should be standard (trailer brakes are blue, etc..)
    [​IMG]
     
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  4. Rubberhead

    Rubberhead Elite Refuge Member

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    I did it using the 30A trailer braking circuit in my Explorer.

    I already had a trolling motor plug on the battery and a trolling motor socket in the boat so I just installed a trolling motor socket of the same size near the passenger side floor in my Explorer. I simply set the battery on the floor board and plugged it in. Most of my duck hunts are 30 or more minutes from the house so it always keep the battery charged properly.

    [​IMG]
     
  5. smashdn

    smashdn Elite Refuge Member

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    I don't want to pull the batteries out of the boat but the trolling motor socket has given me an idea. I have a tm socket right up on the front deck. I bet I can rig it up with a tm plug right there and charge batteries that way.
     
  6. tcc

    tcc Elite Refuge Member

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    You're gonna want a solenoid or an auxiliary battery system, not just a hot wire, to do it right. If not your boat batteries will drain the truck battery when the ignition is off.
     
  7. stevena198301

    stevena198301 Elite Refuge Member Supporting Member

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    I'd just make sure it's at least fused independently. If you already have a TM plug up front, you should be able to unhook your TM, and put a charging plug in it's place while you drive (I could be wrong in this part, but I don't think so). Most TM plugs just tie directly back to the batteries.
     
  8. smashdn

    smashdn Elite Refuge Member

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    My tm plug is direct back to batteries, no fuse.
     
  9. Pot Hole

    Pot Hole Elite Refuge Member Sponsor

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    Absolutely. My TM circuit has a 50 amp inline (resettable) fuse.
     

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