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Hybrid Battery losing charge quickly

Discussion in 'Gen 2 Prius Main Forum' started by way0utwest, Jun 16, 2010.

  1. way0utwest

    way0utwest New Member

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    I have a 07 Gen II Prius with 64k miles on it. It's been great, but recently I changed tires to some new Bridgestones. They look slightly larger, and I am guessing they are a little heavier. After they were on, with warm weather in Denver, I got a tank of gas averaging 50mpg.

    However the last week it appears that the hybrid battery is both loosing charge quickly, and at times, gaining it quickly. I don't have exact figures, but my driving is about the same style/distance/speed it's been for 3 years, but when I park the car overnight, I wake up with purple bars (2) on the charge. As I drive, it can get back to full blue bars, but it seems to fall back down quickly, and run with 2 purple bars much more than I've seen it in 3 years.

    Any ideas? Is my hybrid battery dying early for some reason? Go for warranty check?
     
    #1 way0utwest, Jun 16, 2010
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Many of those symptoms are those of a 12v battery that has failed such that the HV battery is trying to charge it continuously, thus running down the HV battery.

    Like most cars, the 12 battery in a Prius lasts about 4 years. Unlike most cars the starter does not make slow grindy noises in a Prius which may be the normal way you tell if a 12 volt battery is low.

    Try this, once you car has sat a while turn it on Acc (no foot on the brake) and check how fast the power windows are, now start it and check again. If the windows are slower before the car starts, really have the 12v battery checked.

    12 Volt (12v) Toyota Prius Auxilary Battery for 2004, 2005, 2006, 2007, 2008, 2009 and 2010 with installation kit
     
    #2 JimboPalmer, Jun 16, 2010
  3. desertrider2215

    desertrider2215 Member

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    I have noticed in my 04 with almost 130xxx on it that my battery falls very quickly sometimes right when I start it up, and then it gains back fast (only sometimes it goes back up fast). Took it to the dealer since they are warrantied here in cal for 150,000 and they said it sounded like symptoms of a bad battery but ended up doing a flash on my software or something like that and updated it. It is still doing it so I am going to take it in this week or the next, hopefully they'll replace my battery this time because my MPG has been below 40 for quite a few months now. good luck.

    EDIT: getting a new 12V for mine (which I did) didn't solve the problem.
     
    #3 desertrider2215, Jun 16, 2010
  4. Bob64

    Bob64 Sapphire of the Blue Sky

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    The part about parking your car with the HV battery in the blue, 2 bars from the top, and waking up with 2 purple bar can be a sign of a dying battery...

    Test the 12v battery the real way, with either the mfd diagnostic screen or with a multimeter.
     
    #4 Bob64, Jun 16, 2010
  5. chuckknight

    chuckknight New Member

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    A dying HV battery, or a dying 12V battery?
     
    #5 chuckknight, Jun 17, 2010
  6. way0utwest

    way0utwest New Member

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    Thanks for the advice. I'll start with a 12V test and go from there.
     
    #6 way0utwest, Jun 17, 2010
  7. way0utwest

    way0utwest New Member

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    I used this procedure to test the battery:

    Get your Prius into "Accessory Mode" - Press the power button without touching the brake pedal.
    Put the MFD into "Maintenance Mode" - Press and hold the "Info" button on the MFD while turning the headlights on and off 4 times.
    Press the "Menu" field on the screen.
    Press the "Display Check" field.
    Press the "Signal Check" field.
    The 12v battery voltage will be one of the items listed, it should be above 12 volts. If it is lower, either the battery needs replacement or the charging system is not functioning correctly - see step 7.
    Put a small load on the battery by pressing the power button again without touching the brake pedal. The voltage should stay above 12v. If it drops significantly, you need a new battery


    I was reading 10V. Windows slow to move in ACC mode, so I checked online. eLearnAid has one for $165, local Toyota dealer was $174 here. Decided to go get it local and fix it tonight. Will post back if it works.
     
    #7 way0utwest, Jun 17, 2010
  8. way0utwest

    way0utwest New Member

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    Update: Replaced the battery and it's reading 14V in the signal check screen. It was pretty easy to do myself, but definitely more involved than any other battery I've changed. Will post some notes, tips, tricks.
     
    #8 way0utwest, Jun 17, 2010
  9. edthefox5

    edthefox5 Senior Member

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    How many times in the past have you had to jump that old battery?
     
    #9 edthefox5, Jun 18, 2010
  10. uart

    uart Senior Member

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    Hi Wayoutwest, after you've had time to test it make sure you let us know if the replacement 12V battery has any effect on your original problem of the HV battery losing charge. Everyone will be keen to know the outcome.
     
    #10 uart, Jun 18, 2010
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