MPG in Hybrid Mode

Discussion in 'Prime Technical Discussion' started by CEJ, May 13, 2019.

  1. Blauer Glimmer

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    Sounds more like EV Auto numbers to me. How many miles and under what conditions are you driving?
     
  2. Prius from Dad

    Prius from Dad Senior Member

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    Yes, I have. From Jan. 2017 thru July 2017, I was using HV only on my commute home (36 miles one way and no big elevation changes). During the colder months my mpg's were upper 50's to lower 70's mpg and during the warmer months they were low to mid 70's to low 80's.
     
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  3. CEJ

    CEJ Junior Member

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    This is an accumulation of in-town trips (30-40mph) ranging from a few miles upon to about 10 miles, now totaling about 50miles. I zeroed trip A and let the miles pile up. I have to remember to push the EV/HV button every time I start out (as you taught me, SK). If I forget to do this for one of the mini-trips, of course, the mpg would go up. But then it should come down when I put it in HV before the next trip. Not seeing this. So I think I am remembering pretty well. Seems to be holding pretty well on each trip in the mid-70's to 80. Could it be I am just a Olympic quality hypermiler and didn't know it? Glad to know what you have achieved; gives me a benchmark.
     
  4. CEJ

    CEJ Junior Member

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    Thanks, Dad. So I am not totally weird getting this. Great!
     
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  5. Salamander_King

    Salamander_King Senior Member

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    For a short trips like that I am sure you can get up to 70s mpg easily, especially if there are no sudden acceleration or large hills to climb. That said, in a short distance and small numbers of trips, one mini-trip on EV might be enough to bring the average up. When you mix EV drive in your current Trip meter, the car will not throw out that data next time when you push HV button.

    Suppose you did 5 trips of 10 miles each total of 50 miles. Say, you did all five of them strictly with HV and got 60 mpg on the Trip meter. That means you used 50miles/60mpg=0.8333 gal of gas. Or divide that by 5 trips, on average 0.1666 gal per trip of 10 miles. Now, if you forgot to turn the HV button in one of the trip, and luckily you had enough battery to drive 10 miles in EV not using gas at all. This would make 4 trips with 0.1666 gal per trip of 10 miles, or 4 x 0.1666 = 0.6666 gal of gas for the same 50 miles on the Trip meter (remember 10 miles is on EV). Now your mileage displayed is 50 miles / 0.6666 gal = 75mpg.
     
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  6. CEJ

    CEJ Junior Member

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    I totally dig your math, SK. But consider: suppose I forget to turn on HV during the 3rd segment of 10miles. Then after the first two segments, it will show 20/(2x.1666)=60mpg and after 3 segments, 30/(2x.1666)=90mpg, after 4 segments, 30/(3x.1666)=80mpg and after 5, 75mpg (as you say). Although this is not an exact model for my driving, if I forgot to turn on HV for some trip segment, I would expect to see considerable variation in the average mpg, particularly before and after that EV segment (if they are more than just a mile or two) and if I kept driving more miles (and remembering) it should stop varying so much. I don't think I am seeing that but more or less of a steady value around 75mpg which doesn't seem to be dropping or rising much. I will keep observing. Apparently Dad above got something like this, so maybe it is real. We shall see. Thanks for your interest.
     
  7. Salamander_King

    Salamander_King Senior Member

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    Yeah, the number is well within the car's capability. There was a lady who bought PRIME at a dealer on the east coast and drove it back to her home. She was claiming getting something like 80 mpg on her way home all on HV highway speed over thousand miles or something like that. I don't have a feather touch on my foot and no patience to hypermile like that.;)
     
  8. CEJ

    CEJ Junior Member

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    That is the amazing thing: that this car is capable of that kind of mpg, at least under some circumstances. Glad to have learned that from you guys. I have now attached a small square of masking tape to the steering wheel to remind myself (during this experiment) to be sure and push the HV button whenever I start out.
     
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  9. CEJ

    CEJ Junior Member

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    When traveling in HV mode, does AC (heat pump) derive its energy from the EV portion of the battery until that is used up and then go into the hybrid portion of the battery which is regenerated by the ICE?
     
