two batteries on one battery tender?

Discussion in 'Thumpers' started by Bigbird, Nov 22, 2004.

  1. Bigbird

    Bigbird "Dog Is My Co-Pilot"

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    Has anyone tried keeping two batteries charged using a single battery tender? I wondered if it's possible to connect 2 batteries to one battery tender and keep them both charged up thru the winter storage period? Could you hook the two up in series and then connect the battery tender to the first, and have it charge both? Or will I have to alternate tending from one to the other?
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  2. Chopperman

    Chopperman I am dead

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    For one thing, I am glad you asked first. Batteries seem benign, but have a volitile side that makes me jumpy when considering stuff like that. I dont know the answer to your question....just wanted to toss in a comment
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  3. AFekete

    AFekete Long timer

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  4. xtphreak

    xtphreak from B4 "adventure bikes"

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    read the article closely linked by Afekete

    it won't work in series.
    that would require a 24 volt charger, you are thinking about hooking them parallel ... (+ to +) & (- to -)

    if the charger will supply enuff current, hook charger to one battery, use 10 ga wire to connect to second ... again all + together & all - together
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  5. Frank Warner

    Frank Warner Traveller

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    The basic answer is NO.

    IF you connect in series then the voltages will add. And the batteries MUST be of the same capacity (amper hours CCA etc). If they are not th esame one battery will charge befoer the other causing the non charged bater to never get a full charge.


    IF you connect in paralell the voltages will be ok. But if one battery is faulty it can cause the second good battery not to get a charge and may well cause the good battery to fail too.

    Basicly - don't do it. Not usless you spend days balancing the batteries. In which case you may as well buy another battery tender! I use to ballance batteries for frequency standards. Never again - I'd just buy new ones.
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  6. SteveAZ

    SteveAZ Long timer

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    What he said. Just save the headache and get another float charger.


    You could float them in parallel *if* they are both already fully charged and topped off, but it just ain't a good idea...
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  7. GOAT BOY

    GOAT BOY GOAT BOY

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    NOOOOOOOOOOOOOOOOOOOOOOOOOOOOO! Don't do it you'll be sorry.

    GOAT BOY
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  8. Sa-tevo

    Sa-tevo Jetmechs' Winston Wolf

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    It will be difficult to do. Here's the problem:

    I used to help set up commercial slot car racing tracks. We often used lead acid truck batteries for the current capacity. If connected in parallel with no diodes, one battery would try to charge the other battery. This will lead to one weak cell in the low battery to run away and charge more, outgassing, getting very hot, and scaring the hell out of me as I didn't want a spark in that enviroment if I disconnected the charger or cables in the circuit. The batteries in parallel will always try to balance themselves, which they can never quite accomplish.
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  9. Bigbird

    Bigbird "Dog Is My Co-Pilot"

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    OK, I'll just get another battery tender. :nod Thought it was worth looking into, but obviously the "solution" is more trouble than the original problem is worth. Thanks to one and all for the feedback. Cheers :thumb

    BB
    #9