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

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    We have no gas line, but propane price usually follows very closely to gasoline and other petroleum products prices. I am sure it is higher now. Our oil burner is over 20 years old. I am seriously thinking of replacing it with a high-efficiency propane burner. But it is not going to be cheap. Here goes the money for Mach-E.:cry::cry::cry:
     
  2. vvillovv

    vvillovv Senior Member

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    sorry to hear bout the mach-e sadness, whether you were serious or joking :rolleyes:
    I wasn't expecting a pessimistic party after spades comment, but here we are. I shouldda kept my thoughts to myself. Just switch optimistic with pessimistic in my post back there and see if it takes on a new meaning.

    I know that many here think the basic rules of physics can be applied to all things Prime related and typically they can if the laws are understood well enough.
    Personally I respect the rights of PC posters to explore as many "side cases of Prime behaviors" that have been noticed while driving. Mostly, because I know how different the Prime behaves just by changing one or two variables during a similar driving session. Add knowing how much history data plays into Prime behavior helps anyone understand some of why the car does what it does, typically.
    I see a lot of good ideas in both sides of the SalaKing Gorken discussion to try to make a suitable controlled set of variables to satisfy na bisc thought for making what 2 have noticed as (what I'd describe it as) a side case of Prime behavior, into a test proven normal case. It's probably possible to make a control case on a perfect track, out in the wild, maybe not so easy.
    I don't really have any ideas about how to narrow down the possiblities of testing for CHG mode efficiency ATM. Mostly because I'm doing my own thing in a different side case (let me call it) Staying in the EV range of HV mode). Keep in mind it's a side case, Don't do this at HOME.
     
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  3. Salamander_King

    Salamander_King Senior Member

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    Agreed. Even with no changes in the driving style or mode, my day-to-day commuting shows wide fluctuations in both EV efficiency (miles/kWh or EV range) and HV efficiency (mpg without EV mode driven distance). Trying to keep constant SoC at 10% is just way too hard and still subject to a milieu of uncontrolled variables.

    In any case, whatever the driving results I observe under my normal driving conditions are not likely to be universally applicable to all the PP drivers and vise versa. The only reason I am interested in testing CHG mode use efficiency was that with my rudimentary understanding of the law of physics that states conversion of one form of energy into another form always results in some loss (heat). Thus, I was firmly believing that using CHG mode to convert gasoline energy into electric energy for the traction battery will result in a loss of efficiency. This I thought was meant that driving on pure HV mode is always more efficient than using CHG mode and then EV mode from the charge. But, maybe under some conditions, it is not always the case. That is all I wanted to test.

    BTW, as a side note about "conversion of energy", I am having an HVAC contractor stop by today to give me an estimate on our aging oil-fueled boiler system to a much more energy-efficient propane system conversion. I will see if the conversion makes sense financially and energetically ... or it may still be better to use the money to buy a Mach-E to forgo the gasoline engine in my commuter car. LOL;)
     
    #43 Salamander_King, Oct 13, 2021
    Last edited: Oct 13, 2021
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  4. vvillovv

    vvillovv Senior Member

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    :barefoot:
    indeed ! mine too. Even within only 2/10th of a mile from start in EV mode. From between 10 miles/kWh to 89 miles/kWh. Yes it's a slight decline with no use of the Go Pedal. After that it's a slight uphill where the Go Pedal is needed to keep the car moving, and I'm sure anyone can guess what happens then.
     
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  5. KYBlue

    KYBlue Active Member

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    Not an engineer (one that matters in this regard anyway). But my "theory" is that, if I'm on the highway driving at 75 and the engine is running, and chg mode is on, the car is going to be engine powered regardless, and I'm only adding slightly additional load to generate charge for the battery, if I start going down hill/coasting then much more power is diverted for this cause. I think that, in some cases, it probably makes sense just looking at the basic math of MPG over the course of the drive, if CHG mode is only "costing" me 10-15mpg, but I can then shut the engine off and cruise for 20 miles at 999mpg - well..... But I did this only playing around, i'd say day to do with no liquid cooling of the battery that on say, a 1000 mile vacation drive I wouldn't want the battery hot from charge/discharge non-stop the whole trip...

    Hopefully someone smarter than me could figure it/graph it all out.... otherwise when I'm bored on my hour drive, I'll continue to experiment.


     
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  6. vvillovv

    vvillovv Senior Member

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    From Scary Movie "But Wait - There More" Those 2/10ths of a mile have slight bumps and is domed in the middle. The bumps become more noticeable on the daily Miles/kWh gauge with 25.5 inch tire diameter as opposed to the OEM 25 inch diameter tires. Finding the best groove in the road around other cars parked on the street alternating days and the lowest parts of the bumps or domes I have to go over is always fun, as long as no one else is around watching me go "2 mile an hour so everyone can sees me" Luda feat: playaz circle
     
    #46 vvillovv, Oct 13, 2021
    Last edited: Oct 13, 2021
  7. vvillovv

    vvillovv Senior Member

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    I think the laws of physics will agree with you. I ain't no scientist neither, but - it's a long sad for me story I may tell some other time out of the therapists office :whistle:.
    I've done CHG mode on a 50 mile trip at 70 with 0 EV available at the start, but my results from that one time were not as good as other times I've used CHG mode at different speeds and topographies.
    But I do see the logic, the possibility and have little doubt about what was noticed. I also fully understand the frustration of trying to explain what was observed. In case you haven't noticed yet, there are more doubters here at PC than there are open minded individuals.
    Can you imagine, what percentage of the human brain would need to be available to fully understand all the intricacies of Space Time as it bends twists and folds?
     
