True MPG of Clarity PHEV fully charged

Discussion in 'Clarity' started by geminiwave, Aug 7, 2018.

  1. 2002

    2002 Well-Known Member

    Sorry I can be a little dense at times but I'm still not clear. "EV Mode switched to HV Mode" sounds to me like that would be when you let the computer handle things because the computer defaults to starting out in EV mode then it automatically switches to HV mode. But you say that's the one where you try and manage things.

    Just to help me, instead of names I will list a few scenarios, based somewhat on assumptions for example I will assume that since the trip is 60 miles each way, the outbound leg is probably longer than your EV range since much of that is presumably high speed where EV range gets used up relatively quickly. And I will have to assume that outside temperature conditions are the same or similar as is AC usage.

    Scenario A: Start with a full charge and a full tank of gas. Allow the computer to manage the entire trip. It will start out in EV, then sometime before reaching your destination EV range goes to 0 and HV mode is automatically activated (you will be in HV mode at this point even though the HV indicator won't appear on the display). You will then be in HV mode for the remainder of the outbound trip as well as the entire return trip. You end the trip with 0 EV range and having used X gallons of gas (this means the trip must end at the gas station not your house so that you can measure the actual amount of the gas used).

    Scenario B: Start with a full charge and a full tank of gas. Prior to starting out switch to HV mode and remain in HV mode for the entire outbound trip of 60 miles. Prior to departing for the return trip switch to HV mode (otherwise it would default to EV). At some point on the return trip, making sure that your EV range is less than the distance to "home" (actually the gas station) turn off HV and the EV range will start going down and should get to 0 before you get to the gas station, at which point it will automatically switch to HV for the remainder of the trip. If there is more than 0 EV range left when you reach the gas station then the test is invalidated and cannot be compared to scenario A. You end the trip at the gas station with 0 EV range having used Y gallons of gas.

    Scenario C: Since your return leg is slightly more than your EV range this is probably a little easier than scenario B and should have similar results. Start with a full charge and a full tank of gas. Prior to starting out switch to HV mode and remain in HV mode for the entire outbound trip of 60 miles. When starting out for the return trip of 60 miles allow it to default to EV. At some point towards the end of the return trip EV range will become 0 and HV mode will be automatically activated (even though it doesn't show it on the display). You end the trip at the gas station having used Z gallons of gas.

    What we are interested in is what are the resulting values for X, Y and Z, i.e. how much gasoline is used in the different scenarios. If you aren't ending the trip at a gas station and measuring the gas used and are instead going by what the trip mpg is showing that is not accurate data. And if you end any test with more than 0 EV range then it is not a valid comparison to a trip which has remaining EV range.
    insightman likes this.
  2. KentuckyKen

    KentuckyKen Well-Known Member

    IMHO, MPG is meaningless unless you account for both gasoline AND kWhs used. Otherwise it’s an apples and oranges type comparison. Even doing an entire trip in HV will use some kWhs.
    However when I have done this, the small amount of electricity used only reduced my MPG by 1.
    insightman and Louis Nisenbaum like this.
  3. 2002

    2002 Well-Known Member

    I think you might be talking about something different than the current discussion about whether it is more efficient to allow the system to choose when to use EV miles.

    If you are trying to determine true MPG then yes by definition that means the power for all of the miles driven had to come from gasoline. That type of test requires starting with 0 EV range. Yes the battery still has some charge even at 0 EV range but as long as the trip begins and ends with 0 EV range then all of the power that propelled those miles came from gasoline, none of it came from the grid. To be more precise the app will show SOC at 0 EV range as being typically 8-10% so if you started with say 9% and ended with 8% you would need to factor in that small amount of electricity used. You could also pretty much wash it out by making the test long enough like several hundred miles but most of us would probably go through withdrawals if we went that long without being able to run EV :D. Probably better is to simply repeat the test multiple times, standard for tests is to run the identical test at least three times then divide by three for the average. More tests are even better but three is considered adequate in many situations, as long as you can keep variables like temperature as close as possible.

    The current discussion on the other hand is about starting with a full charge and whether it is more efficient to use the EV miles on surface street or highway. The actual question was whether to allow the computer to make this decision or try and manage it yourself. But that question is too vague because it depends on the route. The computer has no idea what the route will be (regardless of Nav usage) it just uses up EV until it is gone so it will essentially be random and so the route itself will determine how much of those miles will be on surface street vs. highway. But still it's possible to compare by running the same route multiple times, in some cases starting out EV and staying EV until it runs out and other trips managed by the driver when to use the EV range. As long as the trips being compared are the identical route and each starts with 100% SOC and ends with 0 miles (again about 8-10% SOC) then the actual gas used can be compared to determine which method uses more gas. Of course temperature has to be factored in, wet or dry roads, the slight SOC difference starting and ending, etc. so again ideally multiple trips are made so that trips with similar conditions can be compared. Also when filling the gas tank at the end of each trip there is a variable if the pump doesn't cut off at exactly the same time, but again multiple tests should help wash that out.
  4. KentuckyKen

    KentuckyKen Well-Known Member

    I think we are saying the same thing in that gas and SOC need to be accounted for in determining efficiency no matter what the mode.

