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Comparison of two paths for an EV trip

Discussion in 'Prime Fuel Economy & EV Range' started by jb in NE, Jul 22, 2019.

  1. jb in NE

    jb in NE Senior Member

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    Attached to this post are two files generated by Hybrid Assistant that nicely show the increased efficiency you can gain with your Prime if you avoid the highway and use surface streets. This was a roundtrip to downtown. Starting with a full charge, outbound from home about 60% of the drive on Interstates with 65 mph speed limit. Return trip surface streets with no Interstate. Edit: 100% EV even though the software says otherwise.

    The graphs show the significant difference in regeneration opportunities and lower energy required to propel the car on surface streets. The trade-off is that the highway is quite a bit faster.

    Note that Hybrid Assistant reports battery as a percentage of potential full charge, not indicated full charge. 100% indicated on the dash is about 83% on Hybrid Assistant.

    Outbound trip (10.75 miles) consumed about 2.4 KWh net, return trip (10.43 miles) consumed about 1.7 KWh net.
     

    Attached Files:

    #1 jb in NE, Jul 22, 2019
    Last edited: Jul 22, 2019
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  2. Salamander_King

    Salamander_King Senior Member

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    That's the number (82-84%) I am getting on my PRIME for 100% EV SOC on dash. Do you know what the Hybrid Assistant shows on it's SOC when EV range is depleted? Mine is 13-15%.

    Do you have the data for hybrid battery energy that shows kWh out and kWh in for both legs of the trips? Your Energy graph shows those numbers, but I would like to see the printed number. It looks like this.

    Hybrid assistant report.png
     
    #2 Salamander_King, Jul 22, 2019
    Last edited: Jul 22, 2019
  3. jb in NE

    jb in NE Senior Member

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    I should have included them in the files I made, but missed it. Good catch; I have updated the posted files to include this on the second to last page.
     
  4. Salamander_King

    Salamander_King Senior Member

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    Thanks for the update. So, here is something that is bothering me. If I assume your two runs were 100% EV despite the fact the reports say 98% and 99%, ICE did not start, so the miles driven are from the battery. Since 100% of miles driven were EV, from SOC% change and amount of kWh of battery used (delta of out of battery and into the battery in kWh), I can calculate full capacity of the battery. Also, assuming that the EV portion of SOC is 15% to 85% in the battery, I can also calculate the EV portion of the energy used in kWh.

    This number should be about the same no matter how you drive the car. I have tried 5 times now with very similar driving conditions for my commuting. The number I get for the FULL SOC is very similar to your surface result. Similarly, my FULL EV SOC portion of kWh is very similar to your surface trip. BUT, your expressway result is way off from those averages.

    The average of my 5 trips + your surface trip: 100% SOC in kWh ~7.82kWh, 100% EV SOC portion in kWh 5.42kWh
    Your surface trip: 100% SOC in kWh ~7.74kWh, 100% EV SOC portion in kWh 5.34kWh
    Your expressway trip: 100% SOC in kWh ~8.41kWh, 100% EV SOC portion in kWh 5.81kWh

    Of curse, we all know the spec of the full capacity (100% SOC) of the battery is 8.79kWh. The average of mine and your surface run results is too small. Your expressway result is closer to the spec but still bit short. I don't know why the discrepancies unless Hybrid Assistant is reporting numbers I'm not really understanding what they mean.

    Screenshot 2019-07-22 at 7.12.40 PM.png
     
    #4 Salamander_King, Jul 22, 2019
    Last edited: Jul 22, 2019
  5. jb in NE

    jb in NE Senior Member

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    It was a 100% EV run both ways - I don't know why HA shows what it does. Some oddity of the software.

    I don't know that should be true. Battery discharge rate can significantly affect the total amount of energy delivered from the battery.
     
    #5 jb in NE, Jul 22, 2019
    Last edited: Jul 22, 2019
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  6. Salamander_King

    Salamander_King Senior Member

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    Discharge rate and amount out from the battery as well as regenerated energy, yes, they are dependant on how you drive. Your data clearly shows that. The "number" I was referring to is the full capacity of the hybrid battery in kWh deduced from the data. That should not change no matter how you drive.
     
  7. jb in NE

    jb in NE Senior Member

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    The reason I think it will change is that the battery discharge rate during the time the data was taken was higher in this case, which may skew the data from HA. Then, when you attempt to extrapolate from that data, you get a different conclusion than when you use other data from slower discharge events.
     
  8. Salamander_King

    Salamander_King Senior Member

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    That maybe. But, SOC % used up during the trip and the number of kWh used from the traction battery for that trip should give constant full battery capacity otherwise I don't know what those numbers really mean. An analogy would be if you know the data for % of gas tank depleted during a trip and you know how much gasoline was used during that trip, you should be able to calculate the full tank capacity from them. Wither you drive 100mph on highway or 30mph on surface roads, the number should come out close.
     
  9. jb in NE

    jb in NE Senior Member

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    I don't know the answer. I haven't used the Hybrid Assistant data to calculate the full EV capacity. I use the software to analyze my drives for opportunities for improvement (regeneration, coasting, etc). Essentially, to train my feet.