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2002 100% battery problem

Discussion in 'Generation 1 Prius Discussion' started by kbbpll, Sep 14, 2021.

  1. kbbpll

    kbbpll Junior Member

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    Our 2002, 279,000 miles, had an issue a couple weeks ago that happened again this morning. The energy display shows the battery 100% charged during normal driving, the engine runs while stopped with the display arrows indicating that the battery is being charged, even though it's at 100%. While driving, the arrow to/from the battery rarely points toward driving the car, but instead indicates the engine is driving the car and charging the battery. Again, despite the battery showing 100%.

    There are no warnings or lights displayed when this happens.

    In its younger days, the only times the battery showed 100% was during long descents down steep mountain passes.

    When it happened a couple weeks ago, it fixed itself and drove normally. Today when I dropped my kid off, I shut off the car and restarted it. Then it also ran normally on the way home.

    Obviously it's not fixing itself, so I'm curious what the problem could be and how soon whatever is doing it will just fail completely. The HV battery has never been replaced nor had any maintenance done as far as I can recall. Other than the usual stuff there have never been any major issues.

    About 6 months ago we had the big red triangle and it was code P3009 "high voltage leak detected". The shop couldn't repeat it, I had them flush the transmission fluid (since I read that dirty tranny fluid could cause it), and that problem has not repeated.

    Any suggestions about what the 100% battery problem is would be appreciated. Thanks.
     
    #1 kbbpll, Sep 14, 2021
  2. bisco

    bisco cookie crumbler

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    could be corrosion. time to pull the battery and have a looksee
     
    #2 bisco, Sep 14, 2021
  3. ChapmanF

    ChapmanF Senior Member

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    The car knows a battery conditioning routine it can run through every now and then. When I had my Gen 1, I described it in this thread.

    Assuming that was what it was doing, it's clearly a normal thing for the car to do, though of course the car may choose to do it more often as the battery gets long in the tooth.

    My 2001 was still on the original battery when I posted that, and still was six months later when I sold it after a collision. While I had caught the car doing that three or four times (in the eight years I owned it), it had never given me a battery code. I did hear later, from the person I sold it to, that a battery code had appeared. He runs a hybrid shop, so easily changed the battery when it happened.
     
    #3 ChapmanF, Sep 14, 2021
    mroberds and ammdb like this.
  4. kbbpll

    kbbpll Junior Member

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    Thank you for the replies. That's a very interesting thread from 6 years ago, @ChapmanF . Any idea how many miles were on it at the time?

    I'm not a big DIY and the thought of messing with a bazillion volt battery scares me a little. Yes @bisco I'm sure there's probably corrosion in there. Would having a pro pull it and clean it add some longevity? We live in CO, a fairly dry environment.

    I starting watching the Energy screen a bit more lately since it goes into a mode where it struggles to climb the steep hills we have around my house. Battery goes down to a quarter and there's no oomph coming from there, it's all ICE power and the car feels like a dog. Barely 30 mph with it floored where we usually do 40+ no problem. Then the next time on the same hills it's fine. We went through a phase where the mpg was really bad, low 40s on hot summer tanks where normally get 52+. I wrote it off to the new tires & rolling resistance, but I suspect it's the battery. The P3009 mentioned above, the sporadic hill climbing problem, and this 100% battery thing tells me we're finally slowly losing her.

    I suppose we "just drive it" until it dies. Moon Beam has had a good run, 19+ years and the most miles I've ever put on a car, virtually problem free. I really love the sedan design of the Gen1 and will hate to lose that. Best car I've ever owned.
     
    #4 kbbpll, Sep 14, 2021
    ammdb likes this.
  5. ChapmanF

    ChapmanF Senior Member

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    Let's see, I posted that in mid-October 2015, looks like it would've been just under 228,800.

    I would not necessarily take it out and molest it. What you can find is that all the copper surfaces you can see are hella corroded. The electrons are only going where you can't see, between the terminals, the bus plates, and the nuts, and if the nuts were properly torqued at the factory, they've been gastight and you will find shiny metal underneath them.

    But to do that, you would have taken them off, and then you've got yourself a job cleaning everything up.

    The battery ECU monitors "internal resistance" per block of two modules, and if you have a scan tool to watch those values, you can see if the measured resistance is going up. It will include the connection resistances (because the ECU's monitoring wires aren't poked directly into the modules).

    In an ancient battery, the actual internal resistances (inside the modules) are likely to be legitimately elevated anyway; high numbers there won't indicate corroded-connector problems necessarily. I might investigate if it looked like there were noticeably higher resistances in a few places.

    There are a couple more common ways that corrosion can make itself known in a battery. It can create electrical leakage paths to body metal (you'll get a P3009 code), or it can eat away the skinny wires that the battery ECU uses to measure block voltages and resistance. That'll give P3030 and weird voltage readings on your scan tool, where one block might show zero or negative numbers while one right next to it could look doubled, that kind of thing.

    Edit: I skimmed your post and wrote the above without actually seeing that you already have a P3009. Yes, that's a reason to go in there and deal with some corrosion. Or look for a battery. Or move on.

    When those things start happening, then there's a reason to go in.

    If you're feeling proactive, looking at the condition of those skinny wires can be a proactive thing to do. Corrosion will often mess up the big orange connector where they all plug in to the ECU.

    [​IMG]
     
    #5 ChapmanF, Sep 14, 2021
    mroberds likes this.
  6. kbbpll

    kbbpll Junior Member

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    Thanks for the additional feedback. I like projects but this is something beyond my abilities or inspiration, and it also sounds like something a shop would spend many hours on (i.e. expensive). I'll talk to them; perhaps just replacing the battery would be more cost-effective in the long run. It still drives like a champ most of the time.
     
    #6 kbbpll, Sep 15, 2021
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