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Prime 2nd gen battery size - usable vs installed

Discussion in 'Prime Technical Discussion' started by pakitt, Jan 1, 2023.

  1. pakitt

    pakitt Senior Member

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    I am pretty sure that this has been asked and answered in some other post, and I apologize if this is a repeat, but I cannot find an answer using the forum search.
    What is the gross battery size of the Prime (2nd gen) and how much of it is usable?
    Wikipedia says (because looking for this information on Toyota's website is a nightmare) it is 8.8kW. Somewhere in the forums I found that usable is 6.2kW.
    Is there really a 30% buffer? that much?

    If that is the case, for the 3rd gen coming out this year - Wikipedia and Toyota.it (the only official Toyota website where I could find the number) say that the battery will be 13.6kW. Available to charge then will be 9.5kW? (i.e., 13.6 - 30%) or another number?
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    What model years of Prius Prime are you talking about? These “gens” are too confusing?
     
  3. pakitt

    pakitt Senior Member

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    2016. See linked article in Wikipedia. I bought the car in Feb. 2021.
     
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  4. Salamander_King

    Salamander_King Senior Member

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    The size printed on the PP's traction battery casing says it is 8.79kWh, but 8.8kWh has been the accepted value for this battery. As for the actual usable capacity, it really depends on who you ask and how you measure. The 6.2kWh is probably about average. If you are dipping into the HV portion of the traction battery, then you can get a bit more. And if you are stopping right at when the EV switches to HV, then it may be a bit less.

    upload_2023-1-1_12-2-30.png
     
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  5. pakitt

    pakitt Senior Member

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    Thank you. I also rely on what the charger tells me when I go from 0% to 100% charge.
    I forgot that the 30% buffer contains the HV mode “battery” charge.
    What is the overall battery buffer then reserved for longevity?
     
  6. Salamander_King

    Salamander_King Senior Member

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    No one knows the exact % of kWh in the traction battery Toyota programmed deemed to be "untouchable". But extrapolating from the data, it looks like the upper buffer is ~16% and the lower buffer is less than 10%.

    The graph below is the SOC displayed on the dash vs the "actual" SOC reported by the HA app via ECU. SOC 100% on the dash corresponds to about 84% SOC and SOC 0% is about 14%. This lower 14% includes the amount used for the HV mode, so the actual "reserve" is likely to be less than 10%.

    upload_2023-1-1_12-30-40.png
     
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  7. pakitt

    pakitt Senior Member

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    Thank you very much for all the details.
    I’ll use the same assumptions as I calculate how much of $$$ I could get from a 2023 vs my current 2021.
    But the prime is already SO efficient, that it will be not much at all. At that point I’d get a 2023 for other reasons other than energy savings.
    Coming from a regular 20-30mpg ICE vehicle, even at US gas prices, the Prime (or any hybrid or EV) would save you hundreds per year.
     
  8. Salamander_King

    Salamander_King Senior Member

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    Yeah, for all new 2023 (or maybe 2024) Toyota Prime without incentives (manufacturers rebates) and tax credits, my guess is that it will never save you money by replacing your 21 PP to 23 PP. I recently traded in my 21 PP for a 22 Ford Escape PHEV. This swap alone would not have saved any money, but with an increased EV range of Escape (EPA-rated 37 miles) over PP (EPA-rated 25 miles), I projected to use less gasoline albeit more total fuel cost.
    see my opening comment on this thread: No more Prius Prime. | PriusChat

    But the main reason I made the trade was to get the tax credit this year (on the 2022 tax form) and consolidate our two vehicles (Prius Prime and Pathfinder Hybrid) into a single car. If everything goes as I planned, then, I would cut down the total automobile-related cost including the gasoline cost by more than half this year.
     
  9. Marine Ray

    Marine Ray Senior Member

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  10. Salamander_King

    Salamander_King Senior Member

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    You keep showing the diagram without supportive data. As I commented last time when I saw you use the diagram, there is no evidence or data presented that I am aware of which indicates that there is a bottom 15% buffer below the HV portion of the traction battery SOC.
     
