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Three Batteries in the Prius? Sorry bout the noob question..

Discussion in 'Gen 2 Prius Accessories & Modifications' started by darkpyro, Jun 22, 2005.

  1. darkpyro

    darkpyro New Member

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    So let me get this straight...there is a 12 volt battery in the engine compartment for starting the car, and there is a hidden battery I''ve come across in the trunk on the passenger side. What is this battery for, because I've heard the NiMH battery is located under the rear seats. If this is correct what is the purpose of the battery in the rear on the passenger side? Also what battery are you using to connect your amp? I plan on having my crossfire vr705d installed by the local car audio shop and I was wondering which battery I should have them connect it to. Obviously I wouldn't want to draw from the hybrid battery. Any constructive input is appreciated. Thanks.
     
    #1 darkpyro, Jun 22, 2005
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    2 batteries. The 12V is NOT in the engine compartment. It's located on the right side of the cargo area. The NiMH resides under the floor BEHIND the rear seats.
     
    #2 Tideland Prius, Jun 22, 2005
  3. Bill Merchant

    Bill Merchant absit invidia

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    Re: Three Batteries in the Prius? Sorry bout the noob questi

    [font=Comic Sans MS:7aa97061fe]Actually there are two batteries and a capacitor power source. There is no 12V battery in the engine compartment.

    If you want to see your batteries, got to the back of your Prius and take out the bin box over your spare tire and the cover on the right (passenger) side. The bare metal box in front of you is the HV battery (not under the rear seat, but behind it). The small battery in the right corner is the 12V battery you'd have to draw power from. Pretty puny...

    The capacitor power bank is for emergency braking, don't even think about tapping it.[/font:7aa97061fe]
     
    #3 Bill Merchant, Jun 22, 2005
  4. darkpyro

    darkpyro New Member

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    Re: Three Batteries in the Prius? Sorry bout the noob questi

    I guess I was just OWNED. lol...thanks for the quick reply. Also is there any real benifit to changing the puny 12 volt battery to an optima yellow top or something?
    Also, what is under the positive/negative cover in the engine compartment?
     
    #4 darkpyro, Jun 22, 2005
  5. Bill Merchant

    Bill Merchant absit invidia

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    Re: Three Batteries in the Prius? Sorry bout the noob questi

    <div class='quotetop'>QUOTE(darkpyro\";p=\"100600)</div>
    [font=Comic Sans MS:81bcf5e03a]Some people have discussed bigger battery reserves to power big amps. I don't know about sound systems like that, so I can't really respond.

    Where do you see a positive/negative cover in the engine compartment? Don't play with any of the orange wires, those are high voltage.

    It just occurred to me, are we talking about an '04+ Prius?[/font:81bcf5e03a]
     
    #5 Bill Merchant, Jun 22, 2005
  6. jayman

    jayman Senior Member

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    Re: Three Batteries in the Prius? Sorry bout the noob questi

    Another point to keep in mind is that there is NO conventional starter/alternator in the Prius. The Motor/Generator is used to start the engine, and the M/G is used to provide power to the HV battery.

    The red cover under the hood has fuses and is also the emergency boost point to use in case the 12 vdc battery should happen to go dead. Even if the HV battery pack is fully charged, if the 12 vdc battery is dead, the car is dead.

    The inverter/converter is used to properly charge the 12 vdc battery. Yes, it's tiny, think lawn garden tractor battery.

    All the 12 vdc battery has to worry about is "booting" the car when you press Start, running the electric brake boost pump, the lighting, the electric cooling pump for the engine thermos, audio system, cabin HVAC blower.

    Even the variable speed electric air conditioner compressor is run off the HV system
     
    #6 jayman, Jun 22, 2005
  7. efusco

    efusco Moderator Emeritus
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    Changing out the 12v would be both difficult and potentially dangerous. The one in Prius is a sealed unit b/c there's no place for fumes/gasses to exhaust to.

    A larger capacity 12v would offer only the advantage of being able to sit with your headlights on longer or to sit listening to music or something longer.

    Very little energy is required to get the Prius into "READY" mode. The 12v boots the ECU and opens the circuit with the HV battery which allows the ICE to start and the car to 'go'.
     
    #7 efusco, Jun 22, 2005
  8. darkpyro

    darkpyro New Member

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    Re: Three Batteries in the Prius? Sorry bout the noob questi

    Well Bill, I don't plan on tapping into 500 or so volts anytime soon. I would have figured out that there wasn't a battery in the engine compartment if I cared to disasemble the prius, or poke around a bit more. By the way, my prius is a 2005 and the battery I would potentially replace it with is a maintenance free Optima battery that is sealed. I don't believe this would produce any of the dangers you speak of about replacing it with a conventional battery. Can anyone confirm this?
     
    #8 darkpyro, Jun 22, 2005
  9. rocco

    rocco Member

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    Good to know what battery is where. Since I seem to be hitting the bottom of my car while going over curbs, etc.
     
    #9 rocco, Jun 23, 2005
  10. ymmv

    ymmv New Member

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    You might want to look at Odyssey -- their batteries have better specs (power, weight) than the Optima products. In my humble. But I'm not sure these cells would be any better than the factory unit unless you just want more beef.
     
    #10 ymmv, Jun 23, 2005
  11. ScubaX

    ScubaX Member

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    Re: Three Batteries in the Prius? Sorry bout the noob questi

    They are sealed in that they are maintenance free. But they must still vent. Venting only occurs though during some extreme conditions. I read a recent post here that claims that Optima batteries do come in versions with vent tubes. They have some batteries that are similar sized to the Prius and if they have vent tubes, you could probably replace it directly.
     
    #11 ScubaX, Jun 23, 2005
  12. dzitlow

    dzitlow New Member

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    Re: Three Batteries in the Prius? Sorry bout the noob questi

    Any information about life expectancy/replacement frequency of the 12 volt auxiliary battery in the Prius? What are costs of replacement 12 battery? Can replacement be bought "off-the-shelf" at an auto parts supply store or place like Wal-Mart? :D
     
    #12 dzitlow, Jun 23, 2005
  13. Bill Merchant

    Bill Merchant absit invidia

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    Re: Three Batteries in the Prius? Sorry bout the noob questi

    [font=Comic Sans MS:8381aa58ee] It was Evan Fusco who mentioned venting issues, so I can't confirm or deny. My thought is that if you install high wattage amps and huge speaker systems, you had better not turn off the HSD while they are running unless you want to drain the miniscule "computer-boot" battery. And, as JayMan said, if the 12V is dead, the car is dead, no matter what charge level the HV battery has.[/font:8381aa58ee]
     
    #13 Bill Merchant, Jun 23, 2005
  14. DanMan32

    DanMan32 Senior Member

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    Though it is a standard 12V battery, it is sealed but vented. That is the critical criteria you should follow. Oh yes, and the posts are not standard diameter.

    You probably could rig something else up and retrofit, but keep fluid and gas safety in mind.
     
    #14 DanMan32, Jun 24, 2005
  15. DanMan32

    DanMan32 Senior Member

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    Yes, the + is under the red cap in the black fuse box. The negative terminal could be any unpainted chassis or block area.
     
    #15 DanMan32, Jun 24, 2005
  16. jtmhog

    jtmhog Member

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    About 4-5 months ago there was a post where the battery was replaced with a different battery. Check the records. It detailed changing the connectors and hold-down bracket.
     
    #16 jtmhog, Jun 24, 2005
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