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12V Battery Stats: Should I Replace?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Aaron, Jul 14, 2011.

  1. Aaron

    Aaron Member

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    Got the following voltage data. The car has been sitting for approx 18 hours:

    12.3 - accessory mode (nothing on)
    11.7- lights on
    11.4- rear window heater on
    11.1- lights & rear window heater on together

    Was reading the voltage should be between 12.6 and 11.9, so at 12.3 I guess I'm doing OK. Right?:confused:
     
    #1 Aaron, Jul 14, 2011
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  2. jdenenberg

    jdenenberg EE Professor

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    It's not in terrible shape. Did you drive short trips or long ones before your Prius sat idle? If short trips, then your 12v just is not fully charged. If long trips, keep an eye on the battery as it is showing some weakness.

    JeffD
     
    #2 jdenenberg, Jul 14, 2011
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  3. Aaron

    Aaron Member

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    I just got back from a 330 mile trip without stopping.

    Will charging my cellphone while driving shorten the life of the 12V?
     
    #3 Aaron, Jul 14, 2011
  4. jdenenberg

    jdenenberg EE Professor

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    So just keep an eye on the battery.
    No, the charging system can supply up to about 100 amps for accessories without problems (except for a drop in MPG to supply the energy, about 1 MPG lost for each 10 amp of current load).

    JeffD
     
    #4 jdenenberg, Jul 14, 2011
  5. jdcollins5

    jdcollins5 Senior Member

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    Quick question, where did you measure the voltage? If by chance you read this on the screen in Service Mode, I would recommend reading it with a DVM right at the battery terminals or at least on the jump terminals in the engine fuse box. I read a difference of -0.7V on the Service Screen versus with a DVM right at the battery terminals.
     
    #5 jdcollins5, Jul 14, 2011
  6. Aaron

    Aaron Member

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    I read it in Service Mode and on my ScanGauge.
     
    #6 Aaron, Jul 14, 2011
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  7. dureel

    dureel New Member

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    How do you get voltage data? (sorry for being such a newb)
     
    #7 dureel, Aug 9, 2011
  8. F8L

    F8L Protecting Habitat & AG Lands

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    The best way is to have the vehicle shut down for 6+hours then use a digital volt meter to measure voltage at the battery terminals.
     
    #8 F8L, Aug 9, 2011
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