    #10 Salamander_King, Jan 1, 2023
    Last edited: Jan 1, 2023
  11. pakitt

    pakitt Senior Member

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    I have to agree with @Salamander_King. When I reach 0% SOC in EV mode and I recharge the battery at, e.g., ChargePoint, I get "fuel-ups" of about 6.2kWh. There is no reason to think the HV portion of the battery is any different than the regular Prius, so it should be around 0.75kWh. I would also assume it is 100% available (no buffer for the HV portion, which is a logical allotment, not a physical one). Hence, what is remaining of the overall battery as a buffer is 1.85kWh or about 20%, not 30% as per graphic.

    Therefore, in the new Prime 2023 (gen 3), assuming they are using the same allotments, removing 1.85kWh as buffer and 0.75kWh for HV driving mode, would leave 11kWh for EV-only driving. That would equate, assuming all other things are the same (including the car's weight and tire rolling resistance) to a total range of 51.7mi vs the 29.7mi I get today at my 4.7mi/kWh average. That would be a 75% increase in EV-only range.

    If, instead, the buffers are not absolute, but a % of the battery, then a 20% buffer for the new 13.6kWh battery would equate to 2.72kWh (and not 1.85kWh), leaving 10.13kWh for EV-only driving after removing the 0.75kWh required for the HV driving mode. That would yield 47.6mi range @ 4.7mi/kWh in my case, or an improvement of 60% vs the previous generation.

    In any case, the increase in EV-only range would be well above the 50% mentioned by Toyota. Unless...the new 19" wheels and the (extra?) weight would eat into the gains of a bigger battery, bringing "only" 50% increase.

    Getting a new Prime 2023 to replace my 2021, based on the above, would bring savings in terms of gas and electricity of about $50-100 over two years of ownership. Essentially zero benefits. I would surely emit even less CO2.
    And if you factor in the registration of the new car and higher insurance (new car vs a 3 year old one) I would "lose" money in fixed costs.

    I would of course get almost twice as much power, more "oomph", bigger trunk space, and finally a more modern entertainment system with wireless CarPlay. Of course Toyota had to go cheap with the screen and cameras, so their resolution, I am reading and hearing in reviews on YouTube, is not up to a 2023 car...
    I am also hoping that the TSS3.0 will bring an LKA with lane centering that doesn't "wiggle" like on my current Prime (hence, always off), and that the new "traffic assist" is working well, instead of being a beta version to be improved in TSS4.0. Oh wait, there are OTA updates - maybe we will really get updates that improve on the software, instead of having to buy a brand new car...
     
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  12. Marine Ray

    Marine Ray Senior Member

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    I respectfully ask you to make your own diagram based on mine. I'd favorably consider your diagram.
     
  13. Salamander_King

    Salamander_King Senior Member

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    Here it is. The number of kWh and percentage are off but it represents more accurately the real proportion of the SOC used for each category.

    upload_2023-1-2_10-10-41.png
     
  14. Marine Ray

    Marine Ray Senior Member

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    Thanks. What's your evidence that there is no bottom buffer?
     
  15. Salamander_King

    Salamander_King Senior Member

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    As I commented before, no one knows for sure. At least from the data reported by the HA app, the bottom buffer is included within the bottom ~14% of the HV portion of the SOC. I could drive the car on HV mode down to SOC 7-8% shown on the HA but not lower. My guess is that is the real lower limit of the usable SOC. But this lower limit changes how the car is driven and other conditions, so I don't think it is a hard set absolute % of the SOC.
     
    #15 Salamander_King, Jan 2, 2023
    Last edited: Jan 2, 2023
  16. bisco

    bisco cookie crumbler

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    there has to be a minimum to prevent battery damage, and leave enough power to start the engine
     
  17. vvillovv

    vvillovv Senior Member

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    I think what you're seeing is what most members here believe is a pretty good estimation (some have clocked it using kilawatt and reading off L2 charge stations) of what the pack takes in while charging.
    I seen and agree with a 2017 estimation of 8.89 rating, 6,5 at the plug, 5.5 to the wheels.
    except of the rating, the others are variable, but close enough for gov work.
     
  18. billvon

    billvon Junior Member

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    The 8.8kW includes a buffer to protect the battery from damage. If you try to take it below that the battery's BMS will shut down the battery's output and the car will come to an exciting stop.

    If you really took it all the way down to zero voltage you might get another .2kwh out of the battery, but that would be the last time you could use the battery. Perhaps that buffer is what you are thinking of?
     
  19. bisco

    bisco cookie crumbler

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    yes, were they speaking of another buffer?