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How many kWh of 8.8kWh battery is usable?

Discussion in 'Prime Main Forum (2017-2022)' started by luckie, Dec 12, 2021.

  1. luckie

    luckie Junior Member

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    What is the latest info for recent model year Prius Primes regarding what portion of the 8.8kWh battery is usable? I read some Prius Chat threads from a number of years back, including those way back when it was the Plug-in Prius PIP. I'm predicting it appears maybe 75% of the battery is usable and thus 25% is buffer/protection for battery cells. But curious if some folks know more precisely and for recent model years. Thanks. Doug
     
  2. Salamander_King

    Salamander_King Senior Member

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    The precise number is still not known. Even empirical number varies from person to person. That being said, from the wall, anywhere from 5.9kWh to 6.7kWh is needed to fully charge the battery. The usable portion including the HV mode portion is about 6.6kWh, which leaves the EV mode portion of the traction battery ~66% of full capacity (8.79kWh) or ~5.8kWh.
     
    #2 Salamander_King, Dec 12, 2021
    Last edited: Dec 12, 2021
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  3. 0ddj0b

    0ddj0b New Member

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    my experience has been:
    top 25% cannot be topped up by "CHG mode"
    bottom 25% used as reserve, cannot dip into

    and then you're left with 50% battery to charge up and deplete at will.

    If you are topping up at a charging station regularly then this is less of a problem
     
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  4. Salamander_King

    Salamander_King Senior Member

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    CHG mode only lets you charge the traction battery up to 80% SOC on the car's MID display. That is only 70% actual SOC. The data below shows the SOC (%) displayed on the MID vs the actual SOC (%) reported by Hybrid Assistance App from ECU via OBDII. It was taken from my 2017 PP, but this should be very similar for the newer PPs.

    As you can see, the 100% SOC on MID is actually 80-85% and --% on MID when EV range is depleted is somewhere around 10-15% real SOC. Anything below this lower threshold is used strictly by the HV mode. During the HV mode, the real SOC can dip as low as ~7%, but that is rare. Thus it was concluded that the top reserve is ~15% and the bottom reserve is ~10%, leaving ~75% total of usable portion for the operation (this includes both EV and HV portion). Still, the question remains where the precise EV/HV transition occurs. If you take the single point data from the graph below as one example, then it is at ~15% SOC, but I think this number varies somewhat by other factors.

    upload_2021-12-13_8-14-37.png
     
  5. luckie

    luckie Junior Member

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    Thanks for the prompt and helpful responses. It makes sense that Toyota would protect the traction battery with a good buffer. Chevrolet did the same for their Chevy Volt battery.

    This also helps clarify that the movie (links to "The Car Care Nut" video from Fall 2020 peppered around posts on Prius Chat) of a mechanic sharing their experience with Prius Primes is, as one might expect, just one persons ideas. In the video he shares the point that one should rarely let the Prius Prime battery remain in a 100% state of charge (via the guess o meter on the MID display) because that would harm the battery ("charge to 100% in the morning and drive soon after charging..."). While the sentiment is valid for Lithium batteries and some EVs that provide the driver with access to nearly 100% of the battery (e.g. Tesla), it's good to know that in the case of the Prius Prime the customer is not permitted to actually charge the battery past ~85%. And 85% provides very generous protection for the battery longevity.

    Related question, in the video this mechanic shared that he had customers who never ran the gasoline engine for over a year, simply used electric EV mode, which could certainly happen, and that stale gas (and the alcohol in the fuel in particular) really harmed the car and led to expensive repairs. In a similar car to the PP, the Chevy Volt, once and awhile the software would automatically alert the driver that it was going to turn on the gasoline engine to perform a "maintenance mode" to move fluids etc, does the Toyota Prius Prime do a similar automatic use of the HV system if months have passed without using the gasoline engine?
     
  6. Salamander_King

    Salamander_King Senior Member

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    I drive my PP on HV often enough, so I have never seen the warning comes up on my car, but PP is suppose to be equipped with such a warning. See the note from the manual below.

    upload_2021-12-14_10-43-11.png
     
  7. DOHCtor

    DOHCtor Member

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    My guess would be about 70\75% as the longest charge i ever did added something like 6.3Kwh to that 8.8Kwh battery.. :)
     
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  8. Tideland Prius

    Tideland Prius Moderator of the North
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    Supposedly but I did an experiment when the car was new and I drove 78 days without the engine coming on.

    Engine Maintenance Mode | Page 3 | PriusChat
     
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  9. luckie

    luckie Junior Member

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    Thanks for that info, so at the very least the PP will alert you if it predicts the fuel is getting stale. Good to know. I think I only once saw a warning related to stale gasoline when owning my Gen 1 Chevy Volt. In the Spring of 2021 after the first winter of the pandemic. Since I live in Michigan I do not expect stale gasoline will frequently become a problem if for no reason other then heating the car in winter. But as the pandemic goes on, and if Omicron is an escape variant as it appears to be, might happen.
     
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  10. luckie

    luckie Junior Member

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    Wow, great experiment, much respect. Hmmm... I regularly saw alerts saying something like "Maintenance Mode, can we do it now?" on my Gen 1 Chevy Volt. It, of course had a 16kWh battery, which got me 50 electric miles each day and thus made it even easier to never use gas. So, the PP may not worry as much as the Volt did about Maintenance Mode, for me in Michigan, while in winter the heater will likely take care of circulating fluids and consuming gas, but in the late Spring-Summer-Fall stretch I should go on a few road trips to see family. :)
     
  11. Tideland Prius

    Tideland Prius Moderator of the North
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    Yeah that’s why we wanted to see if the Prime had the same engine maintenance mode.

    Also, I haven’t seen the “Add Fuel” light yet even after a year. I think some have gone nearly a year and a half before seeing the “Add Fuel” where the car determined that the gas is stale.