Technical review requested

Discussion in 'Clarity' started by insightman, Sep 13, 2018.

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  1. insightman

    insightman Well-Known Member Subscriber

    I'm preparing a couple of boards to display next to my Clarity PHEV at the National Electric Drive Week event in Ann Arbor this Sunday. I would appreciate it if the technical gurus on this forum would take a look at my Clarity Driving Mode Summary board and tell me what corrections I need to make or what I could do to improve the diagrams. The top diagram came from the paper written by the 3 Honda engineers describing the first Accord Plug-In Hybrid. The original i-MMD diagram I modified 6 times came from Car & Driver. Thank you.

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  3. Sandroad

    Sandroad Well-Known Member

    Nice! In the top matrix, the battery is highlighted red as charging in engine drive mode and there is a parenthetical (charge) in the mode box of that column. That right? It seems to conflict with the diagrams below.

    When you are at the event talking with folks, be sure to emphasize that it’s perfectly ok to just drive and enjoy the car; you don’t have to constantly manage all the power flow detail yourself to have a great driving experience. ;)
    K8QM likes this.
  4. V8Power

    V8Power Active Member

    Very slick diagrams. I love your commitment to educate people.

    I would say that the top diagram does not reflect the typical driving cycle because although the Accord shares the same core system, the PHEV driving cycle and hybrid experience is very different. With our bigger battery, the car stays in EV mode a lot and the ICE plays a secondary or even auxiliary “back-up” role in day to day shorter distance driving so the diagram shows much complex interaction between EV and ICE of typical cycle for the Clarity isn’t a good reflection of typical if we’re running with a charged battery after plugging in. For example, after 2 months of ownership commuting and stuff around town within battery range, we have been on electric 100% so the diagram would look really simple and the ICE has been our back-up generator range extender sitting idle. The diagram overcomplicates the reality of living with the Clarity I think. If I had to sum it up for newbies I’d say:
    1. In EV range regular driving it acts like a pure electric car
    2. Long distance regular driving: the ICE will automatically kick in when the battery runs out.
    3. If you press the accelerator very hard the ICE will turn on giving additional electric energy to the electric motor to boost acceleration.
    4. There are manual override modes (HV, sport) to preserve/charge the battery while driving and make response more spirited, these are optional.

    The way I explain to most folks who are new to all this or not technical, is that it’s essentially an electric car with a gas engine as back-up generator so there’s no typical car transmission and no range anxiety.
  5. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    You made those diagrams yourself? Awesome! You have a great talent for graphically presenting technical data in a very clear manner. I'm envious of your talent, sir!

    I am not qualified to critique the technical aspects, but as a matter of labeling, I suggest adding the words "ENGAGED" or "DISENGAGED" where you have the label "ENGINE DRIVE CLUTCH", to read "ENGINE DRIVE CLUTCH ENGAGED" or "ENGINE DRIVE CLUTCH DISENGAGED". I'd also eliminate the green font in the one diagram where it's engaged; that just makes it harder to read.

  6. KentuckyKen

    KentuckyKen Well-Known Member

    Great diagrams @insightman!
    Any technophile at the event will get all the info they need and I'm sure you’ll simplify it for the general public in your Q&A conversations.

    One comment:
    I don’t know if it’s possible or exactly how to show it graphically, but in HV mode all the power flows cycle on and off. It doesn’t show that some times the ICE couples mechanically, sometimes the battery is being charged, some times the battery only is supplying power and some times power is being supplied by both battery and ICE/generator.
    Please consider this a very, very minor critique.
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  8. lanb

    lanb Active Member

    I think Honda should have labeled the 3 modes as

    "Short/Med trip", "Long trip", "Fast trip"

    That is how I view Econ/HV/Sport modes as :)
  9. ab13

    ab13 Active Member

    The diagrams could be adjusted to match Honda's diagrams. These are the videos for the immd of the previous Accord design. The output gear is turned by the EV motor gear along with the clutched in engine gear. The Car and Driver diagram is slightly different.

    Here are some nice pictures.
  10. insightman

    insightman Well-Known Member Subscriber

    Thanks to all for your suggestions. Now I'll blather on about my revised technical presentation.

    First, I should have said that I expect two possible audiences at the National Electric Drive Week event. First, there will be the owners of the other plug-in cars being exhibited at the event. The board presenting the chart and diagrams illustrating the operation of the Clarity Plug-In Hybrid’s i-MMD system are mostly for them, but some technically oriented visitors may also be interested in this information.

