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Is my traction battery going bad?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by jdonalds, Jun 28, 2015.

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  1. jdonalds

    jdonalds Active Member

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    Okay I checked the 12V battery no load and load. It stays above 12.1V.

    I also did strawbrad's charge/discharge test without the cable and software. It took several minutes to charge and to discharge. That suggests a better HV battery than I have been thinking. I'm now anxious to get my hands on the cable and software. I hope the software works on my Windows 8.1 laptop.

    Next I'm going to do enough disassembly to get to the HV fan and clean it.
     
    #41 jdonalds, Jul 2, 2015
  2. bisco

    bisco cookie crumbler

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    no load 12.1 is a bad battery. it either needs a charge, or needs to be replaced.
     
    #42 bisco, Jul 2, 2015
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  3. dani1166

    dani1166 Junior Member

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    I was experiencing the same symptoms with the bars rapidly decreasing in charge then charging quickly back up. Noticed it for about a year or 2 before the warning lights finally came up. My car is now being fitted for a new hv battery. For me those were the symptoms that got me concerned. I didn't act on it though i put up with it until now.
     
    #43 dani1166, Jul 2, 2015
  4. jdonalds

    jdonalds Active Member

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    It was 12.4V no load. Under load, even after a full minute of load it didn't drop below 12.1V.
     
    #44 jdonalds, Jul 3, 2015
  5. bisco

    bisco cookie crumbler

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    12.4 is on the edge imo, although, may not be the cause of your problem. a new battery with a full charge will be 13+.
     
    #45 bisco, Jul 3, 2015
  6. uart

    uart Senior Member

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    I'd say your 12V battery is fine. When I replaced my 12V battery a few years ago it only measured 12.3 to 12.4 volts no load (in car measured) even from new.
     
    #46 uart, Jul 3, 2015
  7. jdonalds

    jdonalds Active Member

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    I cleaned the fan today. It was actually pretty clean considering 7+ years of use. The good news is if I end up replacing the HV battery I've already experienced about 90% of the tear down needed. It was also a good opportunity for a deep cleaning, especially considering areas exposed which are normally not accessible for cleaning.

    I spent about two hours total, including shampooing the rear seat and the rear carpet pad.

    Cooling fan prior to cleaning
    [​IMG]

    Not much dirt considering 7+ years of nearly daily Prius use.
    [​IMG]

    Cleaned and going back into the car
    [​IMG]

    Cleaned cooling fan
    [​IMG]

    Waiting for the cable and software...
     
    #47 jdonalds, Jul 3, 2015
    Last edited: Jul 4, 2015
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  8. uart

    uart Senior Member

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    Yeah that didn't look too bad. Was still worthwhile cleaning it though. :)

    JDonalds, you probably have a similar amount of traction battery capacity loss as my 2005 Prius has. These batteries don't always just go from full performance straight to failure. In the same way that power tools, mobile phone and laptop batteries go, many of us will experience a gradual decline in battery performance rather than a sudden death, and that is what you are seeing.

    If you look at the true underlying state of charge versus the displayed bars it looks like this:
    Prius_ComplexSOC.jpg
    Notice how bars 4 and 5 are relatively short, especially compared to bars 6 and 7. This is why you can lose these bars so quickly as the traction battery loses capacity.

    The following image shows how I believe an aged traction battery appears to operate. Notice where I have mark the "charging anomaly" and the "discharge anomaly". An aging pack like this operates in two distinct states, a "bottom referenced" state and a "top referenced" state.

    After the battery has been discharged down to about 3 bars it enters the "bottom referenced" state. From here, as it charges up the bars 3, 4, 5 and 6 behave perfectly normally (that is, they hold a similar amount of charge as per a healthy battery). When however the charge level reaches the point in the 7th bar where I have marked "charging anomaly jump", the battery management suddenly realizes that the pack can take no more and transits rapidly to full 8 bars and it's upper charge limit. Notice that at this point it actually has about 10% less charge than it really should.

    Now that the battery has maxed out, it enters the "top referenced" state. From here as the battery discharges bars 8, 7 and 6 appear to operate perfectly normally (similar amount of charge as per a healthy pack). When however it reaches the point I have marked as "discharge jump anomaly", then the battery management first starts to notice that missing 10% charge, and you get the relatively rapid readjustment of the SOC from 6 bars down to 3. This is not usually instantaneous, but typically happens over a short period like about 15 to 20 seconds, sometimes even with the engine running and the battery display indicating green charging arrows.

    Given that you have quite a lot of mountains around you up there in Redding, I expect that you are quite often entering this "top referenced" battery state, and consequently are often seeing this "discharge jump anomaly", just as I do.

