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Battery Problem or is it...

Discussion in 'Technical Q&A' started by enjoythemusic, Aug 11, 2005.

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  1. enjoythemusic

    enjoythemusic F1 World Champ

    Apr 20, 2002
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    Steven
    #1 enjoythemusic, Aug 11, 2005
    Ok, have been having a weird charging problem. It seems that over 4k rpm the battery light comes on. Ok, probably a bad alternator electronics. But here is where i have a question. The car does seem to charge the battery so...

    Decided today to swap out batteries from an Interstate for a race battery (Enersys PC680) and it reads 12.9V (full charge) when the ground is not attached. The moment i attach the ground cable the voltage goes down to 7V. i have good ground continuity and do not have an electrical short according to my meter.

    And the problem is???
     
  2. WaltP

    WaltP Formula 3

    Nov 1, 2003
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    Walt P
    #2 WaltP, Aug 11, 2005
    Have you or can you put an amp meter in line to see if there is something pulling down the voltage.
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    Steve Magnusson
    #3 Steve Magnusson, Aug 11, 2005
    Steve -- Can you remeasure:

    top of "+" battery post (not the female terminal) -to- top of "-" battery post (not the female terminal) = ?V

    top of "-" battery post -to- (metal) chassis ground = ?V

    If you were/are drawing enough amperage to pull a healthy 12.6V battery down to 7V, the connection spark would be a thunder-clap and your cables would vaporize ;)
     
  4. enjoythemusic

    enjoythemusic F1 World Champ

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    Steven
    #4 enjoythemusic, Aug 11, 2005
    12.9V not hooked up, about 7V when i have ground hooked up.



    Alas, not sure as i gave up and uninstalled the damn thing. i did have continuity all the way to the chassis ground including before and after the ground lift plug that resides under the front of the 308 (drivers side).



    :) It was immediate and not a delay to the lower voltage when i would hook up ground. What i mean is WITHOUT ground terminal ON THE CAR ITSELF by the drivers side it read 12.9V. The moment i put the grounds together the voltage immediately dropped.

    i removed the Enersys battery and put back the 'stock' Interstate and it is fine. Voltages all measure fine, etc. My meter only goes up to 20A and at the 20A setting it reads only 0.25. WTF?????


    ADDED: Called them with my fidning and it may be a cracked plate that only shows up under load. ARGH! A wasted few hours and i have to pay to send this 15 lbs thing back to them for testing.
     
  5. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
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    #5 No Doubt, Aug 11, 2005
    Bad battery! Doh!
     
  6. thecarreaper

    thecarreaper F1 World Champ
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    Sep 30, 2003
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    Savannah
    #6 thecarreaper, Aug 11, 2005
    Steve, take it to a auto parts store and have it load tested to see what it does. may help settle your mind and save you more hassle. my battery died in my new truck saturday, at lunch WITH MY BOSS WITH ME ! i walked to walmart and bought a battery, a jump box and a meter. :)


    the factory nissan battery would read 12.85v sitting and would zero out under load. no lights, no horn ect. it too has a broken plate in it.

    must be the heat
    :) !
     
  7. CarlH

    CarlH Karting

    Feb 5, 2004
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    Carl H.
    #7 CarlH, Aug 13, 2005
    Steve,
    Shorted plates under load is a common battery problem. If something in the car was loading a good battery to the 7 volt range, you would find it quickly due to the smoke and burning wires.
     

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