    The less-technical board will have two audiences: the owners of the other plug-in cars and the new-to-plug-in-cars visitors to the event. This board will list the features of the largely unknown Clarity Plug-In Hybrid and describe how easily people can take advantage of its EV drive capabilities to both save gas and drive a more enjoyable car. Another part of the second board will compare the Clarity Plug-In Hybrid to the Volt, Prius Prime, and, of course, the always-in-the-news Tesla Model 3 (even though it’s not a hybrid car). I'm hoping to get a rise out of the non-Clarity plug-in owners by denigrating their cars to the Clarity's advantage.

    Second, I must say I was surprised no one commented on my last diagram, Zero-Regen Engine Braking. This topic has been of special interest to me because of the people on this forum reporting their cars starting the engine upon deceleration when the battery is fully charged. I couldn’t think of a good way to graphically illustrate my theory about the starter motor/generator reversed to use up excess electricity by trying to slow down the engine. So I decided to put the word “FIGHT!” in the arrow connecting the starter motor/generator and the engine. If nothing else, it will spark some conversation between me and a Volt owner while we’re standing around waiting for any non-owner visitors to show up.

    @Sandroad pointed out that the Mode Transitions chart at the top shows charging occurring in Engine Drive mode, but my diagram of Engine Drive mode shows power coming from the battery to the traction motor. I found this article that directly addresses the misconceptions of Engine Drive mode. It points out that the SAE paper by the 3 Honda engineers indicates that both battery charging and assisting can take place in Engine Drive mode:

    > Although “Engine Drive” mode is mainly utilized during high speed cruise,….
    > engine load adjustment by charging or discharging the high voltage
    > battery is also performed in this mode to fix engine operating points in
    > highly efficient area…

    So I changed the Mode Transitions chart to include a segment where battery assist is taking place in Engine Drive mode. Then I changed the Engine Drive diagram by making the arrow between the traction motor and the battery bidirectional.

    @V8Power commented that the chart titled “Clarity PHEV Driving Mode Transition of Typical Driving Cycle” wasn’t an accurate representation because the Clarity PHEV stays in EV Drive mode much more of the time than the 2014 Accord Hybrid for which this chart was originally prepared. Rather than expanding the width of the EV segments (which would make the chart too wide), I simply changed the title to “Clarity Plug-In Hybrid Driving Cycle Mode Transitions.” The important thing about the chart is to illustrate the ways the battery, engine, motor, and generator interact to maximize efficiency.

    @V8Power’s suggestion to explain the Clarity Plug-In Hybrid as essentially an electric car with a gas engine as back-up generator to eliminate range anxiety is a good one and I will work it into the less-technical board I plan to bring to the National Electric Drive Week event.

    @Pushmi-Pullyu made a good suggestion to abandon the hard-to-read green text in the diagram for Engine Drive Mode and also to indicate in the label of each diagram whether the Engine Drive clutch was engaged or disengaged. I incorporated those suggestions in all the mode diagrams. I also indicated when the engine is running and when it is off.

    The always helpful @KentuckyKen noted that the Mode Transition chart does not graphically illustrate how in HV mode all the power flows cycle on and off. Like the authors of the original chart, I couldn’t figure out a graphical way to make this clear. However, the boxes at the top of the chart indicate that the car cycles intermittently through different modes while cruising.

    Then came @ab13’s suggestion that I adjust the diagrams to match Honda’s diagrams from one of their videos that explains the i-MMD system. It was a good suggestion to base the diagrams on info directly from Honda instead of Car & Driver’s interpretation. All the diagrams have been changed to use Honda’s gearing and component arrangement.

    No one complained about my theory that the starter motor/generator is fighting the engine to provide pseudo engine-braking when the battery is fully charged, so I kept that--and even added two more exclamation marks!!!

    I extend my grateful thanks to all of you who helped me improve my presentation! I’ll submit my other board when I finish it, but after spending so much time on the mode diagrams, I’ll be lucky to get that board finished before the Sunday event.

    If there's anything really wrong with the revised chart and diagrams, please tell me, but I'm running out of time to make the less-technical board listing the virtues of the Clarity vs. the other plug-in cars, so I won't be able to make any major changes like the one to mimic Honda's diagram.

