Batteries in Parallel

Discussion in 'OnBoard Electronics & Controls' started by seanform, Apr 26, 2008.

  1. seanform
    Joined: Jul 2007
    Posts: 10
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    Location: Malta

    seanform Junior Member

    Hello,
    I have a 21" boat with an inboard engine. I have 2 12v batteries which I connect in parallel (+ to + and - to -) to start my 12V self starter. I disconnect one battery only when I am not using the boat and it is in the sea thus I leave one battery only connected. Am I damaging the batteries?

    Thanks
     
  2. lazeyjack

    lazeyjack Guest

    nope they will both discharge at same rate abt .1 volt month
     
  3. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    Just make sure that they are charged together, it takes about 15 % longer to charge tahn it did to discharge, so be careful. Barreries are usually charged at abpoy 10 % of their amp/hour capacity, so if they were 200 amp/hours, you would be charging at about 20 amps.
     
  4. seanform
    Joined: Jul 2007
    Posts: 10
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    Location: Malta

    seanform Junior Member

    Thanks for your replies. What I do is that when I arrive on the boat I connect the other battery in parallel and start the engine with both batteries connected. I do not disconnect anything while cruising thus both batteries are being charged. -- Before I leave the boat when the engine is off I disconnect one battery and leave one connected.
     
  5. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    Why do you leave one connected, is it because of the bilge pumps, if not then disconnect both batteries. The bilge pumps should be wired outside of the main battery switch anyhow.
     
  6. seanform
    Joined: Jul 2007
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    Location: Malta

    seanform Junior Member

    Yes it is for bildge pumps as a safety precaution. I do not use switches as if they mulfunctiuon which I found out they sometimes do they have bad consequences. I just unscrew the battery fly nut of the bridge lead. Thanks again
     

  7. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    OK, no worries, you are doing the right thing.
     
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