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Unexpected Auxillary Battery Discharge Problem

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by WXWISE, Feb 15, 2010.

  1. WXWISE

    WXWISE Junior Member

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    Ok, So I've been having this issue with my auxillary battery discharging for no apparent reason. I first experienced this last Summer after I drove over a large bump too fast, and that large bump hit the middle underside of the vehicle pretty hard. This bump was in my grandparents driveway. So then I parked my car and returned only 30 minutes later to leave again, and the car was completely dead. Total freakout, The battery was fully discharged. Eventually I figured out how to jump start it and then after that everything was fine. That is up until tonight. After working a 10-11 hour shift at work. I must not have hit the brake when I pressed start, as it went into auxillary mode. Noticed the car had very little power, as everything was dim, and I got that red triangle of death. I depressed the brake again and pressed start and the car started up fine, with full power. I drove the 10 miles it took me to get home with no problems. Got home. turned the car off. Tried to see if I was still haveing the same issue. Again in auxillary mode, the battery was only putting out about 6 Vlts, and still getting the red triangle, but still able to power on the car. Anyway I'm going to get it looked at by my dealer tommorow, and I'll probably have to have it jumped in the morning. So this all brings me to my question to everyone, as to what could be causing this battery discharge. Nothing was left on in the car when I left it, I'm sure of it. Any ideas would be appreciated.

    Thanks
     
    #1 WXWISE, Feb 15, 2010
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Have you replaced the 12V auxiliary battery recently or is it original equipment? If the latter, then it is ~5 years old, and I suggest you replace it now.
     
    #2 Patrick Wong, Feb 15, 2010
  3. WXWISE

    WXWISE Junior Member

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    It's the original battery. I will probably need to replace it, but What I don't understand is why it would be working perfectly fine earlier in the day and then failure, for no reason that I can think of.
     
    #3 WXWISE, Feb 15, 2010
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Well, from your first post it sounds like the battery has been marginal since this past summer. The combination of cold winter weather and a marginal battery condition to begin with apparently resulted in the battery finally failing tonight.

    If you can replace the 12V battery yourself then you'll save the dealer service dept. labor charge. Some owners have been charged $250-$300+ for the replacement battery + labor. If you DIY you'll just have to buy the battery, which should cost ~$130 or so from the dealer's parts counter.
     
    #4 Patrick Wong, Feb 15, 2010
  5. dogfriend

    dogfriend Human - Animal Hybrid

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    If you are down to 6v, you probably have more than one cell that is damaged (dead).
     
    #5 dogfriend, Feb 15, 2010
  6. WXWISE

    WXWISE Junior Member

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    I'm curious to know if the Auxillary battery is considered a "Hybrid-Related Component"? Just wondering if I could get the battery replaced under the "Hybrid-Related Component Coverage" warranty? Just noticed that the 12-Volt Auxiliary Battery is listed under the "Prius Hybrid System" chapter of the Bentley Prius Repair manual. I mean 5 years seems like a short lifespan for a 12-Volt battery...don't you think?
     
    #6 WXWISE, Feb 15, 2010
  7. dogfriend

    dogfriend Human - Animal Hybrid

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    No. I'm pretty sure the 12V battery falls under the 3yr/36k warranty.

    5 years is actually pretty good for a 12V battery in my experience. I have had one or two last longer than that on other vehicles, but many fail much sooner. It is also related to the environment where the battery is used (really hot or really cold weather kills batteries sooner).
     
    #7 dogfriend, Feb 16, 2010
  8. WXWISE

    WXWISE Junior Member

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    Thanks for all the expertise, Dogfirend and Patrick Wong.
     
    #8 WXWISE, Feb 16, 2010
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