1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Can using CHG Mode be more efficient?

Discussion in 'Prime Technical Discussion' started by Salamander_King, Oct 8, 2021.

  1. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    For this experiment, the SoC level should be started at 0%. I am not comparing wall-charged EV mode. The question is, does converting gasoline energy to electric energy and using it on EV mode make it more efficient than just driving the car on the HV mode. Charging the battery from the wall complicates the comparison.
     
  2. Gokhan

    Gokhan Senior Member

    Joined:
    Oct 5, 2008
    4,194
    1,690
    0
    Location:
    Paramount CA
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    As I said, Prius Prime loses HV efficiency when the SOC is at 0%. It's cheating when using the charge mode for this reason. Start it at, say, 20% SOC and end it at it at 20% SOC to have a meaningful comparison.
     
  3. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    No. To keep the comparison simple, I will only drive on either in CHG mode or in EV mode (from CHG mode SoC only). There will be no switching back and forth. This way, the HV mode will be always driven with 0% SoC in either case. Besides, I have done driving my 2017 PP with 0% SoC or 100% SoC, but all drives on HV mode. Under my driving condition, I did not see noticeable differences in mpg. Maybe in very congested stop-and-go traffic under hypermiling conditions, you are seeing HV efficiency differences with or without SoC, but under my normal driving condition of ~35mph no stop-and-go traffic for ~40miles trips, there seems to be SoC has no effect on mpg.
     
    #23 Salamander_King, Oct 11, 2021
    Last edited: Oct 11, 2021
  4. Gokhan

    Gokhan Senior Member

    Joined:
    Oct 5, 2008
    4,194
    1,690
    0
    Location:
    Paramount CA
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    This is an apples vs. oranges comparison, and the results have no meaning. You lose about 5 mpg when you deplete the battery in the HV mode. By using the charge mode, you are regaining part of this 5 mpg by driving less with a depleted battery. So, any gains you are seeing have nothing to do with the efficiency of the charge mode.
     
  5. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I completely disagree. As I said, I have never seen any mpg gain on HV mode drive with SoC compared to without SoC under my driving conditions. So, that 5 mpg gain you are suggesting is absolutely irrelevant under my usual driving conditions. And, even if there is some benefit of mpg gain with SoC, that is just fine. As long as SoC gained is from CHG mode, then it is using the gasoline engine to gain that SoC which is now contributing to the overall mpg gain. So that is an overall increase in efficiency with the use of CHG mode compared to without using CHG mode. It is not a comparison of HV mode vs CHG mode. As we all know CHG mode mpg is always lower than similarly driven HV mode. I am trying to compare the overall efficiency with CHG mode and subsequent EV mode from the SoC gained vs. simply driving with HV mode. As long as the use of CHG mode for the same driving condition gets better mpg than without the use of CHG mode, then my original question is answered unequivocally as "Yes, under certain driving conditions using CHG mode can be more efficient than without using CHG mode."
     
    #25 Salamander_King, Oct 12, 2021
    Last edited: Oct 12, 2021
  6. Gokhan

    Gokhan Senior Member

    Joined:
    Oct 5, 2008
    4,194
    1,690
    0
    Location:
    Paramount CA
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    Charging the battery by going to the CHG mode is no different than the battery charging itself during HV driving, except that you're forcing it. So, you are actually effectively increasing the SOC allocation for HV driving, which is my point that your HV mileage will likely be a little higher if you don't let your battery depleted so that there is more wiggle room for HV optimization.

    If your goal is best fuel economy in HV driving, using the CHG mode is not the way to go. During HV driving, the SOC will gradually fall, and if you don't let it fall below 10%, you will already have the best battery optimization because the computer keeps stealing the SOC to do this optimization for you. Once your SOC is depleted, it can no longer fall and you are stuck with whatever optimization is possible with the little reserve left, and turning on the CHG mode won't be as efficient. Remember that my DTE is almost 800 miles, and that's partly because I don't let the battery depleted. Also, not letting the engine idle when you take off greatly helps. So, don't switch on the HV mode until you pass the first traffic light, with me typically about one percent SOC use until I pass that. Then, the engine starts at 21 mph, not wasting any fuel idling.
     
  7. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    It is not my goal to achieve the best possible fuel economy in HV driving. That is where you are making the wrong assumption. It is not about hypermiling PP by constantly driving under 30mph with very slow acceleration and deceleration and maximizing the regen in between to achieve the highest mpg possible. You have done that with your PP, and many others have done it with previous generations of Prius to achieve seemingly impossible high mpg. I have seen the record of Gen2 drivers getting over 100mpg, so I know it is possible.

