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Eco vs. Normal: HV vs. EV

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

  1. mveras1972

    mveras1972 Member

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    I’m sure that eco mode is more than just changing the sensitivity of the accelerator pedal.


    iPad ?
     
  2. Gokhan

    Gokhan Senior Member

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    Is it true that if the EV section (not the reserved HV section) of the battery is depleted, the gas mileage drops due to less efficient HV operation?
     
  3. Salamander_King

    Salamander_King Senior Member

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    Under strictly HV mode operation, I don't think there is any difference if all other variables are equal. Of course, if you are using EV mode mixed with HV mode then your mpg increases.
     
  4. jerrymildred

    jerrymildred Senior Member

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    There is speculation that driving in HV with at least a couple miles of EV range left results in the car using EV for longer stretches before charging the battery back up which yields slightly better mpg. But it's only a theory so far. I've played with it and I can't see enough of a difference to know if it's real or not. So I mostly just drive it and try to use up all the EV range (with the best efficiency that's not too much bother) before I get home or wherever I can charge for free. Even just driving it without gaming the system gets such great economy that it still boggles my mind.
     
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  5. Gokhan

    Gokhan Senior Member

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    Last night when my EV range was fully depleted, I felt like this speculation was valid. It felt like I was no longer able to get the typical 75 mpg without some EV range left. If you will do HV driving, it may help with the mpg to have a couple of miles left in the EV range.
     
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  6. jerrymildred

    jerrymildred Senior Member

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    In my driving, it's hard to be sure. Over 90% of my miles around town are EV, is it's not often that I go past my EV range and run the ICE. And on long trips, it's pretty much impossible to do any kind of valid comparison since there's no repetition of conditions. Best test would probably be on a closed track. That would take wind, elevation, and traffic variables out of the picture.
     
  7. vvillovv

    vvillovv Senior Member

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    Your speculation and mine are the same in regard to this question. It's still only speculation until others confirm or refute out findings, so don't hold your breath.

    I have 6 800+ mile trips down south and back up north again. The first four times back and forth I managed to deplete most of the EV charge within a hundred or two hunderd miles by forgetting to switch into HV mode after a stop. results for all 4 trips were mid 50's mpg.
    On the two occasions I remembered to switch into HV mode after every stop both down south and back up north my results were 72+ mpg down and low to mid 60's mpg back up north again in Dec..
    Another thing I noticed in both trips with full EV charge the entire trip was the the available EV charge never fell below 90% and would recharge back to 100%. I'm not asking anyone else to believe me either, I was as mystified by that happening as anyone reading this post will probably be.
     
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  8. Salamander_King

    Salamander_King Senior Member

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    I am confused. Why are you mystified? You drove entire trip in HV mode starting with a full SOC, making sure after each stop to switch back to HV and did not drive any portion with EV. Is that correct? My experience with that style of driving is that I can always keep 95% or up, and sometimes as you said 100%, of SOC retained after entire trip on HV. If you don't use EV range you can preserve almost all of SOC indefinitely. One caveat is that if your HV drive is very short and you don't have enough chance to regen, initial start up of the engine warm up will "eat up" a small portion of SOC usually about 5% but can be as high as 10% if the initial run is demanding like on a uphill. In a short HV trip, you may not regain this initial loss ever, thus your SOC will decrease.

    I wrote this in different thread, but here is my take on perceived mpg gain on HV mode with full EV SOC. I've done quite a bit of ~300 miles (one way) round trips in the past few months. I always save full EV charge going down to use it in the city. Having no way to charge at the destination, I am always near 0% EV on my way back. For those drives, I have seen mpg on my way back being either lower or higher compared to the way down with full SOC. To make any comparison, you must do the same route going the same direction with full charge vs no charge in very similar driving condition. Even with doing this, there are still too many other variables that come into play affecting mpg such as temperature, weather, wind directions, and other traffics. My feeling is that any differences in mpg are just coincidence.
     
