Gas to electricity

Discussion in 'Clarity' started by Trabman, Apr 14, 2018.

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  1. Trabman

    Trabman New Member

    Has anybody figure how much gas is required to charge the lithium battery to 50% (8.5kwh) using HV Charge?
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  3. jdonalds

    jdonalds Well-Known Member

    What seems to happen is, at 75mph, the car goes from about 40'ish mpg to 30'ish mpg in HV mode when Charge mode is turned on. Then it takes about 1/2 hour to reach max charge which is said to be 58%. If I calculate this correctly that means for 37.5 miles without Charge mode would use 0.94 gallons while Charge mode would use 1.25 gallons.

    Putting a cost in the calculations I'll use $3/gallon (it's higher than that in CA today).

    For 37.5 miles no Charge mode = $2.81
    For 37.5 miles with Charge mode = $3.75
    Difference = $0.94

    Most of us think we get to use 14KWh of the 17KWh battery. So 58% of that is 8.12KWh that would be charged in Charge mode.

    So to charge 8.12KW would cost $0.94 or $0.12/KWh. Not bad if my calculations are correct. Our grid electricity cost is $0.15/KWh.

    I'd like these calculations to be correct so if anyone sees errors please post them.
    MarkClarity and AlanSqB like this.
  4. BlueHeron55

    BlueHeron55 New Member

    Thank you for these very helpful calcuations. I was wondering about the same thing, but your math helped to clarify. One question that I had... when using re-charge in HV mode, how does it affect driving? Does it put more strain on the engine? Reduce power/speed? Is it a noticeable effect? I’m considering purchase of a Clairty, but wanted to get a sense of how the highway/regen performance is.

    Sent from my iPad using Inside EVs
  5. kkiran

    kkiran Member

    Nice analysis! It is kinda difficult to get to accurate numbers without Honda providing hard numbers for electric and gas miles. It shouldn’t be difficult. I will try to validate this on my first long trip. We have a CRV but I want to bank on this generator tech for more electric miles.

    Sent from my iPhone using Inside EVs
  6. jdonalds

    jdonalds Well-Known Member

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  8. jdonalds

    jdonalds Well-Known Member

    Our only experience is a trip we took back in December when we purposely alternated between EV and Charge to see if it would result in higher mpg overall (inconclusive). The road was flat and speeds were 70-75 mph. There was no discernable effect on the driving characteristics of the car. Perhaps there might be some noticeable effect if Charge mode was used in a hilly area.

    I have used Charge mode a couple of times more recently, for brief periods, with no noticeable effect.
  9. Hi.Ho.Silver

    Hi.Ho.Silver Active Member

    Assuming your avg mpg estimates with and without HVCharge mode enabled are reasonably accurate this methodology can save significant gasoline on a trip.

    Here’s my calculation:
    The restored 58% charge will “carry you” 27 miles (.58 x 47 miles with a full charge). If you were in normal HV mode you would burn .68 gallons of gas over that 27 miles (27/40). At your $3/gallon (gas is a bit cheaper here in NC) that would be $2.04 you save against an investment of $0.94 or a net savings of $1.10. Almost sounds too good to be true but the math seems to be correct. Any thoughts.
  10. PHEV Newbie

    PHEV Newbie Well-Known Member

    That's really interesting. Nevertheless, I always switch to HV mode on sustained highway use because 1) You need to run the ICE not infrequently to keep all parts properly lubricated (might be less true with modern engines but the Clarity's 0W-20 motor oil is not going stay adhered as well); 2) High DoD or "depth of discharge" is a killer for battery life. Fast accelerations and high speeds are where DoD is greatest. The cost of replacing the battery will be many thousands so I'd like to keep the range as high as possible for as long as possible for my everyday use; 3) I like to keep a charge for EV use at the destination.

    BTW, no matter how little you use the ICE, you need to change the oil at least annually because of normal oil contamination and breakdown over time. That's the advice of consumer reports even as they advise you not to change it too often (putting an end to the 3 month/3,000 mile myth for ICE cars).
  11. Trabman

    Trabman New Member

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  13. Trabman

    Trabman New Member

    Wow! Thanks jdonalds for your reply and thoughtful calculation!
  14. Trabman

    Trabman New Member

    ....and everybody who has contributed to this thread!
  15. Atul Thakkar

    Atul Thakkar Active Member

    In Canada, gas prices is @ 5 + per gallon, and electicity cost in off peak time is 6.5c per kwh, so it would be different in Canada
  16. Tiralc II

    Tiralc II New Member

    Here is another view using the same numbers, $3 per gallon, 0.15 / kWh

    Convert "40ish" (40ish means +/- 25%) to 44 mpg and use 47 miles / 14 kWh (varies based on terrain, temperature, and speed).

