battery cranking voltage drop?

Discussion in 'The Garage' started by scapegoat, Apr 6, 2012.

  1. scapegoat

    scapegoat Pushin forward back

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    I have a FXDXT that has a OEM AGM in it thats now 5 years old. If it sits for a few days and I take a read just cranking it over the voltage reads 9.5+ -. Voltage after several days of sitting reads about 12.5 12.6. Info Ive read says voltage a couple days after a full charge or ride should still be 12.8. Ive never had a battery stay that far up on voltage that I can recall. Que pasa?
    #1
  2. Swinerider

    Swinerider n00b

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    Any twelve volt battery should be 12.6 fully charged, more would be unusual, sounds like your battery is just weak (5 years old is an eternity for any motorcycle battery!!!) or you have a heavy draw. I recently had a problem starting even with a new lithium battery eventually found the starter wire right on the starter was a little loose and corroded causing a very high draw when cranking.Replace the battery first, its on its last leg!
    #2
  3. H96669

    H96669 A proud pragmatist.

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    12.6 that's about right for most AGMs, but all depends on the manufacturer. 12.74 and above is 100% SOC for an Odissey.

    Best battery info out there, charge tables are in there and they do say for AGMs to check with the manufacturer as to what the voltage should be at 100% SOC.

    http://www.batteryfaq.org/

    Only way you'll know if your battery is any good is with a load test.:1drink
    #3
  4. GreaseMonkey

    GreaseMonkey Preshrunk & Cottony

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    Do you have trouble with it starting after sitting for a while? Does it have any parasitic draw?

    If you are not going to use it for a couple weeks sometime, take a reading and then leave the battery disconnected for that time and see what the state of charge is when you get back. Also, washing the battery with soap and water would be a good idea if you have a concern with it losing a charge.
    #4
  5. erkmania

    erkmania Still Adventuring

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    10.2 volts is about the minimum you want while cranking. It sounds like your battery is on its way out.
    #5
  6. OldPete

    OldPete Be aware

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    Replace the battery and go for heavyer gage battery cables.
    Big twins benefit from cable up-grade.
    #6
  7. Gray_Rider

    Gray_Rider Been here awhile

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    +1000 - general rule is if it drops below 10V at cranking, it is time to replace it.
    #7
  8. scapegoat

    scapegoat Pushin forward back

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    Well that solves that one. Thanks Guys :D
    #8