    #28 Salamander_King, Nov 5, 2019
    Last edited: Nov 5, 2019
  9. vvillovv

    vvillovv Senior Member

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    Now that you mention it, I remember reading your post and was as mystified than as I am now by the logic of the coincidental difference in mpg.
    Let me try to explain and hope that you are not offended by my reasoning.
    You say on the one hand that one needs to drive both directions with full EV SOC.
    On the other hand your experiments give you only Full EV SOC in one direction.
    Adding to the confusion on my part is the fact that sometimes you get better mpg on the return trip without or with lower EV SOC than on the trip with Full EV SOC.
    Than there is the issue of never having Full EV SOC on the return trip to compare with an initial trip.
    And finally you give the opinion that any mpg difference is coincidental, without having done what you previously mentioned needed to be done ( having Full EV SOC in both directions ) for accurate data of this scenario.

    I'd like to hear more from @Gokhan because there are so few that seem to notice a difference, and all the conflicting data seems hap hazard to me.
     
  10. Salamander_King

    Salamander_King Senior Member

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    To be clear, my comment was copied from this thread: HV Mode: Does a Fuller Battery Improve MPG? | PriusChat

    It was written in response to the OP in the thread commenting on better mpg in HV mode on a way to the destination with a full EV SOC than on the way back with no EV SOC. And it was not any type of "experiment", simply observations I made from some trips I drove HV mode with or without EV SOC.

    If I am going to do an "experiment" I will do it with my commuting route in the morning. I usually drive all the way to my work HV and come home all the way EV in winter. During winter one way (~18 miles) usually depletes EV SOC. After depleting SOC, I can drive in following day without charging over night. I have actually done this pattern of driving many times in the past, but my daily mpg record is not accurate representation of HV mpg on the day I did EV drive home. So, if I am to do this "experiment" I will have to take a note of mpg only on the way to work and not include the way home. Also, if I do this now, 18 miles will not deplete 100% EV SOC, so I will have start with 50% SOC. Shouldn't take too long to get a few data points.
     
    #30 Salamander_King, Nov 5, 2019
    Last edited: Nov 5, 2019
  11. Salamander_King

    Salamander_King Senior Member

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    OK. I found some data points on HV drive with SOC near full. This is not any part of experiment to test the hypothesis that fuller SOC improves HV mpg, but give some idea of what to expect when I do the comparison.

    It is found in this thread: MPG in Hybrid Mode | Page 6 | PriusChat upload_2019-11-5_15-32-4.png
     
  12. Gokhan

    Gokhan Senior Member

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    I have very limited testing so far, but what you discovered seems to be what I'm seeing as well: 70 mpg in HV/eco mode with at least a few miles left in the EV charge, 55 mpg in the HV/eco mode with the EV charge fully depleted.
     
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  13. vvillovv

    vvillovv Senior Member

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    The other thing I noticed was that once EV miles shown of the GOM (guessOmeter) or EV SOC (state of charge) is used up, it doesn't recharge much above the HV reserve on it's own.

    I posted about another 100 mile trip in HV (50 miles in each direction) in late spring or early summer, where I had a 30 mph headwind the first 50 miles and 30 mph tailwind in the opposite direction. I got low 60's with the headwind and was a little disappointed that I couldn't get any more. I was really surprised getting 91.5 with the tailwind.
    Traveling most of the two trips at 55 mph with some 35 mixed in.. The trips were not exactly out and back, but they were both close enough to the same for my needs.
     
    #33 vvillovv, Nov 6, 2019
    Last edited: Nov 6, 2019
  14. Gokhan

    Gokhan Senior Member

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    Another curious thing is the Consumer Reports numbers under their Ratings & Safety:

    Prius Prime:

    CR'S overall mileage: 69 mpg
    CR'S city mileage: 56 mpg
    CR'S highway mileage: 81 mpg

    Prius:

    CR'S overall mileage: 52 mpg
    CR'S city mileage: 43 mpg
    CR'S highway mileage: 59 mpg

    However, they then go and say in their Road Test, "We got 50 mpg overall [with Prius Prime] -- two less than the regular Prius. This difference can be attributed to the Prime's 300-pound weight increase over the Prius."

