Eco vs. Normal: HV vs. EV

Discussion in 'Prime Fuel Economy & EV Range' started by mr88cet, May 26, 2019.

  1. Gokhan

    Gokhan Senior Member

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    I am pretty confident at this point that the Prius Prime PEHV has substantially higher fuel economy than the Prius HV.

    I had a 110-mile round trip in the HV mode with eco mode yesterday. It was mostly highway driving, with typical speeds in the 50 - 65 mph range, going through hilly areas at times, temperatures in the 60 - 80 °F range. Part of it was stop-and-go or city. I was monitoring the EV battery, and the usage of the EV battery is aggressive -- typically charging and discharging to 5 - 10% of the capacity. I verified that the initial and final EV battery level were the same. I averaged 75+ mpg. I doubt you could get this gas mileage with the Prius HV. I think the EV battery is substantially helping optimize the HV driving, as long as you have at least about 10% EV-battery level left.
     
    #41 Gokhan, Nov 14, 2019
    Last edited: Nov 14, 2019
  2. Salamander_King

    Salamander_King Senior Member

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    I will post the initial result of my experiment on my PRIME's HV MPG difference with EV SOC vs without EV SOC on a small set (n=3 each) of data, but I can tell you now it does not look like there is much difference at least under my driving conditions.

    I don't have any way to compare PRIME HV mpg to regular Gen4 mpg, but it is hard to believe it will be much different between those two cars under identical conditions.
     
  3. vvillovv

    vvillovv Senior Member

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    Here is a thread in the Gen 4 section and this Prius is doing pretty well so far too.
    Going to miss the summer... | PriusChat

    it might be a bit above normal, or maybe we should be watching more closely to see if any secrets get revealed.
     
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  4. Tideland Prius

    Tideland Prius Moderator of the North
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    At highway speeds, it’ll be tough to get over 70mpg on a Gen 4. We have the Touring with the 17” alloys and we’re at 55mpg at 70mph which is pretty impressive in its own right.

    City driving in the summer > 12-15 miles trips will see over 60 easily. Maybe 65mpg. (70 if you can take it slow).

    On my Prime, I’m sitting at 65mpg on the highway in HV mode (no charge).
     
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  5. Salamander_King

    Salamander_King Senior Member

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    So here is my initial experiment result on mpg comparison on PRIME, HV mode with SOC remaining for EV vs NO SOC remaining for EV.

    The condition was all for my morning commute of 17.7 miles on the same route at about the same time except one day I left bit later than usual. Big variations were the daily temperatures and road conditions. We had some snow and ice for two days for this period. I did one drive with SOC and one drive NO SOC.

    with SOC: Mean 58.867, sd 3.470, sem 2.004, n=3

    NO SOC: Mean 59.233, sd 3.630, sem 2.095, n=3


    P value and statistical significance:
    The two-tailed P value equals 0.9055
    By conventional criteria, this difference is considered to be not statistically significant.

    Here is the raw data used.
    HV mpg.png
     
    #45 Salamander_King, Nov 15, 2019
    Last edited: Nov 15, 2019
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  6. vvillovv

    vvillovv Senior Member

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    I'm not surprised by the results shown in the experiment above. All HV for 18 miles

    I will say the thing that jumps out at me in the raw data is the start and end SOC.

    edit out comment about HVAC settings to reduce confusion regarding efficiency.
     
  7. Salamander_King

    Salamander_King Senior Member

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    SOC reading was off from Hybrid Assistant. ~14% SOC is equal to 0% SOC on MID (i.e. no EV range remaining). Anything below 14% SOC is not displayed on MID. I wanted to check that there are no more SOC used when there are EV SOC remaining. At least the numbers reported by HA do not suggest the car is utilizing more traction battery available under strictly HV mode drives. In fact the SOC utilized is slightly higher when there is no SOC remaining although the difference is not statistically significant (P value equals 0.1085).

    The HVAC settings were set manually with the Fan at 2 bars, AUTO OFF, A/C OFF, Recirc OFF, in Eco mode and S flow Driver priority with direction of air to window at 70F on the day defogging was needed as shown in the photo below. On days I did not need defogging HVAC was OFF.
    IMG_20191115_062649.jpg

    Here is the data for ECO AC score bars at the end of each trip. "no" means there was no Eco AC score bar shown since I did not use HVAC for the entire segment of that trip. I also added delta SOC data.
    hv mpg3.png
     
    #47 Salamander_King, Nov 15, 2019
    Last edited: Nov 15, 2019
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  8. Gokhan

    Gokhan Senior Member

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    What I've found out is that the Prius Prime PHEV is actually using quite a bit of the EV battery in HV driving. On every HV trip, I seem to be losing a few percent of the EV charge. That partly explains the seemingly higher fuel economy of the Prime over the vanilla Prius. However, I think the Prime is still more efficient than the vanilla Prius because of the better use of a bigger battery. At the end it's hard to separate the increase of the fuel economy in Prime from the EV usage during HV driving (EV-battery depletion during the HV trip), but it makes sense that it gets a little better fuel economy than the vanilla Prius due to more flexible EV kick-in, despite being a little heavier.
     
  9. jerrymildred

    jerrymildred Senior Member

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    Not losing. Borrowing but not usually getting it paid back just as you shut it off. The remaining range will fluctuate by a couple miles, mostly under the point where you switched from EV to HV. It will use EV for a while and then put it back. If you shut it off just as it finishes paying back the loan, then you won't lose any EV range. Chances are, it will be a little under that starting point, though. But I always figured that if I got back from a drive long enough to use all or more of the range and had any range left, I was wasting gas money. For example, we drove 181 miles yesterday and got home with 1 mile of EV range left. could have done better, but the computer showed 68.0 mpg. ;)
     
  10. mveras1972

    mveras1972 Member

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    I’ve found that while in HV, my Prime will make sure to maintain the % charge. For instance, if the charge is 62%, it will start the engine if it drops to 61% until it is back at 62% and then turn off. It will use EV until it drops again or if I push the accelerator hard enough and then the engine starts again.

    By the way, what does SOC stand for?


    iPhone ?
     
  11. Salamander_King

    Salamander_King Senior Member

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    State Of Charge
     
  12. mveras1972

    mveras1972 Member

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    Thanks Salamander. I am not convinced that you get better MPG if the EV battery is charged up. Driving with or without any EV range, the engine seems to behave the same way. So I’m not really convinced there’s any improvement in MPG just from having EV range alone. I believe the improved MPG comes from using HV for highway driving and saving your EV range for city driving. That’s how I tend to use it. However, when it is very cold, the engine can start even if in EV mode, and when you turn on the front defrost so that reduces your overall MPG in the winter.


    iPhone ?
     
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  13. Salamander_King

    Salamander_King Senior Member

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    Yap, a small sample of trials I have done seems to agree with your observation.
     
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