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Prius Prime XSE/XSE Premium dismal BEV range

Discussion in 'Gen 5 Prius Main Forum' started by Gokhan, Jul 31, 2023.

  1. Gokhan

    Gokhan Senior Member

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    It should be (1) at the battery and (2) reported with driver bias (like mostly city driving), as it corresponds to 33.705 × 4.3 = 145 mpge, which is quite higher than the EPA mpge at the wall. Most test results showed that Tesla Model 3 cannot meet the EPA mpge figures. So, it should be around 120 mpg average, which is 3.6 mi/kWh at the wall.
     
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  2. tovli

    tovli 2023 Prius Prime replaced 09 Prius

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    That 4.3 mi/kWh figure exactly matches my average car reported efficiency in 1119 EV miles in 2023 Prius Prime XSE under similar driving approach and prior vehicle (2009 Prius for 14 years).
     
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  3. jackalope

    jackalope Member

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    This is with a ~50/50 mix of highway and city driving including several long, overnight trips. Just like in the Prius, it is pretty easy to beat the EPA estimates, especially with the base model with a single motor. We don't drive conservatively and just enjoy the car, especially since energy is relatively inexpensive, even here in CT where we pay more than average for electricity (~$0.21 / kWh). I don't think the car's measurement includes the non-driving energy use such as pre-heating/cooling, though I am not certain.

    Over the 6 months and 7,500 miles we have owned the car, the average has been pretty steady. We had some hot summer driving, but only caught the tail end of the winter. I will see how it averages over the year to get a full year picture.

    I think like the Prius, it is easy to get below, at, or above EPA figures since your right (or left) foot has a large influence on efficiency.
     
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  4. jackalope

    jackalope Member

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  5. Gokhan

    Gokhan Senior Member

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    Yeah, in my Gen 4 Prius Prime, I can almost get 30 miles (146 mppge on the wall watt–hour meter) on the freeway while the EPA mixed-driving range is 25 miles (133 mpge). 38 miles (202 mpge) is not difficult in gentle city driving. If you drive hard, 25 miles (133 mpge) is probably about right in mixed driving.
     
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  6. tovli

    tovli 2023 Prius Prime replaced 09 Prius

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    Can you explain what "mpge on the wall watt-hour meter" means?
     
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  7. otatrant

    otatrant Active Member

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    33.7 multiplied by miles per kWh from the wall reading.

    33.7 kWh in one gallon of gas.

    That is my understanding.
     
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  8. tovli

    tovli 2023 Prius Prime replaced 09 Prius

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    Huh? Look I understand the mpg energy equivalency, but what does it have to do with the wall power?

    Everyone’s EVSE is in the middle so there is no such thing as “4.3 mi/kWh at the car, is 100/4.3 divided by 33.7 “miles per gallon equivalent at the wall”. I don’t understand the meaning of “gallons at the wall”

    My level 1 charging “at the wall” places a 35% tax on my at the car 4.3 mi/kWh turning it into 3.2 mi/kWh “at the wall”.
     
  9. otatrant

    otatrant Active Member

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    That is confusing to me.
    What would that calculate?

    You obviously have more time driving under you belt and making these calculations just trying to understand what you are saying.
     
  10. Gokhan

    Gokhan Senior Member

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    EPA mpge values correspond to the BEV range of the vehicle divided by kWh recorded by the wall watt–hour meter during Level-2 (240-V) charging.

    33.705 kWh = 1 EPA gallon equivalent (ge)

    Therefore:

    EPA mi/ge (mpge) = 33.705 kWh/ge × EPA BEV range (mi) / Level-2 kWh used
     
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  11. tovli

    tovli 2023 Prius Prime replaced 09 Prius

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    I am saying I am confused
     
  12. Gokhan

    Gokhan Senior Member

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    I don't know how much is lost in the charger, but the difference between Level-1 and Level-2 charging kWh is no more than 8% for Gen 4 Prius Prime.
     
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  13. Gwyd

    Gwyd Member

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    I've this entire thread and understood about 60% of it - but I think "gallons at the wall" is a calculation of what it costs (in electricity) to charge the car and convert that number to what it costs to buy an equivalent number of miles in gas.

    So 2 hours of charging costs $2 and gives you 20 miles of battery driving
    Driving on the gas engine for 20 miles would cost you $5 in gasoline
    (wildly wrong numbers, just an example people)

    The calculation they're using is a conversion for that to make the miles driven on electric have a direct relationship to the miles per gallon we normally refer to on gas engines.

    At least that's what I understand it to be - someone please correct me (in normal language without acronyms or equations) if I've gotten it wrong.
     
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  14. Gokhan

    Gokhan Senior Member

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    No, it is not. ;)

    It has nothing to do with cost. kWh is an energy unit like BTU, not necessarily an electricity unit. 1 gallon of gas, when it burns, releases 33.705 kWh of energy. That's all it means—it is nothing but the energy content of 1 gallon of gas. You can look up the energy content of wood, coal, etc. in Wikipedia.

    Heat engines like internal combustion engines typically have less than 50% thermodynamic efficiency. That's why the BEV mpge numbers are more than twice the internal-combustion-engine-vehicle mpg numbers.

    For examplen in Iran, where gas is practically free (like a penny a gallon), you still have the same mpge numbers, as the conversion is for the energy content, not the cost.
     
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  15. hill

    hill High Fiber Member

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    Speaking of "no it's not" .... Iran pays roughly 15,000 iranian rial (about 36¢) per liter .... of which it takes over 3¾ liters to make a gallon.
    IE; you're off by a factor of over 10
    ;)
    Factor in average income in a big city like Tehran ... the income expense would feel like one was paying between $3 & $4 USD per gallon.
    .
     
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  16. Trollbait

    Trollbait It's a D&D thing

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    EPA fuel efficiency calculations are based on the amount of fuel that went into the car. That means from the pump for the liquid ones, and from the outlet for electricity. For a plug in, that means the official mpge figure is including the charging losses. Tracking efficiency from what the car reports it used will yield a better result, as it doesn't include those losses.

    Which is better for you to track depends on your goals. Wanting to know how efficiently you are driving, and trying to improve that, the car reported, from the battery is fine. Want to track more, like costs or comparing directly to EPA, you need from the outlet. The consumption the EVSE reports is good enough for most. There are options for when it isn't.

    Are you charging with the supplied EVSE from a 15 amp outlet? Faster charging can reduce the losses if that is a desire.
     
    #76 Trollbait, Sep 18, 2023
    Last edited: Sep 18, 2023
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  17. Gokhan

    Gokhan Senior Member

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    Hmm, OK, penny is an exaggeration, but your number doesn't sound right.

    OK, so, it is 11¢ a gallon in Iran and 1.5¢ a gallon in Venezuela.

    Iran gasoline prices, 11-Sep-2023 | GlobalPetrolPrices.com
     
    #77 Gokhan, Sep 18, 2023
    Last edited by a moderator: Sep 22, 2023
  18. Nntw

    Nntw Active Member

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    Mine says 19%of charge used for 26km.

    Running off the top of the tank, er, battery
     
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  19. Gwyd

    Gwyd Member

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    That is a much better explanation, thank you!

    If I understand, you *could* calculate an electricity vs gas cost comparison if you wanted to, but you're really looking for the cars energy input efficiency.
     
  20. jackalope

    jackalope Member

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    When looking at EV range (OP's question) it seems to make the most sense to look at the efficiency as reported by the car and not worry about charging losses.

    When considering the costs then charging losses make more sense. This gets extra complicated if one charges at places with different prices.
     
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