    Prius_ComplexSOC2.jpg
     
    #48 uart, Jul 4, 2015
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  9. kinglew

    kinglew Member

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    those were they same way my 2005 acted. exept mileage change was not as drastic change.park car with it still running run air on high watch display it will throw code also red symbol.good test for battery capacity under load also recharge capacity. if it failing it will fall do this
     
    #49 kinglew, Jul 4, 2015
  10. jdonalds

    jdonalds Active Member

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    Here's my thinking. If the cable and software show the HV battery indeed is experiencing one or more poor performing cells I will replace the battery. I see no benefit to waiting until the car throws codes unless it is simply because I'm close enough to 150K miles to press Toyota for a free exchange. For that reason I might wait a few weeks. I have no idea how far past 150K miles Toyota would go to give me a fresh battery.

    If I'm going to spend $2K'ish to replace the HV battery it seems better to do it sooner as we are dumping fuel as it is. We continue to see less than 35 mpg average. Today I noticed the ICE came on right away when moving away from a stop sign. Normally I'm light footed enough to at least drive on EV for a few car lengths before the ICE kicks in.

    There is no way I'm going to drive several more months, or even a couple of years, getting 10+ mpg less than normal.

    Uart: Yes you're right about the hills but we aren't up in the high elevations around Redding. We live about 250' above Redding city level. So when we leave home and head down the hill, which is about a mile from our house, normally we have green on the charge bars when we hit the bottom of the hill. Today we actually left home on green because I had force charged the HV battery in the garage last night just for fun. When we reached the bottom of the hill we didn't see green today. Our 7 mile journey today achieved only 24 mpg on the SCAN II. I could previously make that same round trip and hit the low 40's at least.
     
    #50 jdonalds, Jul 4, 2015
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    In my post #11 I suggested several possible areas for you to check. Have you checked any or all of them?
     
    #51 Patrick Wong, Jul 4, 2015
  12. jdonalds

    jdonalds Active Member

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    1. Check tire air pressure - DONE
    2. Raise up the rear of the car and spin the rear wheels when the parking brake is off, to make sure there is no drag
    3. Check wheel alignment
    4. Check engine oil level - DONE
    5. Check transaxle ATF level, replace ATF if more than 60K miles since last ATF drain/refill - DONE
     
    #52 jdonalds, Jul 4, 2015
  13. SageBrush

    SageBrush Senior Member

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    Are you saying your battery lost two bars of SOC while going downhill ? That does not sound good.
     
    #53 SageBrush, Jul 4, 2015
  14. jdonalds

    jdonalds Active Member

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    Exactly, or at least one bar. Started out green, ended up blue.
     
    #54 jdonalds, Jul 4, 2015
  15. SageBrush

    SageBrush Senior Member

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    Worrisome for sure, but it is not a definitive test unless you can say with some confidence that the car in the past always gained SOC bars.
     
    #55 SageBrush, Jul 4, 2015
  16. bisco

    bisco cookie crumbler

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    that can't be good. if it's green, it's probably gonna start burning off juice, but it should stay green i think.
     
    #56 bisco, Jul 4, 2015
  17. jdonalds

    jdonalds Active Member

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    Well it always gained bars on that hill. If I was driving I would normally see green at the bottom of the hill. My wife not so much. I was driving today and as I said I actually started out green which was rare if it ever happened. Last night I had just finished cleaning the HV fan and putting everything back together. I had dropped a plastic clip behind the 12V battery so had to remove the battery to get it. I was making sure everything was working properly and in the process I did the trick to charge the battery to green. It quit charging when there was only one green bar; it wouldn't fully charge both green bars. Nonetheless I started out green in the garage, by the time I hit the top of the hill I had lost the green bar, and it didn't recover by the bottom of the 1/2 mile long hill. Normally I can pick up two bars on that hill.
     
    #57 jdonalds, Jul 4, 2015
  18. SageBrush

    SageBrush Senior Member

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    I suspect you are seeing an artefact of your forced charging and I would not read too much into the test.

    You can drive yourself crazy, or wait for the cable and do a proper test. I know which I would choose.
     
    #58 SageBrush, Jul 4, 2015
  19. jdonalds

    jdonalds Active Member

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    Well it was just an observation. But nonetheless our mileage is under 35 mpg so something certainly is going on.

    What's killing me is I can easily get the itch to buy a new car. I'm anxious to get some real specs and prices on the 2016 Prius and now the 2016 Rav4 Hybrid. Both are a few months away and with this battery thing I wish it would all happen tomorrow instead of that far into the future. The cable/software delivery is suggested to be July 14-15. Ugh.
     
    #59 jdonalds, Jul 4, 2015
  20. bisco

    bisco cookie crumbler

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    9,000 miles /45 mpg x $3./g = $600.

    9,000 miles / 36 mpg x $3./g = $750.

    $25./mo. ride it out.:)
     
    #60 bisco, Jul 4, 2015
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