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Optimal charging level leaving Prius Prime parked for long periods

Discussion in 'Prime Main Forum (2017-2022)' started by BChoAss, Jun 18, 2022.

  1. Gokhan

    Gokhan Senior Member

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    We don't know what the 8.8-kWh capacity exactly means. I don't think it's the capacity at a 100% depth of discharge, where you completely deplete the lithium in the anode, and different battery manufacturers may express the capacity at different depths of discharge.
     
  2. Salamander_King

    Salamander_King Senior Member

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    If you are going to dispute the published spec of the battery by the manufacturer... then I guess, there is no point in discussing on this topic any further.

    BTW, the spec is actually 8.79kWh.

    upload_2022-6-19_19-37-49.png
     
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  3. Gokhan

    Gokhan Senior Member

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    As I said, the way the capacity is defined varies with the manufacturer.
     
  4. Salamander_King

    Salamander_King Senior Member

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    As I said, if we can not agree on the manufacturer's published capacity of the battery, then there is no point in discussing what SOC is actually reserved.
     
  5. Gokhan

    Gokhan Senior Member

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    I think the recommendation from Toyota regarding waiting until the EV mode switches into the HV mode before turning the car off is an incorrect relic from the non-plug-in Prius manual. Every source is recommending 40–50% SOC as the ideal storage SOC.

    So, I would store the Prius Prime with 50% or perhaps a little less SOC for the longest battery life. In any case, you don't want to store it with a high SOC. I don't think it's good to store it with a low SOC either—again, I'm guessing that it's a relic typo from the non-plug-in Prius manual.

    Moreover, they recommend lower temperatures for storage for longer battery life.
     
  6. prius16

    prius16 Active Member

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    Fwiw, every battery manufacture has their own very specific, very proprietary, protected by tons of patents, battery chemistry and process.
    So, generalizations are just that - generalizations.

    Imho, heat is one of the biggest concerns with Li-ion battery life.
    So, people that live in Phoenix, and don't have a garage, car-port, shade, what-ever, are just plain screwed. :(

    What a lot of papers don't get into, is that most battery management systems will treat a Li-ion battery at a very low state of charge as bad. Do a search on Li-ion batteries, power tools, and "dead" (low voltage/State Of Charge) batteries.
    For many Li-ion batteries, being at a low state of charge for a "long" period of time, can be very damaging. Again, it varies massively dependent on the very specific battery in question.


    With the above said, below are some links with publicly accessible pdfs, graphs, etc.
    Imho, the first paper has some good info. However, the graphs, and the legends/colors used are hard to read and interpret.
    Note, hard doesn't mean impossible. :)


    Code:
    
    Extending Battery Lifetime by Avoiding High SOC
    https://www.semanticscholar.org/paper/Extending-Battery-Lifetime-by-Avoiding-High-SOC-Wikner-Thiringer/75d5911ad1092fe3c21f13fe1fce8b41aa88fac6
    
    Ageing mechanisms in lithium-ion batteries
    https://www.semanticscholar.org/paper/Ageing-mechanisms-in-lithium-ion-batteries-Vetter-Nov%C3%A1k/69c9a92885d9f94f6233a3029481f5e1f7f32fbd
    
    
    Memory effect in a lithium-ion battery.
    https://www.semanticscholar.org/paper/Memory-effect-in-a-lithium-ion-battery.-Sasaki-Ukyo/0e84b72cd955f879bc54111e1d1d8aeff6a96bc0
    
    
    A graph, again, it's not the easiest to quickly understand.
    Ageing in Commercial Li-ion Batteries
    https://www.semanticscholar.org/paper/Ageing-in-Commercial-Li-ion-Batteries%3A-Lifetime-and-Wikner/bdd82f19d2a3b5b58129a94a8d07694071aa77cd/figure/31
    


    .
     
    #26 prius16, Jun 20, 2022
    Last edited: Jun 20, 2022
  7. jerrymildred

    jerrymildred Senior Member

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    Yes. See the top picture in post #11.

    I use an app called EternalPower. It places a little controller in the menu bar that lets me set the battery charge wherever I want it and it stays there. I can also boost it to wherever I want for when I need to unplug, or I can let it drain to any point I want.
    Screen Shot 2022-06-20 at 7.30.35 AM.png
    Unfortunately, Google can't seem to find it anymore. IIRC, it was hard to find back when I downloaded it 1-1/2 years ago. But there are plenty of other apps that will do the job. 19 AlDente Alternatives – Top Best Alternatives

    Every app or tool that is able to display true SOC will disagree with that statement. The car absolutely must know the true SOC and that's the data that those tools access.
     
