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Amount of battery used for EV only driving

Discussion in 'Prime Fuel Economy & EV Range' started by davidewart45, Aug 25, 2022.

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  1. davidewart45

    davidewart45 Junior Member

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    I have a 2020 Prius Prime. The specs say it has an 8.8kWh battery.
    But I am just now experimenting with an energy monitor to track charging (using a standard 110V).
    Plugging in from empty to full charge showed as 6.2kWh.
    Is this because the hybrid mode reserves 2.6kWh of the battery's capacity?
    Given that the traction battery is not drained to zero before the hybrid mode kicks in, what is the trigger point? How much charge is needed to "fill" the traction battery by plugging in?
     
    #1 davidewart45, Aug 25, 2022
  2. schja01

    schja01 One of very few in Chicagoland

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    If the traction battery is less than 30% charged you won’t be able to engage EV mode and you get a message saying so. That’s 30% of the total traction battery not the EV portion.
     
    #2 schja01, Aug 27, 2022
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  3. Tideland Prius

    Tideland Prius Moderator of the North
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    Not all of it is for the hybrid mode. There is reserve for longevity too. 8.8kWh is the gross capacity and you’ll never have access to the full amount, especially if you want it to last 8-10 years and the 160,000-240,000km warranty.

    @john1701a website will have more information but IIRC, a full charge (100% on the battery meter) is about 84% true SOC. (So there’s a 16% top buffer) and “empty” is 14% true SOC with a drained HV portion dropping that to 11% true SOC.

    Taking 84% to 14%, that’s 70% of the battery. 70% of 8.8kWh is 6.16kWh. Yeah that’s close enough to what you’re reporting.
     
    #3 Tideland Prius, Aug 27, 2022
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  4. Marine Ray

    Marine Ray Senior Member

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    This grahic I created helped me understand better. Traction Battery explained.jpg
     
    #4 Marine Ray, Aug 28, 2022
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  5. Salamander_King

    Salamander_King Senior Member

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    Your 6.2kWh on L1 for a full charge is rather low. With L2 EVSE, I have read reports by others saying 6.0-6.3kWh for a full charge is common. But with an L1, most people report that the average is 6.5-6.8kWh. The reason L1 is higher than L2 is due to less conversion efficiency and a longer period of charge period (6 hrs for L1 vs 2 hr for L2) using fans and monitors for the charging.

    The data and graph below are my own record on my 2021 PP for the monthly average of kWh of electricity drawn from the wall for a full charge. The number of kWh is extrapolated for 100% even when only partial SoC was charged. In fact, the partial charge extrapolated for 100% is more consistent than using the "real" 100% full charge since you can not assess the amount of SoC % used after the EV range is depleted. My 13 months average for a full charge is 6.67kWh.

    Also, the use of "battery heater", "battery cooler", and "climate preconditioning" all use the traction battery kWh and increase the total kWh drawn from the wall but they do not end up stored in the traction battery when you unplug. In my record below, the Dec average was 7.22kWh which is higher than any other month. This is due to the fact that I had the "traction battery heater" function turned on. For subsequent months, I turned off the "battery heater" function and the number became consistent. I have never used the climate pre-conditioning or battery cooler functions.

    There is some conversion loss, so not all the kWh from the wall ends up being used for the traction of the car. My estimation is that ~85% of the L1 wall charge or 5.65kWh (6.65kWhx85%) total is actually used for the EV mode portion of the traction SoC.

    upload_2022-8-28_10-48-0.png
     
    #5 Salamander_King, Aug 28, 2022
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  6. davidewart45

    davidewart45 Junior Member

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    Thanks for all of the above responses. Given all the variables you all have pointed out, I can see that there is no precise "Full Charge kWh" figure. My second charge today was 6.34kWh.
    But even given all the variables, I think it would be helpful if Toyota would say somewhere that is easily discoverable, something like "When fully charged, EV mode will use X kWh (or X %) of the traction battery's 8.8kWh capacity." Or.
     
    #6 davidewart45, Aug 28, 2022
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