[Question] Dual battery issue
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Dual battery issue

  1. #1
    Senior Member Itsahobby's Avatar
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    Default Dual battery issue

    Hi all,
    I'm having an issue with my dual battery setup. #2 battery voltage drops to 2.5 volts at the terminal block when the ignition key is in the on position.

    Here is what I have:
    Guest Battery switch set to #1, voltage at the output of the switch 12.7 volts. Turn the ignition to the on position, measure the voltage at the ignition terminal it's 12.7 volt.
    Guest Battery switch set to #2, voltage at the output of the switch 12.7 volts. Turn the ignition to the on position, measure the voltage at the ignition terminal its 2.5 volts. Nothing works. Motor wont start, gauges don't come on.

    The output of the switch goes to the starter then to the terminal block.

    Just doesn't make since to me. The terminal at the starter is the common terminal for the battery switch output, the all 12V goes out from there.

    Any thoughts on where I should look?
    Thanks,
    Jerry

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  3. #2
    Senior Member Itsahobby's Avatar
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    Default Still checking

    Update,
    Double check the output when on #2 and it is 2.5 at the feed of the battery switch.
    Swapped batteries and I still see 2.5.
    Could it be the battery switch? I check the ohms and they are the same at position 1 as they are on position 2.
    Seems like I have a voltage drain when using battery 2, but it just not make since to me.


    Quote Originally Posted by Itsahobby View Post
    Hi all,
    I'm having an issue with my dual battery setup. #2 battery voltage drops to 2.5 volts at the terminal block when the ignition key is in the on position.

    Here is what I have:
    Guest Battery switch set to #1, voltage at the output of the switch 12.7 volts. Turn the ignition to the on position, measure the voltage at the ignition terminal it's 12.7 volt.
    Guest Battery switch set to #2, voltage at the output of the switch 12.7 volts. Turn the ignition to the on position, measure the voltage at the ignition terminal its 2.5 volts. Nothing works. Motor wont start, gauges don't come on.

    The output of the switch goes to the starter then to the terminal block.

    Just doesn't make since to me. The terminal at the starter is the common terminal for the battery switch output, the all 12V goes out from there.

    Any thoughts on where I should look?
    Thanks,
    Jerry

  4. #3
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    Default Battery Switch Problem

    Quote Originally Posted by Itsahobby View Post
    Update,
    Double check the output when on #2 and it is 2.5 at the feed of the battery switch.
    Swapped batteries and I still see 2.5.
    Could it be the battery switch? I check the ohms and they are the same at position 1 as they are on position 2.
    Seems like I have a voltage drain when using battery 2, but it just not make since to me.
    It sounds like you have a voltage drop across the selector switch.
    If you have a voltmeter, use it to check the voltage drop across your selector switch. You should see just a few tenths at most voltage drop across any switch. Try your readings from the Feed terminal to position #1 and then from the feed terminal to position # 2 (Use the low reading scale)
    In both tests put the positive lead on the "feed" terminal and the negative lead on the output terminal.
    An ohm meter will not help you see a voltage drop. Hope this helps. If you don't see your problem at the selector switch, just keep moving your negative lead toward the ignition feed until you spot the drop.

    Note: The voltage drop will only occur and be seen with a closed circuit and current flow.
    Hope this helps with your situation.
    Last edited by Maxey; 08-06-2016 at 05:13 PM.

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  6. #4
    Senior Member Itsahobby's Avatar
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    Default

    Thanks,
    I did this and #1 shows 12.7 volts, #2 shows 2.5 volts. This just seems to be extreme, I went ahead and ordered a new battery switch.
    Thanks so much for your help.
    --Jerry

    Quote Originally Posted by Maxey View Post
    It sounds like you have a voltage drop across the selector switch.
    If you have a voltmeter, use it to check the voltage drop across your selector switch. You should see just a few tenths at most voltage drop across any switch. Try your readings from the Feed terminal to position #1 and then from the feed terminal to position # 2 (Use the low reading scale)
    In both tests put the positive lead on the "feed" terminal and the negative lead on the output terminal.
    An ohm meter will not help you see a voltage drop. Hope this helps. If you don't see your problem at the selector switch, just keep moving your negative lead toward the ignition feed until you spot the drop.

    Note: The voltage drop will only occur and be seen with a closed circuit and current flow.
    Hope this helps with your situation.

  7. #5
    Senior Member ol guy's Avatar
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    Default

    Quote Originally Posted by Itsahobby View Post
    Thanks,
    I did this and #1 shows 12.7 volts, #2 shows 2.5 volts. This just seems to be extreme, I went ahead and ordered a new battery switch.
    Thanks so much for your help.
    --Jerry
    Have you had a load test done on the batteries and how old are they? Sounds like #2 has a dead cell. M

  8. #6
    Senior Member Itsahobby's Avatar
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    Default

    Quote Originally Posted by ol guy View Post
    Have you had a load test done on the batteries and how old are they? Sounds like #2 has a dead cell. M
    Nope, haven't done a load test but I swapped #1 and #2 and still see the same issue.
    I've always had trouble starting on #2, makes me think the switch may have been faulty from the beginning.
    Will see when I install a new switch.
    Right now my back is killing me after lifting those batteries in and out. LOL
    Thanks
    Jerry

    Sent from my SAMSUNG-SM-G900A using Tapatalk

  9. #7
    Just Me snoc653's Avatar
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    Default

    Quote Originally Posted by Itsahobby View Post
    Nope, haven't done a load test but I swapped #1 and #2 and still see the same issue.
    I've always had trouble starting on #2, makes me think the switch may have been faulty from the beginning.
    Will see when I install a new switch.
    Right now my back is killing me after lifting those batteries in and out. LOL
    Thanks
    Jerry

    Sent from my SAMSUNG-SM-G900A using Tapatalk
    You ruled out the batteries but what about the cables? Try using jumper cables and connect the no.2 battery neg to the no.1 battery negative. It won't rquire heavy lifting. You did confirm that the switch terminal from the no.2 pos has the right voltage didn't you? If it doesn't just use the jumper cable and run it to the switch from the no.2 pos.
    So many projects, so little time

  10. #8
    Senior Member LiquidDan's Avatar
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    Default

    Everyone has ideas and I will add mine....
    Load test each battery post to post first...then include the cable...that will tell you if it is the Perko Switch or a cable
    Just my .02 cents
    Originally Posted by gn7 "Stick to making the worlds best engine stand."

  11. #9
    Senior Member Itsahobby's Avatar
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    Thanks guys,
    I'll give these a try in the next day or so. My back is bad enough I can't climb in and out of the boat, but it is getting better.
    Thanks again for all the suggestions.
    --Jerry
    Last edited by Itsahobby; 08-08-2016 at 09:19 AM.

  12. #10
    Senior Member propless's Avatar
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    Default

    And check the ground for that #2 battery.

  13. #11
    Senior Member Itsahobby's Avatar
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    Default We have a winner!

    That was it!
    I'm really surprised, and realize that should be the first thing to check, but this boat has 0 corrosion and I looked at the ground cables, they looked good.
    I connected a jumper from the ground of the battery to the block, bingo, everything works.
    I removed the ground cable and noticed that the contacts have aluminum coating on them. I sanded that off and hooked it back up and everything is working fine.
    Thank you all for the suggestions, I really appreciate it.
    --Jerry

    Quote Originally Posted by propless View Post
    And check the ground for that #2 battery.

  14. #12
    Senior Member propless's Avatar
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