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What is the 12 volt battery for?

Discussion in 'Gen 2 Prius Technical Discussion' started by toad, Jan 28, 2007.

  1. toad

    toad New Member

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    This may be a stupid question but why does the prius have a 12 volt battery rather then power everything from the traction battery? I understand the 12 volt battery powers the normal things (radio, headlights, etc.) but why can't you power this from the hybrid battery?

    Thanks.
     
    #1 toad, Jan 28, 2007
  2. Frank Hudon

    Frank Hudon Senior Member

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    <div class='quotetop'>QUOTE(toad @ Jan 27 2007, 09:18 PM) [snapback]381852[/snapback]</div>
    short answer is, it's used to boot the computer which closes the HV relay which then powers the car. Also the 12 volt is charged from the inverter so in reality it's charged from the HV battery.
     
    #2 Frank Hudon, Jan 28, 2007
  3. Orf

    Orf New Member

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    Written on my battery are words to the effect that it powers the brake system.
     
    #3 Orf, Jan 28, 2007
    1 person likes this.
  4. qbee42

    qbee42 My other car is a boat

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    In addition, having a separate 12V battery allows the traction battery to be completely disconnected when the car is shut down, preventing a costly total discharge in the event a door was left open or something like that. Furthermore, the inverter would have to run to power any 12V items, such as lights and the radio, unless you want to have purpose designed lighting and electronics, plus high voltage wiring running around the car.

    Tom
     
    #4 qbee42, Jan 28, 2007
  5. Frank Hudon

    Frank Hudon Senior Member

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    <div class='quotetop'>QUOTE(Orf @ Jan 27 2007, 10:12 PM) [snapback]381868[/snapback]</div>
    and the power steering
     
    #5 Frank Hudon, Jan 28, 2007
  6. Allannde

    Allannde Just a Senior

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    <div class='quotetop'>QUOTE(qbee42 @ Jan 28 2007, 08:04 AM) [snapback]381932[/snapback]</div>
    This is the real reason.

    If you ever have to replace the 12v battery, thank your lucky stars it wasn't the traction battery. Toyota engineers went to amazing lengths to protect the traction battery. We need to be grateful that they did.
     
    #6 Allannde, Jan 28, 2007
  7. duanelaugh

    duanelaugh New Member

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    <div class='quotetop'>QUOTE(Allannde @ Jan 28 2007, 01:39 PM) [snapback]381983[/snapback]</div>

    Excellent answer!!!!!!!!!!!!!!!!!!
     
    #7 duanelaugh, Jan 28, 2007
  8. toad

    toad New Member

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    Thanks everyone. :)

    All are very good points. I guess it would be very bad to have the traction battery completely drained.
     
    #8 toad, Jan 29, 2007
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