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Excessive Drain- Traction Battery

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Priusaurus110, Sep 29, 2010.

  1. Priusaurus110

    Priusaurus110 Junior Member

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    Hi All:
    My Car: 2005 Prius, 54,000 mi, located in Colorado, driven every day on flat terrain and gentle hills

    My Problem: For 5 years perfomance on routine driving has been very consistent-- traction battery always stayed between 1 and 3 bars down (green and high blue). Rather suddenly, the car shows the following on every trip: starts in mid-blue battery range, within a mile or two drops all the way down to 1 or 2 bars (purple) and will stay there for the entire trip whether it is 5 miles or 20 miles.

    My search of these symptoms on the forum indicated aux battery may be the problem. Last week I swapped out the original battery for a new Optima Yellow-Top. The symptoms did not go away.

    No other symptoms or warning lights. I don't have a ScanGauge so I don't know if it is throwing any codes that are not triggering a warning light.

    Car goes in to the dealer in 2 days. Any suggestions?

    Thanks
     
    #1 Priusaurus110, Sep 29, 2010
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, I have a few:

    1) Your lack of a ScanGauge is not detrimental. Usually you cannot count on that instrument to show any DTC besides those logged by the engine ECU. If that ECU had logged any DTC then you would expect the check engine light to come on.

    2) You will probably have to pay for one hour of labor time when you take the car to the dealer. Since you don't have any warning lights on, it is highly unlikely that any problems will be found and you will be out ~$100.

    3) Since CO has no shortage of steep mountains, I think you should stress the traction battery by driving up Pikes Peak as fast as you can. Or if you are removed from that area, find a similar stressful drive in your locale, drive it as fast as local law and safety permits, and see what happens. Good luck.
     
    #2 Patrick Wong, Sep 29, 2010
  3. seilerts

    seilerts Battery Curmudgeon

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    If you take it to a dealer, or an independent shop with Techstream or AugoEnginuity, they can do a test where they track the highest and lowest module voltages in the traction battery. The difference should be less than 200 mV or so all the way down to 1 bar. That's about the only test I know of that can indicate HV battery health in the absence of codes. If there was a code you would get the red triangle. They can also measure the current delivered by the HV battery when the car is idle (Ready, ICE off, A/C off, lights off, accessories off). It should be in the neighborhood of 1 amp. They can also measure current regen as well with a road test, and should see up to 100 amps.

    Have you noticed any changes in fuel economy?
     
    #3 seilerts, Sep 29, 2010
  4. Priusaurus110

    Priusaurus110 Junior Member

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    Thank you Patrick and Sielerts:
    Yes, there has been a noticable decrease in mileage when this started from hi40s/low50s to now a consistent 40-41 MPG. This is good info to have as I take it in for troubleshooting.
     
    #4 Priusaurus110, Sep 30, 2010
  5. JimN

    JimN Let the games begin!

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    Have you checked the 12v battery's voltages on the MFD? Just because a battery is new doesn't mean it is good. My new Toyota battery lasted ~6 weeks before being replaced under warranty.
     
    #5 JimN, Sep 30, 2010
  6. Priusaurus110

    Priusaurus110 Junior Member

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    Update:
    As Patrick predicted, taking in the car with no error light would result in a "can't find anything wrong" result.

    I appreciate the recommendation to specifically ask the dealer for the high voltage battery check, because it is not one of their "standard" diagnostic tests, and even with my symptoms, they weren't going to perform it until I asked for it.

    The results were within specs: lowest module voltage was 15.05 V and highest was 15.19 V. All module internal resistances were 0.19 or 0.20 ohms

    DTC: none detected

    So, it was worth the $100 to me for the piece of mind that the HV battery was healthy. But I still have the mystery on my hands of why I started operating in the "purple" zone after so many years...

    Oh, and I did test the newly installed Optima battery-- checks good
     
    #6 Priusaurus110, Oct 12, 2010
  7. Ken S

    Ken S Member

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    Your problem sounds similar to what I'm seeing with my 05 with about 48,000 miles. I have a feeling the HV battery is starting to go bad and it is causing a decline in fuel mileage (mine is down to mid 30s after averaging in the mid 40s.



     
    #7 Ken S, Oct 12, 2010
  8. seilerts

    seilerts Battery Curmudgeon

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    Just FYI, internal resistance values should be around 0.02 ohm. Are you sure it is 0.2?
     
    #8 seilerts, Oct 15, 2010
  9. Priusaurus110

    Priusaurus110 Junior Member

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    You are correct: the diagnostic report does show 0.019 and 0.020.

    Sorry for going rogue on the decimal point! Good catch...thanks.
     
    #9 Priusaurus110, Oct 17, 2010
  10. Flaninacupboard

    Flaninacupboard Senior Member

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    Have you tried force charging it? (sit in P and press the accelerator, it will charge without moving.) That should get you up to all 8 bars, then go for a drive and see what happens.
     
    #10 Flaninacupboard, Oct 17, 2010
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