  10. Salamander_King

    Salamander_King Senior Member

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    My understanding is that there is no "EV portion" of the traction battery. The car uses one and only traction battery whether you are driving EV mode or HV mode. So, if you have a full charge in the traction battery and upon starting a car and put the car into HV mode, it operates just like you are driving the car in HV mode after you have used up all EV range and the car forces you to drive under HV. What I observe is that if you have a full charge and switch to HV mode, and use AC or anything that requires battery power including some from 12 V battery, traction battery will provide that power. This uses battery charge, but ICE and regen brake will generate electricity and fill what is used to maintain the battery level, just like when you reach the HV mode after running out of EV range. You never "use up" the traction battery under HV mode.

    When I go to a big city I preserve traction battery charge for the drive within the city. If I start with 30 miles of EV range with a full battery at the beginning of the trip and start the travel on HV mode. While I am driving under HV for a few hundred miles on the highway with AC on, the traction battery level does fluctuate a bit, but I can keep most if not all of the full capacity until I reach the city for later use. I am very conservative on the use of AC so I can see if you use a lot of AC and other power hungry items in the car while you are driving HV with full traction battery, the car may not be able to generate enough electricity to keep up with the demand and dips into more on traction battery quicker, but I have not faced that situation myself.

    You might want to check this thread: saving EV till later | PriusChat
    Others are reporting similar but slightly different experiences. There is a report that traction battery charge will decrease without using any in EV mode over time. I have not seen this happens to mine beyond a few miles shorter reported on GOM after a few hundred miles of highway drive on HV. I find the following remark very intriguing, but I have never tried driving HV with only 80% charge. My 100% charge at the start is usually at ~95% or higher but I do not have enough data to confirm my vague recollections.

     
    #30 Salamander_King, May 18, 2019
    Last edited: May 18, 2019
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  11. CEJ

    CEJ Junior Member

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    So if I understand you, SK, in principle if you start out with battery fully charged and drive in HV mode, the battery should stay approximately fully charged until you switch to EV. Is the other remark suggesting that in HV mode that battery will only maintain80%
     
  12. CEJ

    CEJ Junior Member

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    ...of the original total charge?
     
  13. Salamander_King

    Salamander_King Senior Member

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    With my limited experiences of trying to save full charge of battery for later EV use, I was always able to save 95-100% of battery charge. This is after driving a few hundred miles on HV. Others have reported that full charge will decrease under HV drive down to 80% over time and stay there. Or if your charge is less than 80%, then HV will maintain the current level indefinitely.
     
  14. CEJ

    CEJ Junior Member

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    Got it. Thanks for clarifying. In my ongoing experiment driving in HV-only, it seems like my total charge is dropping. But I am not sure where it started, so it might be dropping to the alleged 80% from something higher. Need to be more aware of starting point next time around. In driving around town (multiple trips) in nice weather with mileage piling up, I am still getting 76mpg or a bit higher without much fluctuation.
     
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  15. CEJ

    CEJ Junior Member

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    Have now logged 100mi of HV driving (made up of a collection of trips of no more than about 6 mi). All-over mpg is about 80. My 2017 non-prime Prius, as I recall, never did better than about the 50's under similar circumstances. Yet both are rated approximately the same for gas-only driving. Can the difference be explained?
     
  16. Salamander_King

    Salamander_King Senior Member

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    Your previous car was regular 2017 Prius? Hummm, Gen4 Prius is an almost identical car as PRIME except for smaller traction battery and luck of plug-in capability. Gen4 should get very similar gas mileage with just HV drive.
     
  17. bisco

    bisco cookie crumbler

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    tough to compete with 80mpg, is anyone else averaging that high?
     
  18. CEJ

    CEJ Junior Member

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    Yes, it was a 2017 Prius 4 touring, not a plug-in. I agree, one would expect similar mileage. I made 4 sub-trips today of 4-6mi and made sure I was in HV mode. Interestingly, in the last couple of these, the mpg actually ticked upwards to 80.

    Apparently, a couple of others earlier in the thread got there.
     
    #38 CEJ, May 18, 2019
    Last edited by a moderator: May 18, 2019
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  19. bisco

    bisco cookie crumbler

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    do you ever plug in?
     
  20. Salamander_King

    Salamander_King Senior Member

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    80 mpg in short distance is doable, but I can't keep that kind of mileage for a long distance if I have to drive normal hours on my usual roads. You might want to try a tank without any charging to get accurate mileage from ICE only drive.
     
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