Dual batteries w/marine switch, not working, only charging 1 battery, HELP!

Discussion in 'The Garage' started by dawson444, Jan 29, 2003.

  1. dawson444

    dawson444 1/2 ton status

    Jul 5, 2000
    Likes Received:
    Raleigh, NC
    Ok, I have a dual battery setup w/ a marine battery switch, here is it [​IMG]

    Here is my problem:
    The alt. doesn't seem to be charging battery 1

    with the truck running and switch on ALL
    bat. 2 shows like 14v, and 12 V on bat. 1

    w/ truck running and switch on battery 2
    same as switch on all, 14V @ bat. 2, 12V @ bat 1

    w/ truck running and switch on battery 1
    12V at both batteries

    w/ switch in off position
    (haven't tried it)

    Why is this happening? My guess it has something to do w/ the fact that all the wiring for the truck is still hooked up to battery 1. I haven't moved any of the wires for the rest of the truck, they are all still hooked up to the starter. I'm not sure though. Thanks for any help!
  2. bigblock454

    bigblock454 Clack Clack Clack Premium Member

    Jun 18, 2002
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    Terre Haute IN
    I would say the switch is bad.
  3. txbartman

    txbartman 1/2 ton status

    Jun 1, 2001
    Likes Received:
    Plano, TX
    I used a simple solenoid-switch combo on mine and have never had this problem. I am not familiar with the 'common' setting on the marine switch.

    All your wiring still on bat #1 should not affect anything when the batteries are connected. When the circuits are all connected, it is one big pool like have one battery. Electrical current will not flow from only one battery, it will flow from both (or the alternator) whichever is easiest (path of least resistance). First thing I would check is your grounds. Each battery must ground to the same common grounding feature as the alternator. If one of your batteries is not properly grounded, it will never take a charge nor will it contribute current. When you measure voltage drop across the battery, don't measure between the posts. Measure between the positive connection at the switch and a common ground point (chassis, engine block, alternator casing, whatever). If you have a bad ground, one of your batteries should read 0V.

    To see if it is your switch, try a few things...

    1. Connect another wire from your alternator to bat #1. When running and switch in #1 or #2 position, it should only be charging #1. When in All, it should be charging both (all the circuits are connected). If this does not charge #2 when in all, then your switch is not letting current flow through to #2.

    2. Do the same thing as above, only connect the alternator to #2. In the same manner, battery #2 should be the only one charged in the #1 or #2 position and both should get a charge under the All setting.

    3. Try removing the switch from the equation. Connect bat #1 and batter #2 POS to POS and NEGs to ground . Then connect one of the batteries (doesn't matter which) to the alternator. This is the same as having your switch in the All position. If this doesn't work, you have serious issues.

    Roughly, here is how mine is set up. The solenoid is controlled by a switch either connecting or disconnecting the setup.

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