Battery Question from todays CarTalk..

Discussion in 'The Garage' started by ThorRex, Feb 8, 2014.

  1. ThorRex

    ThorRex Been here awhile

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    Heard this on CarTalk today, as I'm a NPR nut these days….guy has a boat that ran fine all day…starting and stopping engine throughout the day. Ties boat up that evening, comes back the next day and realizes he left lights on and battery is totally dead….0.0 vdc…marina removes battery and charges it in the shop. re-installs battery.Tries to start engine but starter motor runs, but the clutch on the shaft doesn't engage the starter gear to flywheel.Test starter on bench, starter engages fine, reinstall in boat, starter spins, but no clutch….I've never heard of this, it seems marina guy reversed polarity on the totally dead battery and it took the charge backwards thereby turning the starter backwards as well. Installed new battery and all was well. Anyone else ever heard of this being done? Is it even possible??
    #1
  2. H96669

    H96669 A proud pragmatist.

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    The answer is yes to reversing the polarity on a dead battery. Lucky guy, he didn't fry any electronics.:eek1

    There is a thread on here where someone got a brand new battery with polarity reversed for his bike. I think that fried something.:eek1

    8 more minutes....I'll listen to it.:clap
    #2
  3. Anorak

    Anorak Woolf Barnato

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    Yes. I saw it happen once. A customer did it. His car ran fine but the ammeter showed a discharge when he drove it.
    #3
  4. trailer Rails

    trailer Rails Long timer

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    I seem to remember a car that was produced where the cassis was positive. Like a MG or something.
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  5. PunkinHead

    PunkinHead Moobless Adventurer

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    One of my first cars was a '66 Beetle with a 6V positive ground system.
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  6. eric1514

    eric1514 (R)

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    6V yes, positive ground, no.

    Wiring Diagram
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  7. Wansfel

    Wansfel 50 yrs on 2 wheels

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    Older generators could flip polarity also.
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  8. PunkinHead

    PunkinHead Moobless Adventurer

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    I'm relying on fuzzy 20+ year old memories here but I swear the positive battery post was tied to chassis on mine. It wouldn't surprise me if the previous owner somehow managed to reverse it and I, as a dumb teenager, just didn't know any better. I got the car for free - it'd sat a decade or so in a field after the owner's son ran it into a tree. The owner said if I could get it out of the field I could have it. My father had a buddy that built VW based dune buggies who gave me a spare torsion bar front end. I put a really nice Imron paint job on it (shot in the garage without a mask because, again, I was a dumbass teenager) and I ended up making quite a profit on it.
    #8
  9. H96669

    H96669 A proud pragmatist.

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    I think you are right about the VW positive ground. I am a little fuzzy on that also. And fuzzy on my Austin I don't even remember the built year of that POS but I am pretty sure that one was also positive ground 12V.

    And so a quick Google search led me to believe again for both VWs and Austins. And plenty of British cars were like that. Not many of them where I was growing up and doing service calls/jumpstarts in them cold winter mornings but still something we had to be aware of.:wink:
    #9
  10. ThorRex

    ThorRex Been here awhile

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    Yeah, I remember some cars were Positive grounded systems way back when, but I guess a totally dead battery can be recharged with reversed connections/polarity and it'll take the charge….interesting..
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  11. concours

    concours WFO for 41 years

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    This. The Brits had positive earth on cars and bikes.:D
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  12. OldPete

    OldPete Be aware

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    Generators can be polarized. Youtube it if interested.
    Yes, lead acid batteries can get reversed. I've seen it happen.

    Not sure if it's true but positive earth/ground was thought to reduce corrosion.

    If desired, starter rotation can be reversed by re-drilling and turning the brush plate end 90 degrees.

    Note: Never make-up an electrical connection dry. A Q-tip wipe of WD40 is better than nothing.
    #12
  13. Anorak

    Anorak Woolf Barnato

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    Americans too. My 1951 Mercury was 6v positive ground.
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  14. wcohl

    wcohl Been here awhile

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    My son did this on his vehicle. After two days of trouble shooting and swapping out electrical parts from a similar donor vehicle, wit no luck, that car never ran again.
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  15. H96669

    H96669 A proud pragmatist.

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    My newish charger does recognize polarity and won't charge if it is reversed. Now I am wondering what would happen with a 0v battery. I'll go try that, I am sure I can find a dead battery under the snow somewhere.:eek1

    Car talk...:clap I guess the reversed battery was the answer to last week's puzzler.I should have listened to that one and for once have the answer. This week's puzzler is on reversing switches just so you don't get thrown to the gators....:rofl

    Starters spinning in reverse....got some BMW K-bikes riders that one. Mark the covers when dismantling. Too easy to turn them 180 degrees and apparently have the starter spin in reverse.There is a heck of a funny thread on that on some Cadillac forum, they sure liked to chuck s...t at each others over the "possibility vs impossibility" of such things.:rofl
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  16. OldPete

    OldPete Be aware

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    2 brush starters(most bikes) 180 degrees... 4 brush starters(most cars) 90 degrees to reverse rotation.:deal
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  17. Motopsychoman

    Motopsychoman Not a total poseur

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    Yes, you can reverse charge a lead-acid chemistry. But, it will not have any capacity whatsoever. The battery is toast. It will self-discharge very rapidly.

    Also, any battery that has been run to 0.0 volts is toast. Safe discharge levels for lead-acid chemistry is around 70% to 75% of float voltage. For a typical 12V battery that is about 10.5 volts (75% of 13.7V).

    Batteries that are designed for deep discharge can be run down lower, but most are only rated to about 55%.

    AGMs are more durable than flooded (wet-cell) batteries, but shouldn't routinely be run down below 70%. At 10.5V, there is very little capacity left in the battery.
    #17
  18. Motomantra

    Motomantra Registered Lurker

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    ''66 was the first year for 12v, 1300cc, & it was also the first year they dropped the dual link front end.
    If my foggy memory is correct.
    #18
  19. eric1514

    eric1514 (R)

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    66 was the only year of the 1300. It was still 6v. 12 volt happened in 67.

    Scroll down to the middle of THIS PAGE if you don't wanna believe me.
    #19
  20. concours

    concours WFO for 41 years

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    I had a '66 I cut up for a dune buggy. 6V, I remember my bud EXPLODING the battery jumping it with a 12 truck (running!! 13.6V!!) and the front end was the standard twin horizontal beams with torsional leaves. It was a 1300. Sure of that, after I blew it up, and had to buy cyls, pistons, head, etc:lol3:1drink
    #20