    But that's not the point I am trying to test. I am certainly not trying to beat your mpg record by using CHG mode on my trips. Being possible is not always practical for day-to-day driving situations. What I am interested to test is under my normal driving conditions without any particular hypermiling techniques deployed, can using CHG mode be more efficient than not using CHG mode for the overall efficiency. I initially thought the answer was flat out "NO", but I am having some reservation to that notion now that I have seen some evidence that CHG mode use can sometimes be beneficial to the overall fuel economy. And for testing that, the SoC level is irrelevant. Of course, I can test it with some SoC left in the battery, but the use of the wall charge on any portion of driving is going to complicate the comparison. Plus trying to finish the travel with exactly at the SoC I started is going to be way too difficult than just using up all the SoC produced by CHG mode. If your intuition tells us that driving PP without SoC making it a pure Gen4 Prius hybrid car is going to be less efficient than having a larger traction battery to stock up the energy by using CHG mode and later on EV mode, then that is exactly what I want to test.
     
    #27 Salamander_King, Oct 12, 2021
    Last edited: Oct 12, 2021
    MTN likes this.
  8. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    how do you keep the battery at 10% of wall charge?
     
  9. Gokhan

    Gokhan Senior Member

    Joined:
    Oct 5, 2008
    4,194
    1,690
    0
    Location:
    Paramount CA
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    I need to drive a little faster than 30 mph on the freeways, where most my driving is. LOL

    He wants to drive with "--" SOC in the HV mode but use the CHG mode and then the EV mode to drop it back to "--." I suggested that he should start with higher than "--," which happens to be an undisplayed value a few percent below or a few percent above zero percent but not at zero percent, and not drop it back under 10% to maximize the mpg.

    However, "--" does not mean 0% SOC. It could be anywhere between −5% and +5%. How are you going to account for that?
     
    #29 Gokhan, Oct 12, 2021
    Last edited by a moderator: Oct 13, 2021
  10. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Again, it doesn't matter what SoC it is on. I am not comparing EV range or EV efficiency. The only thing I am looking at is the overall mpg for the same trip under similar driving conditions (since I can't control every variable, so it will not be identical).
     
  11. Gokhan

    Gokhan Senior Member

    Joined:
    Oct 5, 2008
    4,194
    1,690
    0
    Location:
    Paramount CA
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    It matters a lot. If "--" means +5% when you start and −5% when you finish, that's an equivalent of 3.3 miles in EV driving. Since your trip is 65 miles, your mpg will be overestimated by 5%, which is as large as the effects you are trying to measure.
     
  12. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Just like any variations of numbers in trials, it has to be averaged out. One experiment is not enough to show the conclusive result one way or another. If the beginning and ending SoC affect the result, then so be it, that's the natural variable just like everything else, like temperature, weather, wind, etc. Again, SoC can be set at 10% to start and finish, but that will make the driving so difficult and not likely the example of my ordinally day-to-day driving condition. The easiest way to do the testing is just to drive without having any wall charge. That way there is no contribution of electricity fed to the traction battery other than the engine under the CHG mode.
     
  13. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Well, I went to town today and saw the gas price jumped to $3.25/gal. I am postponing CHG vs HV efficiency testing. At least for a while, unless I have to do some unplanned longer drive when there is no time to charge my car. Most of my current regular drivings are within the EV range of ~37 miles. Especially I now have free L2 charge stations at work, my commuting can be driven 100% EV without paying anything. There is no point in buying gas to generate electricity using CHG mode to do the testing. For the first time owing PP over 4 years, the EV mode is the most cost-effective way of transportation.
     
    #33 Salamander_King, Oct 12, 2021
    Last edited: Oct 12, 2021
    dig4dirt likes this.
  14. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    yeah, $3.60 here, i love it.
     
    dtsexpert and Salamander_King like this.
  15. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    However, this is going to hurt me going into winter. I have to run on HV mode at least in the morning for heat. Oh, and I also have to buy oil to heat our house... :(
     
    dig4dirt and bisco like this.
  16. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    heat???? come on! :p

    yeah, oil is gonna be a bummer. we're on a cap, i forget how much. 3 bucks maybe?
     
    Salamander_King likes this.
  17. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    10,958
    8,836
    0
    Location:
    New England
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Today was unseasonably warm, but we already had a light frost last week. It is a matter of time, I have to turn up the thermostat above 60F. I just had #2 oil delivered to fill the tank for the first half of the heating season. I paid $2.95/gal. That's more than double what I paid last year. The highest price in 7 years. The last time I paid above $3/gal for heating oil was the first half of 2014.:eek:
     
  18. vvillovv

    vvillovv Senior Member

    Joined:
    Mar 19, 2013
    3,493
    1,231
    1
    Location:
    NY
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    I can get real gas about 15 miles away, both regular and high octane at 3.70 for the regular. Or 50 miles away, but only Premium at 3.35.
    Morning commute is nasty on EV range estimate, up 50' to the main st, than up another 200' in 3 miles in heavy impatient traffic. I've decided it's cheaper to use the ICE going in in the morning, even with current gas prices. I guess I'm just a cheap hypermiler at heart
     
    Salamander_King likes this.
  19. Gokhan

    Gokhan Senior Member

    Joined:
    Oct 5, 2008
    4,194
    1,690
    0
    Location:
    Paramount CA
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
  20. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    i read that natural gas has doubled. not sure if that is everywhere though. i suppose electron prices wull follow