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  8. Marine Ray

    Marine Ray Senior Member

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    I finally put this graphic together. Helps me understand our traction battery. Probably not perfect, but pretty close. :)

    Traction Battery explained.jpg
     
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  9. Salamander_King

    Salamander_King Senior Member

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    Data and reasoning presented in my comment #20 which is supported by data from many others indicate that there is no extra 15% reserve buffer below the HV portion of the traction battery as shown in your diagram. And from the Toyota's own published spec, the usable portion of the traction battery for the EV operation should be ~6.3kWh not 5.3kWh as shown on your diagram.
     
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  10. Marine Ray

    Marine Ray Senior Member

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    You graciously reviewed my graphic months ago and gave it your endorsement. If it's incorrect kindly produce a similar graphic with a more accurate picture. Thanks.
    Posted via the PriusChat mobile app.
     
  11. Salamander_King

    Salamander_King Senior Member

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    I don't remember seeing your graphic before. The graphic looks fine except for the bottom 15% reserve and EV portion being smaller than Toyota's spec. Remove the bottom buffer and add that to the EV portion, it will fit the observed data and spec.
     
  12. bisco

    bisco cookie crumbler

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    how would you wait for a non plug in prius to enter hv mode? (n)
     
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  13. Trollbait

    Trollbait It's a D&D thing

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    I think Leafs that suffered the most in Pheonix were in garages. Those tend to not be air conditioned, nor have active ventilation. The space heats up from the sun on the roof, and the charging of the car. Without an active cooling system to move air, the hot air eventually stagnated around the battery, and cooked it. Sitting in the sun isn't ideal, but air heated by the battery had a chance to move away from the car.

    Thus why Li-ion batteries have protection circuits. That low charge damage is potentially dangerous. It has been deemed to call the battery bad than take the risk of recharging it from that state. So the circuit 'bricks' the battery. At least one person bought a Tesla Roadster as an investment. They put in storage without plugging it in. Check on the car a long time later, and the entire battery pack was bricked.
     
  14. Gokhan

    Gokhan Senior Member

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    I repeat again: I think Toyota made a mistake in the owner's manual. Depleting the hybrid vehicle (HV) battery to the point that the ICE starts before turning off the engine applies to the non-plug-in Prius so that the drivers don't store the vehicle with the HV battery around 100% SOC or even higher than 100% SOC.

    The Prius Prime should not be stored at 0% SOC, and it should be charged regularly. There was one poster who never charged the battery, and it died in a matter of a few years.
     
  15. jerrymildred

    jerrymildred Senior Member

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    This statement is in the 2017 Prime owner's manual. Nothing remotely like it is in the 2017 Prius manual:
    Screen Shot 2022-06-20 at 4.14.47 PM.png
    So it's not an artifact left over from the regular Prius manual since it's not in the regular Prius manual.
     
  16. Gokhan

    Gokhan Senior Member

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    It could be from another non-plug-in hybrid manual or written with a non-plug-in hybrid in mind.

    Storing a lithium-ion battery near 0% SOC to prolong its life seems to be unheard of everywhere else.
     
  17. Trollbait

    Trollbait It's a D&D thing

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    The standard hybrid's battery is never at 100% SOC. The NiMH pack isn't allowed to exceed 80%. The Li-ion might go higher, but not by much. The rare edge cases where the system allows the battery to exceed those limits also entail the system discharging it down as fast as possible. If the car is shutdown before that happens, NiMH has a notorious fast self discharge rate, and Li-ion loses the most charge from that over the first 24hrs.

    Waiting for the engine to kick on before shutting off the car won't harm the NiMH, it'll be around 60%, but it means the Li-ion pack is down around the 20% range. Li-ion handles lower SOC better than NiMH, but storing it there all the time isn't good for it.
     
  18. jerrymildred

    jerrymildred Senior Member

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    Depleted EV is not all that near 0% charge. But it is a little under the usual 20% minimum recommended by many systems. I leave mine anywhere from 50% to depleted. But I've never left it for more than two weeks. Longer than that and I'd like to have it at about 40% indicated.

    The instructions are not from an editing mistake but may be from misinformation supplied to the tech writers.
     
  19. Trollbait

    Trollbait It's a D&D thing

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    It wasn't in older Prius manuals.

    Toyota isn't calling for storing the battery at 0%, but within the SOC range used for the hybrid system. They are probably worried about extended storage in a hot location. With high heat, it's better to have a lower charge in terms of preventing damage.
     
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  20. Gokhan

    Gokhan Senior Member

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    14% according to @Salamander_King, minus the daily self-discharge.