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2004 Prius Alternator ?

Discussion in 'Gen 2 Prius Technical Discussion' started by dakao, Jun 11, 2011.

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  1. dakao

    dakao New Member

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    Is there an alternator to charge the 12V battery for 2004 Prius?
    I just replaced my 12V battery but when the car is turned on with AC running and I measure the 12V battery it is reading only 11.98V but when the car is turned off 12V battery is 12.45V
    It doesn't seem right to me. Can anyone explain please???
    What charging the 12V battery or what is bad? My 12V battery is brand new just bought from Toyota. Thanks
     
    #1 dakao, Jun 11, 2011
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The 201 volt Traction battery charges the 12 volt battery via an inverter. Mine reads 13,8 volts when Ready.
     
    #2 JimboPalmer, Jun 11, 2011
  3. tomlouie

    tomlouie Member

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    Try measuring with car in Ready with AC off.
     
    #3 tomlouie, Jun 11, 2011
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The A/C compressor is also run off the 201 volt HV Battery, so it should not impact the 12 battery much. (Same reason, we do not want to run the engine JUST to have A/C or electricity)
     
    #4 JimboPalmer, Jun 11, 2011
  5. dakao

    dakao New Member

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    OK! without starting the car the battery measured 12.45V and read 12.18V when car started without A/C running and no radio either.
    Must be something wrong with the charging system ??
    Thanks
     
    #5 dakao, Jun 11, 2011
  6. seilerts

    seilerts Battery Curmudgeon

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    How are you measuring the voltage? At the terminals with a voltmeter? Are all connections tight, i.e. the two terminals and the where the negative attaches to the rear fender well?
     
    #6 seilerts, Jun 11, 2011
  7. dakao

    dakao New Member

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    Yes I measure the voltage at the battery terminals and everything is good and tight. Brand new battery and it sucks too no one else sells but Toyota dealers.
    I think there is something wrong...
     
    #7 dakao, Jun 11, 2011
  8. bisco

    bisco cookie crumbler

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    you can get an optima battery, but i would go back to the dealer and ask them to test it. could just be a bad battery.
     
    #8 bisco, Jun 11, 2011
  9. dakao

    dakao New Member

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    Too late to get the optima and dealer won't take the battery back once the box is opened.
    Anyway, anyone knows what could be the problems beside the battery??
    Thanks
     
    #9 dakao, Jun 11, 2011
  10. bisco

    bisco cookie crumbler

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    see jim's post #2. could be an inverter problem?
     
    #10 bisco, Jun 11, 2011
  11. dakao

    dakao New Member

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    Jim's post #2 ?? Whaere can I find his posts?
    Thanx
     
    #11 dakao, Jun 11, 2011
  12. seilerts

    seilerts Battery Curmudgeon

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    The gist is that the DC converter inside the inverter may not be working. When the car is in Ready, voltage at the battery terminals should be 13.7V-14.4V. Only in IG-ON would a reading less than 12V be normal. I do think it is possible to get that particular portion of the inverter repaired, but it may be cheaper to get another inverter from a junkyard, approximately $500. Toyota dealer would naturally insist that you spend $4000 to have a new one installed.
     
    #12 seilerts, Jun 11, 2011
  13. bisco

    bisco cookie crumbler

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    sorry, jimbo's post. #2 is after your first post which is post #1. but seilerts has you covered in his post just before this one. however, i would still go back to the dealer first and make sure you didn't get a defective battery.
     
    #13 bisco, Jun 11, 2011
  14. efusco

    efusco Moderator Emeritus
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    Also, a new DC-DC inverter should not be that expensive, though a salvage will, of course, be much less. We're not talking about the big Inverters under the hood for the motor-generators.
     
    #14 efusco, Jun 11, 2011
  15. seilerts

    seilerts Battery Curmudgeon

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    Also see this for pictures of a bad 12V dc/dc converter: Inverter mechanical

    It may take a trip to the dealer to confirm a bad dc/dc converter inside the inverter assembly, since there are no trouble codes.
     
    #15 seilerts, Jun 11, 2011
  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    What does "started" mean? Do you mean the Prius is READY, or do you mean the Prius is IG-ON where all the dashboard warning lights are on?

    If READY, then your car has a problem, most likely a failed DC/DC converter which means the inverter will have to be replaced.

    If IG-ON, the voltage reading is normal but you should not operate the car for any length of time in that condition because the 12V battery will quickly discharge.
     
    #16 Patrick Wong, Jun 11, 2011
  17. dakao

    dakao New Member

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    I have no idea what you mean by READY. All I know is when I get in the car, step on the brake and push on the Power button that when the battery goes down to 12.18V. Will that put the car in Ready mode ??
    What is IG-ON ? I have no idea either.
    BTW, when I drove the car today with the A/C on after 10 miles the ABS and Brake lights came on so I turned off the AC and those lights went off.
    Where is the DC-DC inverter located at?
    Thanks all your guys helps.
     
    #17 dakao, Jun 11, 2011
  18. efusco

    efusco Moderator Emeritus
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    If you step on the brake and push the power button the car will go into "Ready" - there's a light on the dash that says "Ready" which is why we call it that.

    If you get in the car while it's off and push the power button once without stepping on the brake you go into Accessory mode, if you give a second push still without stepping on the brake you're in Ignition On mode.

    It certainly sounds like there's a problem if you're seeing the ABS and brake light. You need to have the dealer check the vehicle and see if they can pull any codes, but it's looking more and more like it's your DC-DC inverter.
     
    #18 efusco, Jun 11, 2011
  19. dakao

    dakao New Member

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    Thank you for explaining.
    So where is the DC-DC inverter?
     
    #19 dakao, Jun 11, 2011
  20. efusco

    efusco Moderator Emeritus
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    Not sure, hoping Patrick will come back and answer that. It may be under the hood with the other inverters, but don't hold me to that.

    I found the following:
    Circuits for the dc/dc converter share space on the same circuit board that is believed to house the A/C compressor inverter, and TO-packaged devices are again bolted to the cooling plate of the overall ICU assembly.
    Special Issue: Inside the Toyota Prius: Part 5 - Inverter/converter is Prius' power broker
     
    #20 efusco, Jun 11, 2011
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