    So, go figure.
     
  15. Salamander_King

    Salamander_King Senior Member

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    Yes, once EV range reaches zero, it is very difficult to bring it back out of the hole unless you use the CHARGE mode, or you have extremely long downhill to regen. I have noticed that too.

    CR's mpg may be using EV range? My understanding is that for all practical purposes, without EV range left, PRIME is the same as a regular Gen4.
     
    #35 Salamander_King, Nov 6, 2019
    Last edited: Nov 6, 2019
  16. vvillovv

    vvillovv Senior Member

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    50 overall ain't to shabby when testing everything the Prime does. Charge mode can put a big dent in mpg especially when used at higher speeds, but even at lower speeds it'll drop mpg really fast compared to what drivers normally see the Prime getting.
    85 mph in EV can also pull electrons from the pack kinda fast.
    But, HV, even at 85 is still really efficient when compared to most other cars.
    So, I guess it all depends on what they actually did during the test, as it's possible to drive the Prime
    really inefficiently. And as @alamander_King said above, without EV range the Prime is the same as a Gen4 + a nit picky extra 300 lbs.
    possibly some other traction pack concentric programming so far unidentified or unnoticed by either gen4 owners or prime owners
     
    #36 vvillovv, Nov 6, 2019
    Last edited: Nov 6, 2019
  17. jerrymildred

    jerrymildred Senior Member

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    Let me just toss in my opinion that having a full battery isn't any better than having a 1/2 or 3/4 full battery. If fact, it could be a detriment if you get into mountains or large hills since a full battery won't be able to absorb as much charge on long downgrades. Best to leave a little headroom just in case.
     
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  18. Salamander_King

    Salamander_King Senior Member

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    I have not read anyone claiming 100% SOC gets better mpg in HV mode compared to 50% or 25% SOC. I think the comparison is with SOC left vs 0% SOC on HV mpg. I have driven my PRIME on pure HV mode so many times sometime with SOC left, other times with 0% SOC, but have not seen clear trend favoring SOC left to get better mpg on my own car. In fact, even with the same SOC level, day to day mpg on my routine commuting can vary vastly, sometimes 85mpg a few days later 65mpg.

    The table shown on my comment #31 is for pure HV mode drive of my daily commute. first row of the same day is the morning commute and second row is afternoon return commute. As you can see, with near full SOC, 3 morning commute are 70, 63, 64 mpg, and 3 return commute are 74, 84, 64 mpg. There is a general tendency that I get better mpg on my return due to warmer temperature in the afternoon. But for the same return trip, the numbers vary widely. Yes, that's only three data points, but my impression is that so many factors affect mpg of any given trip, it is almost impossible to single out major factor acting out to cause mpg up or down. This includes SOC % left.
     
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  19. vvillovv

    vvillovv Senior Member

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    I'm no absolutely positive the Prime is programmed this way, but I've noticed that it adjusts (and sometimes much later than the PiP used to from memory ) to the driver input and the averages it calculates over time. Perhaps hours, days or life cycle, depending or all inclusive.

    Mountain driving is not something I've done yet and the gradients locally are not anything like out west on the ranges in the NE. and I know there are more techniques to use when driving a prime in the mountains.

    But when I'm driving for 8 or 12 or 16 hours at a stretch, I'm not wanting to pay that close attention to how the Primes systems behave. I'll pick one or two things I want to watch and ignore the rest.

    Like the trip down south I got 72 mpg, I drove from western NY past DC before I refueled. Might have almost been able to make Richmond, VA if the wife stopped nagging me to get gas.
     
    #39 vvillovv, Nov 6, 2019
    Last edited: Nov 6, 2019
  20. Gokhan

    Gokhan Senior Member

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    Yep, the claim is that the Prime may be getting substantially higher HV mpg (perhaps 25% higher) with some EV charge (about 10% or more) remaining vs. no EV charge remaining at all (close to 0% EV charge). It makes no difference in the HV mpg if there is 10% vs. 100% charge.
     
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