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Prime Traction Battery Properties

Discussion in 'Prime Main Forum (2017-2022)' started by stevepea, Jan 16, 2019.

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  1. stevepea

    stevepea Senior Member

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    So you're saying it's better to keep the car stored with, say, 50% charge than 0% charged?
    (For arguement's sake, don't count the buffer... so "0%" would be where you run out of EV range and the ICE would come on if still driving).

    But.... that goes against what Toyota says in its manual. Though it's talking about longer-term storage, I would think the recommendations would still hold. The manual mentions somewhere that it's better to store (for longer periods) it without a charge than charged.

    Where did you get the data for your graph?

    So if I only use the car once every 5 days or so, for only about 8 miles (and leave it off in the garage all the other time) is it better to charge just what I need (approx) beforehand every 5 days, or to fully charge it once, and have it SLOWLY run down over the course of 2-3 weeks (just sitting in the garage as it runs down, which will take about 2-3 weeks). Thanks!

    And Washingtonian, yes, I can predict quite accurately that I only use the car about twice a week for about 8 miles each time -- just as it's been for the last few months. Life sometimes throws you situations that are not good, and I hope you never find yourself in such a situation. At any rate, though hopefully things will go back to normal in a few months (ie, lots of driving), as it's been for a while now -- and will be for at least another month or two, I pretty much drive 8 miles, twice a week. That's it. Which is why I asked this question in the first place.
     
    #21 stevepea, Jan 24, 2019
    Last edited: Jan 24, 2019
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  2. Lee Jay

    Lee Jay Senior Member

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    Actually, that's a different question, and it's more chemistry-dependent than the cycle life question.

    Actually, the manual contradicts itself on this topic.

    "●Leave a low level of charge in the hybrid battery (traction battery) when
    leaving the vehicle undriven for a long period of time.
    After confirming that EV mode has switched to HV mode, turn the power
    switch off."

    "■If the vehicle is not used for a long time
    In order to prevent the hybrid battery (traction battery) from becoming
    extremely low in charge, charge the hybrid battery (traction battery) from
    external power source or start the hybrid system at least once every 2 or 3
    months, and turn the power switch off after the gasoline engine has
    stopped automatically."

    But that isn't really true. However, some generalities can be drawn about all lithium ion chemistries:

    - Leaving the battery at full-charge is really bad for them.
    - Leaving the battery at full-discharge is even worse.
    - Somewhere in the middle is better, but the best charge for storage varies between 15% and 60% of a full charge depending on chemistry.

    Battery University's graph, not mine.

    It's better to rarely charge it to full charge, but not never (the cells need balancing at full charge once in a while). Try to charge it to 80% and discharge it to 40% (give or take your particular drive), and do the charging just before you use it.
     
    #22 Lee Jay, Jan 24, 2019
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  3. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    Are the % charging numbers in the previous postings referring to the true battery state of charge (SOC), or the values reported on the car's user interface? "empty" on the display is really around 18% true SOC, and "full" is around 80% true SOC.
     
    #23 CharlesH, Jan 25, 2019
  4. Lee Jay

    Lee Jay Senior Member

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    Both (confusing, sorry).

    The graphs are true state of charge as are the comments about storage. When I refer to the car's state of charge, I'm referring to the reported EV range percentage.
     
    #24 Lee Jay, Jan 25, 2019
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  5. Synergy3221

    Synergy3221 Junior Member

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    I worried about this for the first few months of my ownership of my prime, trying to time when to unplug it so it would be at 80%.

    Then I realized how stupid this was. If I lose 5-7 miles of range in 3-5 years who cares. I live in the northeast so we don’t get extremely hot temps.

    Also I don’t plan on keeping this car for more than 3 years, especially with the smattering of pure EV’s to choose from out there.
     
    #25 Synergy3221, Jan 25, 2019
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  6. Lee Jay

    Lee Jay Senior Member

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    I kept my last Prius for 13 years, so battery degradation matters to me.
     
    #26 Lee Jay, Jan 25, 2019
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  7. stevepea

    stevepea Senior Member

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    Absolutely. I've never had a car for less than 10 years, and I only have one car at a time, so this kind of stuff matters to me as well (and my current situation of driving only a few local miles each week, nothing else, looks like it will probably continue for a couple more months).

    Just a comment: at the point when the EV range is completely "gone", the battery is still about 25-30% charged (because of the buffer), so at least it's not at "zero" as far as the actual state of the battery...
     
    #27 stevepea, Feb 9, 2019
  8. bisco

    bisco cookie crumbler

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    good protection there, smart move by toyota.
     
    #28 bisco, Feb 9, 2019
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