A question about "cycled" charging through the 120v adapter and battery longevity

Discussion in 'Prime Plug-in Charging' started by Pdog808, Apr 11, 2017.

  1. Pdog808

    Pdog808 Active Member

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    I have access to free 120v charging outlets at work, but an annoying feature is that they cycle charging for each outlet on and off for at least half an hour time periods. This is to avoid blowing the parking structure power breakers.

    Will the constant on and off power charge affect the battery longevity (i.e. damage it)? It is extremely annoying in practice as 6 hours of this cycled charge resulted in my Prime only achieving about 50% capacity.

    Another question - someone mentioned that leaving the battery charge maxed out for "long" periods of time could be detrimental to battery life. Is there a hard number to the amount of hours that you can leave the battery at max charge before driving? I will possibly soon have access to an L2 charger but if I charge it when I first get into work, it will be "topped off" for another 6 hours before I leave. One advantage is that I can charge very early in the morning and move the car under shade for the remainder of the day.

    Thanks!
     
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Since November 2016 when the first Prime went on sale, not a single one has had a battery replacement reported. Based upon the existing statistical analysis:

    THEY LAST FOREVER!

    Of course I'm pulling your leg.

    If you really want an answer, get identical chemistry batteries and put them in a set of thermal cells with computer controlled, chargers and load. Then do the experiment: cycle the batteries at different temperature and load profiles and report the failure rate.

    Once upon a time, NiMH was the only practical, rechargeable battery. The chemistry was well defined and operation characteristics had at least 10 years of scientific inquiry. But now we have at least five LiON chemistries and at least three cell formats: (1) sealed cylindrical; (2) prismatic, and; (3) polycell. Fortunately, you can simplify the testing.

    Buy a Toyota Prius Prime battery pack and disassemble into individual modules. Plan a test regiment with multiple temperature profiles: (1) Northern USA; (2) Midwest USA, and; (3) Southern USA. Then setup at least three charge-discharge profiles: (1) to the stops; (2) headroom, and; (3) hybrid only mode.

    My count suggests this is 3x3 or about 9 test scenarios. This is likely more than the number of cells in the battery pack. So double-up the most likely temperature and charge-discharge profiles and leave the outliers just as a way to look for pathological cases.

    Personally, I think we should wait about a decade when we'll have a significant population of Prius Primes and the associated LiON-style including other Toyota hybrids. Use this larger population to look for trends.

    Bob Wilson
     
    #2 bwilson4web, Apr 11, 2017
    Last edited: Apr 11, 2017
  3. Pdog808

    Pdog808 Active Member

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    Hah - interestingly enough I used to work in the environmental test field. Digital hardware, not batteries though.

    I base a lot of my expectations on NiMH limitations, I guess. Trying to keep charge cycles to a minimum and heat even more so.

    I may end up using the L2 chargers when they become operational (over 2 dozen chargers just sitting there due to no power!).
     
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  4. bisco

    bisco cookie crumbler

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    i can't see why it would be a problem. the car itself basically 'cycle charges the batteries, and toyota does not warn against it.
     
  5. Piwacet

    Piwacet Junior Member

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    I was hoping I wouldn't have to do that... :)
     
  6. Pdog808

    Pdog808 Active Member

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    @bisco - good point about the batteries being cycled at a much faster rate during normal use. The round robin charging is pretty annoying, though.
     
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