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Question about the 12 Volt Battery

Discussion in 'Prius v Technical Discussion' started by M8s, Nov 17, 2011.

  1. M8s

    M8s Retired and Lovin' It

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    I've read a lot of posts where people have allowed the little 12 volt battery to get discharged somehow and shortened its life.

    I assume the Prius vee is the same as other Prii in that the traction battery keeps the 12 volt battery charged. There is no alternator tasked with charging the 12 volt, just the two MGs that charge the Traction Battery.

    If that's correct, then why does it hurt the 12 volt battery to (e.g.) leave a light on? How can it run down the 12 volt battery and damage it but not hurt the traction battery?
     
    #1 M8s, Nov 17, 2011
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The Traction battery is only energized when the car is in Ready mode.Most damage happens when the car is off.
     
    #2 JimboPalmer, Nov 17, 2011
  3. M8s

    M8s Retired and Lovin' It

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    I see, the traction battery goes off-line but the 12 volt remains on-line. So, if I had left an interior light on all night (and I'm not saying that I did), that wouldn't be as forgivable as I'd hoped.

    Thanks Jimbo
     
    #3 M8s, Nov 17, 2011
  4. 2sk21

    2sk21 Member

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    Is there a link to some information about what exactly is powered by the 12v battery? I know from reading the description of the Hybrid Synergy Drive that the MG1 is responsible for starting the ICE.
     
    #4 2sk21, Nov 18, 2011
  5. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    There are very few items NOT powered by the 12 volt system. The air conditioning compressor, MG1, MG2, and the inverter are powered by high voltage. So far as I know, everything else is 12 volts.
     
    #5 JimboPalmer, Nov 18, 2011
  6. qbee42

    qbee42 My other car is a boat

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    How about the PTC heaters?

    Tom
     
    #6 qbee42, Nov 18, 2011
  7. DetPrius

    DetPrius Active Member

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    I still haven't figured out the requirements for the PTC heaters to be activated. Single digit tempts, full HV battery, max heat demand both auto and manual, cold soaked ICE, and I've only had them come on once. I knew they were on due to the smell and cabin heat being produced with an ice cold ICE. They are a great idea, but I wish I knew how to activate them at will.
     
    #7 DetPrius, Nov 18, 2011
  8. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    qbee I am living in MS, I forgot one ever heats one's car.
     
    #8 JimboPalmer, Nov 18, 2011
    1 person likes this.
  9. ken1784

    ken1784 SuperMID designer

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    PTC heaters are fused by 40A from the 12V line.

    Ken@Japan
     
    #9 ken1784, Nov 18, 2011
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  10. Danny Hamilton

    Danny Hamilton Active Member

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    Yes, there are relays that open when the car is shut off. These relays physically disconnect the high voltage battery from the rest of the car. When you try to turn the car back on, it uses the power from the 12V battery to close the relays to reconnect the high voltage battery. If you don't have enough power left in the 12V battery, then the car can't close the relays and therefore can't draw any power from the high voltage.
     
    #10 Danny Hamilton, Nov 18, 2011
  11. M8s

    M8s Retired and Lovin' It

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    Great explanation. Thanks!
     
    #11 M8s, Nov 26, 2011
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