    “Don’t try this at home, I’m a professional thread drifter.”
    Apologies for going off topic.
    2002 likes this.
  5. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Thank you sir!

    I get sooooooo tired of Volt drivers bragging about their "MPG", when they really mean the number of miles they got on X gallons of gas PLUS an unreported and unacknowledged number of kWh of electricity. They are using the term "MPG" in a manner that makes it meaningless.

    The term MPG, or "Miles Per Gallon", means miles powered by gasoline (or other fuel) ONLY. Not blended use of gasoline power and electric power.

    For PHEVs like the Volt and the Clarity PHEV, a separate count should be made of gas-powered miles and electric-powered miles. As I understand it from what I've read (I've never driven a Volt), the statistics reported by the app does count gallons of gas and kWh of electricity separately, but sadly it seems that most Volt owners bragging about their fuel economy online report only the gas they used, and ignore the kWh of electricity used, in driving a certain number of miles.

    As I understand it from reading a lot of posts about the Clarity PHEV, it blends use of gasoline and electricity in a more mixed manner than the Volt does. The Volt will never will fire up the gas-powered generator unless (1) the battery pack falls to... I think it's ~30% capacity? ...or (2) the car is so cold that it needs to fire up the gas motor to generate heat to warm the battery pack up to efficient operating temperature.

    Given that the Clarity PHEV (if my understanding is correct) blends use of electric power and gasoline power more than the Volt does, even when the Clarity PHEV's battery pack is fully charged, it is harder (or, based on what is reported just in this thread, nigh-impossible) to separate miles powered by gasoline from miles powered by kWh of electric energy which came from a plug.
    Last edited: Jul 14, 2019
    2002 likes this.
  6. RobinBrain

    RobinBrain Member

    I log all my fuel ups, and my charges, how would I used these two numbers to determine my MPG's? Do I convert the KWh to Gallons of gasoline and divide the total mileage by that number?
  7. fotomoto

    fotomoto Active Member

  8. KentuckyKen

    KentuckyKen Well-Known Member

    Here are some quotes from other threads that I have saved and use in my calculations.

    1MPGe = 1 mile /33.3kWh
    =.02967 miles/kWh
    Based on 33.3kWh in a gal of gas (I think 33.7 is the correct # to use)

    EPA says Clarity uses 33.1 kWH/100 miles or 0.331 kWh/mile
    And rates it at 110 MPGe
    But 1 gal gas technically has 34.01 kWh
    EPA uses 33.7 kWh/gal for BEV, PHEV

    I've not seen anything I trust, but you can figure it out from information on the new car sticker. The sticker indicates the car gets 110 MPGe. MPGe is miles/KWh*33.7. If you divide 110 by 33.7 you get 3.264 which is the distance in miles Honda thinks the car will get per KWH. If you divide 47 by 3.264 you get 14.4 which is the usable KWH of the battery. That ends up being 84.7% of the 17 KWH battery.

    There is a lot of information at battery university which explains why Lithium Ion batteries are not fully charged or discharged.
  9. Thevenin

    Thevenin Member

    I have been tracking my Clarity's fuel and electricity consumption religiously, logging electric and gasoline miles separately.

    On electricity (charging at 120V, w/10AWG 25ft ext. cable)
    90% Highway (72mph, 75°F): 2.9mi/kWh
    Backroads (35-45mph, 75°F): 3.8mi/kWh

    On gasoline (0 EV miles remaining, SoC stable at 10%)
    90% Highway (72mph, 75°F): 45.2 mpg
    Backroads (35-45mph, 75°F): Insufficient data. >50mpg.
    MajorAward likes this.
  10. d99

    d99 New Member

    I was told the technician cannot print anything out. He did say the battery capacity was 85% from information on his screen. Can someone tell me what that indicates? I also opened a case with American Honda, an enlightening and disappointing experience. One would think that when a case is opened, someone actually looks into the problem. NO! Nothing actually happens. Would you believe they actually say that! You speak to someone who takes down the details, and they try to say soothing words, but admit they are not at all technical. What I think happens is if enough people complain, it might eventually trigger an investigation.

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