    47 miles x .58 = 27 miles 14 kWh x .58 = 8.1 kWh 8.1 kWh x 0.15 = $1.22

    27 miles (from above) / 44 mpg = .61 gallon .61 gallon x $3 / gallon = $1.83

    To go 27 miles by EV costs about $1.22 To go 27 miles by gas costs about $1.83, or about $0.64 more on gas compared to EV.

    The reason the original conclusion is different is because of the "ish" factors. With gas prices relatively low, the differences are only in the tens of percent. By adding enough "ish" factors with +/- 10's of percent, any poster can make the numbers come out either way.

    It would be very difficult to verify these calculations by driving without significant effort. For example, it would take filling gas at just the right time, because we don't know how accurate or linear the gas gauge is. Also, the EV mpg varies widely with temperature and many other factors. It would take multiple trips in both directions (because net terrain gain or loss is different) at carefully controlled speed, to get measured numbers. Even wind (e.g. a head wind or tail wind) could throw the numbers off by a significant percent.
  17. Tiralc II

    Tiralc II New Member

    yes, I also understand that you are trying to "prove" that one can get lower operating cost by using gas to charge the battery. Here is why I think it would be very difficult to measure:

    First 10 runs (5 each direction) (record ambient temperature, road conditions, any strong winds and wind direction)
    Two bars EV “empty”, start at gas station, fill to auto click off (fill error unknown).
    Drive to nearby a highway, drive EV charge mode at a constant speed on until EV charging stops (record the number EV bars).
    Immediately exit highway, and refill to autoclick off, record gallons added.
    ->Repeat the process ten times, five from each gas station (five in one direction, five in the opposite direction), every time starting with full EV discharge.

    Second 10 runs (5 each direction) (record ambient temperature, road conditions, any strong winds and wind direction)
    Two bars EV “empty”, start at gas station, fill to auto click off (fill error unknown).
    Drive to nearby a highway, drive HV mode at the same constant speed.
    Immediately exit highway at the same exit and gas station as above, and refill to autoclick off, record gallons added.
    ->Repeat the process ten times, five from each gas station (five in one direction, five in the opposite direction), every time starting with full EV discharge.

    The second ten runs might also need full EV discharge, because HV mode may still use EV range at times.

    This testing would be very time consuming and costly, unless it can somehow fit into someone's normal driving routine. Even then, it would take a lot of detailed record keeping, and extra stops at gas stations. There are still errors, such as how accurate "full" tank is, after the click at the gas station. Gas gauge bars before and after could also be recorded for comparison.

    Graph the resulting data, showing error bars. In other words, stop fudging "calculations" to try to prove a desired outcome, but make some actual relatively unbiased measurements and present the data for whatever it shows.

    One-off trip data under different conditions is relatively meaningless and useless for this type of study.
    Last edited: Apr 15, 2018
  18. Viking79

    Viking79 Well-Known Member

    Using HV Charge should never be as efficient as HV mode since it has battery charge/discharge efficiency to worry about. Even if motor runs more efficiently in that mode, you will lose it due to conversion to chemical storage.

    However, in short test I ran in Volt, started dead battery, drove CS mode, 40 miles, 40 mpg. Did similar route starting with dead battery and used mountain mode to charge for a while and drove off added miles, similar 40 mile total and saw 42 mpg (slightly better, but not identical conditions). Both as calculated by computer. This was enough to tell me that they were similar, but I would still expect CS in Volt or HV in Clarity to do better or equal to HV Charge.

    For Clarity, I never use HV Charge, but do switch to HV at half to hold larger buffer and reserve EV miles for city driving at destination since the transmission in the Clarity does better with gas engine at higher speeds when it can run directly from it instead of in CVT mode. CVT mode is fine for efficiency at lower speeds. In this mode you aren't storing as much energy in the battery, instead the generated electricity is going to power the traction motor directly, avoid conversion losses there, but gearing is not ideal for high speeds.
  19. megreyhair

    megreyhair Active Member

    If your calcuations is correct, then it would be a lot cheaper for me to use HV charge than plugging in. Gas by me is $2.50 a gallon. Using your math, I would be paying 9 cents a kw, which is 3.5 cents cheaper per kwh or 25% cheaper......
    Maybe I shouldn't charge at home anymore . Charging at public level 2 chargers are like 4 cents a minute, which is even more expensive. 8(
  20. KentuckyKen

    KentuckyKen Well-Known Member

    Thank you Viking79 for reminding all that the Laws of Thermodynamics are not to be trifled with.
    Johnhaydev likes this.

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