    Last edited: Sep 15, 2018
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  11. JCEV

    JCEV Active Member

    It would be also useful to indicate unofficial HP numbers . Fore example EV drive mode rumours are 121-140(not sure) hp, Hybrid drive 181 and engine drive 232hp
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  13. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    I see you completely re-did the clutch part of the diagrams, showing a much clearer separation of the clutch plates when the clutch is disengaged, and you also used red to indicate a power flow when the clutch is engaged.

    Well done, sir! I think these changes help a great deal in showing what's happening using graphics, with less reliance on explanatory text... which obviously was your goal, and it's a goal at which you have succeeded admirably. Your screen name, Insightman, appears to be well-chosen... whether or not you drive a Honda Insight! :)

  14. insightman

    insightman Well-Known Member Subscriber

    Another great (and easy to implement) suggestion! Honda claims 212 hp max for the Clarity Plug-In Hybrid (and, coincidentally, also for the new Accord Hybrid, even though it has a more powerful engine). Honda says that EV Drive mode produces up to 121 hp and Hybrid Drive mode produces up to 181 hp, so by default the only other drive mode, Engine Drive mode, must be capable of 212 hp. It makes sense that the max isn't the 284-hp sum of the 103-hp engine and the 181-hp motor because some of the engine power is going to the traction motor, instead of the wheels.

    As the article I linked earlier states, under heavy acceleration, the Clarity Plug-In Hybrid switches to Hybrid Drive mode. Does that mean the 212 hp is available only if you coax the car into Engine Drive mode and then slowly apply more gas, er, accelerator? Oh well, I have to put that 212-hp number into the diagrams somewhere, so I'm putting it into the 3rd remaining Drive diagram, Engine Drive (it would seem unsexy if the highest horsepower happens in the workhorse HV CHARGE Mode because then the full 212 hp isn't getting to the road).

  15. ab13

    ab13 Active Member

    You may want to note the torque on at least one of the diagrams.
  16. insightman

    insightman Well-Known Member Subscriber

    I know the traction motor can supply up to 232 lb-ft of torque, however, I've never verified that the full 232 lb-ft is available in EV Drive mode, when the horsepower is limited to 121. Unlike the horsepower ratings, Honda's never specified in which configurations the full torque is available.

    Now I'm wondering if flooring the accelerator in HV CHARGE Mode actually results in power coming from the battery to the traction motor. If it doesn't then I should delete the arrow from the battery to the traction motor in that diagram.
  17. ab13

    ab13 Active Member

    The torque is specified down to 0 rpm, so it seems at initial start is available, maybe just note it but not in a specific diagram.

    "232 lb-ft @ 0-2000 rpm"
  18. insightman

    insightman Well-Known Member Subscriber

    I've added in large text below the top chart: "Note: Traction motor produces 232 lb-ft of torque starting at 0 rpm." I don't know more than that, so that's as specific as I'll be. It gets that big, wonderful number into play, for which I thank you.
  19. insightman

    insightman Well-Known Member Subscriber

    Thinking back, posters have reported acceptable performance in HV CHARGE Mode, so I'm assuming the traction motor must be receiving more power than just that generated by the 103-hp engine. I'll leave the arrow from the battery to the traction motor in that diagram.
  20. ab13

    ab13 Active Member

    This would be an interesting case to put on the dynomometer.
  21. JCEV

    JCEV Active Member

    I think in charge mode the generator is producing excess power, enough to drive the traction motor with the excess going to the battery. Does anyone know what is the maximum power\energy that can be generated by the ICE ?
  22. insightman

    insightman Well-Known Member Subscriber

    Here's the final version of the Clarity PHEV technical presentation I'll be displaying tomorrow at the National Drive Electric Week event in Ann Arbor. Thanks to all who assisted me with good criticism and great ideas.

    Oak Hill Dan likes this.
  23. insightman

    insightman Well-Known Member Subscriber

    Here's the final version of the Clarity PHEV promotional presentation I'll be displaying tomorrow at the National Drive Electric Week event in Ann Arbor. I worked too long on the technical presentation and had to slap this one together in a few hours. It has a dual purpose: To tweak the Tesla owners who will greatly outnumber me at the event, and to provide Clarity-slanted educational information for the 5 or 6 non-owner "attendees" who might wander into our midst from the Whole Foods store whose parking lot we'll be occupying. You can offer criticisms, comments, and better ideas, but it's too late to make changes to the 20" x 30" poster board I just finished pasting together to go with the 20" x 30" technical board I finished pasting together an hour earlier. I dared to look at it before posting and saw two errors that took a half-hour to fix. I apologize if the text is too small to read. I'm going to bed.
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