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Audi: Correct battery voltage?

  1. #1
    Fred
    Guest

    Correct battery voltage?

    I fitted a new Exide battery to my 98 A6 2.5 TDI in March (correct spec
    BTW).

    The problem is that before I start the engine in the morning the voltmeter
    shows the voltage as just over 10v. Once the car is started (a struggle
    sometimes in cold weather) the voltmeter shows about 13v. If I stop the
    engine and go back after an hour or so the voltage shows over 12v.

    My feeling is that the battery is not holding the charge as it should, but
    on both occasions that I have taken the battery back to the shop I bought it
    at, it tests OK (well it would as I have just driven there). The alternator
    test shows it is charging OK.

    I would appreciate some feedback on what batteries should show on the
    voltmeter before starting, after being left overnight.

    TIA



  2. #2
    Chris
    Guest

    Re: Correct battery voltage?

    Fred wrote:
     

    With the engine off, the battery should read at 12 to 12.5 volts. With
    the engine running, it should read between 13.75 and 14.25 volts. Based
    on your description, it sounds like you have a bad battery.

    Cheers,

    C



  3. #3
    Tony
    Guest

    Re: Correct battery voltage?


    "Chris Mauritz" <net> wrote in message
    news:V9VJb.32634$srv.hcvlny.cv.net... 
    voltmeter 
    but 
    bought it 
    alternator 

    Before you change the battery, you may check to see if you have a short and
    a drain on the battery. This becomes more obvious after an overnight rest.

    With engine shutdown check the current used; if it's excessive (not sure how
    much, but say over 1 amp; ask a tech. on this), then start taking electric
    fuses out until you find the culprit circuit and go from there.

    Cheers,

    Tony



  4. #4
    daytripper
    Guest

    Re: Correct battery voltage?

    On Sun, 4 Jan 2004 12:13:14 -0500, "Tony" <net> wrote: 

    If there's an amp of current being drawn from the battery when the car is
    supposedly totally "off", there's something wrong.

    With the car turned off, no lights on, no doors open, etc - I mean good and
    truly "off", the only devices that should be drawing any power are the clock,
    the "memory" logic within the audio system head, and the alarm system.
    Between those the current should be well under 100 milliamps.

    And a 12v battery reading 10v at rest is likely fatally damaged if not just
    plain dead...

    /daytripper
    '00 s4 6spd

  5. #5
    dave
    Guest

    Re: Correct battery voltage?

    >From: "Fred" com 


    Yes 10 volts does not sound too positive. lol
    You need to make sure that the connections are very clean and tight at the
    battery, grounding cables from the battery, and also at the alternator.
    Sometimes if the connections are not clean and tight you will lose voltage.
    You can check this with your handheld voltmeter. Start testing voltage at the
    battery terminals, then check the battery clamps, then hold the positive lead
    from the voltmeter on the battery and touch the negative lead to the body of
    the car. Compare results! If they are the same, you can test them with the
    engine running. Then do the same type of test with the alternator, but the
    engine has to be running. It is a little harder with your vehicle, but it is
    doable if you make the connections BEFORE running engine. You are looking for
    a drop in voltage which might mean too much resistance (not good). Then clean
    any areas where you note this drop.
    This is all assuming that the battery is good.
    I just gained an extra volt when I cleaned the grounding spots on my
    alternator. Hey that is like free power!! <g>

    Others have told you to check for a drain too. That should be done first!

    Good luck and let us know!

    later,
    dave
    Reminder........
    Before you criticize someone, you should walk a mile in their shoes. That way,
    when you criticize them, you are a mile away from them, and you have their
    shoes. Frieda Norris


  6. #6
    Fred
    Guest

    Re: Correct battery voltage?

    many thanks for all your suggestions guys - much appreciated !


    "dave" <comANTISPAM> wrote in message
    news:aol.com... 
    voltmeter 
    but 
    it 
    alternator 
    voltage. 
    the 
    lead 
    of 
    the 
    the 
    is 
    for 
    clean 
    way, 




 

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