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Prius Gen 2 Hybrid Battery End-Of-Life

Discussion in 'Gen 2 Prius Technical Discussion' started by LewisM, Sep 13, 2015.

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  1. LewisM

    LewisM Junior Member

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    (Opinion of an ordinary owner, not an expert.)

    (a) How do I know when my hybrid battery will fail? You cannot know for sure. Battery failure is not defined by the car’s Energy Monitor by loss of energy storage capacity, but by when the voltage of a single cell (of the 14) drops more than about 1.2 volt below the maximum voltage of other cells. This voltage difference triggers the Energy Monitor alarm (red triangle). An excellent discussion of this is given here Predictive battery failure analysis for the Prius Hybrid (A USB cable and Techstream diagnostic software are available on ebay for about $26.)

    Notice that it is voltage difference from cell to cell, and not battery capacity that triggers the alarm. That said, Prius batteries less than 8 years old rarely fail. An aged battery with greatly reduced capacity is much more likely to suffer a bad cell, and that bad cell may appear quite suddenly. Furthermore, the aging process snowballs. Each time the battery is cycled (charge-discharge) it loses some capacity. The deeper the cycle, the greater the aging. However, as capacity is lost, the cycle is forced to go deeper to compensate, and into a death spiral.

    (b) How do I estimate hybrid battery capacity? The simple test I use is measure the time for traction motor to pull down one, full bar on the State of Charge (SOC) display. Turn off air conditioning and any other electric uses, park car with handbrake on, and leave in Drive, so as to put a steady, consistent drain on the battery. Use the same SOC bar each time. I use bar 6, the top blue bar, parking the car with 7 bars displayed, so I can get the true, full time on bar 6. On my car, with a new hybrid battery, bar six is displayed for 13 min and 10 sec. Two months before the old battery failed, this time was down to 2 min, yet even then the maximum cell-to-cell voltage difference was only 0.16 volts. In other words, judging by cell-to-cell difference, my battery was almost like new. On the other hand, judging by energy storage capacity, this battery had lost 85% of its power. I was surprised that the car could still run OK with such a poor HV battery, but cannot complain about 185,000 miles and 9-1/2 years. (Yes, battery capacity also depends on ambient temperature, so don’t expect to get the same numbers in January as you do in July. That said, battery cycle age is a much greater factor than temperature.)

    (c) What should I do about an “old” hybrid” battery? Probably nothing. When the red triangle of death appears, simply drive to your Toyota dealer or battery shop and bite the bullet. I’m happy to give my infrequent repair business needed to the fine dealer here in South Carolina. Besides, there are no hybrid battery shops nearby. I have no idea how far you can safely drive once the Energy Monitor warning has displayed. However, knowing what I know now, when the SOC bar 6 discharge time got down to 2 minutes, I would have been wise to plan a trip to one of the cities that has a hybrid shop and saved myself a lot of money.
     
    #1 LewisM, Sep 13, 2015
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  2. JC91006

    JC91006 Senior Member

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    (d) if you're out of warranty, you may want to invest in a grid charger and rebalance/recharge your battery before it gets too weak.
     
    #2 JC91006, Sep 13, 2015
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  3. bisco

    bisco cookie crumbler

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    luckily, most will never have to worry about this.
     
    #3 bisco, Sep 13, 2015
  4. wjtracy

    wjtracy Senior Member

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    You've done well.
    The most reliable and preferred fix is a new Toyota batt.
    Total job costs $3500-4000 at Toyota, but one option is to request out-of-warranty assist and in some cases that could get you down to $2000 or so, assuming you get favorable ruling. If you go that route, it can easily take a week or two to get a ruling, so some planning for alternate wheels is needed.
    Advanced DIY's can fix the cells but even some advanced DIY's don't have the time to fiddle with it.
    If you absolutely need to get the Prius back on the road soon, sometimes that's a time to use a service such as Greentec or Dorman for rebuilt batt.

    As far as pushing life out, some say a few minutes warm up helps to ease the burden on the aging battery. If you start in Park, the engine comes on after a few secs, and then goes off after a minute or two. Then go. I try to do this, but especially if the car has sat unused for a few days I think it helps.
     
    #4 wjtracy, Sep 13, 2015
  5. CooCooCaChoo

    CooCooCaChoo Active Member

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    How accurate is the SoC indicator on the MFD tho?
     
    #5 CooCooCaChoo, Sep 14, 2015
  6. jeff652

    jeff652 Senior Member

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    This is been the common misconception for a while. Fortunately, there is a lot more than 'nothing' that can be done :). Our products have extended the life of hundreds of Prius batteries around the world already and are being used in fleet vehicles across the US.

    Why maintain the rest of the car but ignore the hybrid battery? When installed and used regularly on a healthy hybrid battery, a Prolong Battery Charger will significantly delay the erosion of the hybrid battery cells. This battery erosion is what leads to failed battery packs.

    Battery reconditioning is a recurring maintenance process used to increase the usable battery pack capacity and extends its service life. Battery reconditioning is not a one-time event. If performed once and never repeated, the benefits of battery reconditioning will be short lived, often less than a year. Proper battery reconditioning as a recurring maintenance process can significantly extend the service life of the hybrid battery pack.

    You can learn more about them here:
    Prolong Grid Chargers - Hybrid Automotive - Extending the life of your hybrid
     
    #6 jeff652, Sep 18, 2015
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  7. MTL_hihy

    MTL_hihy Active Member

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    I can personally say that I drove mine for over a year with it constantly throwing block error codes before I had time to rebuild it. It's not a big deal unless your battery is really on it's last legs. Everyone should at the very least own a mini VCI setup so you can see what the situation is if the battery shows a possible failure.
     
    #7 MTL_hihy, Sep 27, 2015
  8. bikes4u

    bikes4u Member

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    So it will be possible to drive it for a while after the red triangle shows on dash? Good to know.
     
    #8 bikes4u, Sep 29, 2015
  9. Rph74

    Rph74 Active Member

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    I know I am resurrecting an old thread here, but my 2006 Prius with almost 147000 miles took 18:35 to go down 1 bar on the SOC.

    In contrast, using the timed test procedure that S Keith devised in another thread, my battery only made it 4:21 which translates to about 40-44% battery rated capacity.

    Only time will tell how much longer my battery has, but I wishfully think and hope that your test means good news for me. This car mainly sees highway miles, and I tend to drive my other vehicles when it gets very hot outside.
     
    #9 Rph74, May 22, 2016
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