marine batterys with your starting battery

Discussion in 'Boat Modification Journal' started by crackers, Jun 22, 2009.

  1. crackers

    crackers New Member

    Messages:
    296
    State:
    Arkansas
    If i run a 12,14ga wire from the positive side of my starting battery to my trolling motor battery and put a large diode in line with that wire it should charge my trolling battery while the engine is running and the diode should isolate the two batterys from each other, and use a common ground too both batterys. has any one done this. (after all a diode is an electronic one way valve) if i do this im going to put a fuse in line with the diode for safety at the starting battery....will this work
     
  2. cantstopgrandma

    cantstopgrandma New Member

    Messages:
    955
    State:
    MD
    If my thinking is right, with such a settup, your trolling motor will be using both batteries while it is running. It might be hard to find a diode that has the amperage capacity to basically take half the amperage load of the trolling motor. A battery cutoff switch will take care of that problem, but you gotta remember to isolate your TM battery before using the TM. You should probably also make sure your starting battery is a daul purpose, not just a starting battery, as it will be drained and recharged just like a deep cycle.

    Maybe someone else can confirm/deny all of this. I'm going on 2 electronics classes from high school, and its been a few years.
     

  3. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    You can buy onboard charging systems that will charge your your batteries from the outboard.
    The larger question is what is the output amperage of the outboard and would you really gain anything out of it rather then just stepping up to larger amp hour batteries.
    Are you going to be running the outboard long enough to benefit the batteries?

    I've always preferred to charge my deep cycles slow.
     
  4. crackers

    crackers New Member

    Messages:
    296
    State:
    Arkansas
    Both of you ppls answers are some thing I never thought about, Im going to try it still and see if it works but will put an electronic relay in line with my trolling motor and when I power it on it will cut out the charging line from the other starting battery. Ill use a large diode and put it on a heat sink. They make some pretty heafty diodes.