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  8. Salamander_King

    Salamander_King Senior Member

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    So, here is a formula-based calculation for driving the same route, same distance, under a perfectly controlled environment everything being equal, the only difference being the use of CHG mode and subsequent EV mode from the charge gained.

    I made the following table on Excell. The only numbers I need to enter are in Green. Everything else is automatically calculated from the numbers entered. Two factors affect the CHG mode efficiency.

    The first is the mpg factor which is how much mpg loss you will see when CHG mode is enabled compared to an identical drive situation with HV mode. From many observations by people experimenting with CHG mode, this number is about a 30 to 45% loss. That is if you were getting 60mpg on HV mode, then you will see 42mpg (best) to 33mpg (worst) when you use CHG mode. This of course will vary depending on the load, terrain, speed, etc. But for the sake of argument, we will assume everything stays the same before and after hitting CHG mode.

    The second is the EV gain factor which is how many miles of EV range you gain by driving 1 mile of CHG mode. This of course will also vary depending on the speed of travel under CHG mode and EV mode and other variables. But again for the sake of argument, we will assume this is some constant number one can attain by driving CHG mode for a certain distance and using that charge on EV mode later. For my single experiment above this was ~1, that is 1 mile of CHG mode resulted in 1 mile of EV range, but for @KYBlue at a much faster speed, it was ~0.5, that is every 2 miles of CHG mode resulted in 1 mile of EV range. So this factor is somewhat still unknown or maybe a much wider possible range for now.

    Once we have sufficient numbers of data and we can agree on numbers to use for those two factors, then the rest of the calculations are very simple. Assume your average HV mpg is EPA standard 54mpg and plan to travel 60 miles. CHG mode mpg is determined by the mpg factor above, and EV range possible is determined by EV gain factor above. So, for this 60-mile travel, driving 25 miles with CHG mode and driving 25 miles EV mode, and filling the rest with HV mode will give you the result below.

    upload_2021-10-13_13-13-55.png

    If the EV gain factor is more closer to @KYBlue which was 0.5. Still, I get the following result.

    upload_2021-10-13_13-15-19.png

    In fact for this travel, if I accept mpg factor of 30% loss and average HV mpg of EPA rated 54mpg, and 60 miles trip using 25miles CHG mode, CHG/EV is always better overall mpg until the EV gain factor is below 0.42, meaning for every ~2.4 miles of CHG mode you gain only 1 mile of EV range.

    upload_2021-10-13_13-16-34.png

    So, from those numbers, it seems unless EV miles gained by CHG mode is so poor, CHG/EV mode gives better overall mpg than HV mode.

    I don't know how to upload an active formula containing a spreadsheet file, so the table above are all screengrabs. The real .xlsx file has all the underlying formulas to enter and change the values on the fly.
     
    #48 Salamander_King, Oct 13, 2021
    Last edited: Oct 13, 2021
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  9. dtsexpert

    dtsexpert Member

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    $4.20 is cheapest cash transaction here in San Francisco.
    We re at 89% EV, our EV rate is 19c from 12am - 3pm. We re just glad to get the PP right on time back in May
     
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  10. dig4dirt

    dig4dirt MoonGlow

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    I know a Prius/Prime deals with generators and batteries and inverters,
    but I was just thinking when sitting in a fast food drive thru just tonight.

    An early 90s subaru was sitting behind me idling. Every 2 minutes the rad fans kicked in
    and since the car was very loud (had my windows down) I could hear the engine increase rpm significantly.
    Now I know being older it probably had sh!t for mpg, but I kept thinking.
    The engine is calling for the 12v to be charged faster I suppose, as the fans were electric.
    But the engine also increases to circulate the coolant faster too?
    Who knows....maybe not relevant. But made me think (sorry if I am losing you here, keep reading)

    MG1 and MG2. What if both are spinning, but if the call or need for only one to provide power (lower demand)
    Can the other provide/generate charge? So in HV mode using the engine, both MGs can charge?
    (sorry I read the forums here a lot and watch weber a lot, but dont pay attention much when my mind wanders :) )

    If that is the case, then on higher demand (higher speeds or uphills etc) then this would show less EV miles
    created by CHG thus having to use both MG1 and MG2 to propel.

    I thought weber or here, that in the Prime (or Gen4 also?) that both MG1/MG2 can provide power but older Gen's
    did not. I could be wrong on that.
    But still trying to figure this out in words.

    Even if all Prius MG1 AND MG2 can provide charge while providing propulsion, the Prime has to be programmed
    much differently then the non Prime Prius (aside from eco) same EPA MPG but heavier with the larger batt etc.
    Maybe aerodynamics play a role in that too.

    Im sorta blabbing but hopefully can spark someones brain cells lol.

    Gonna watch the weber vid, Ahhhgain. haha
     
  11. Gokhan

    Gokhan Senior Member

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    With the Prius Prime having 3–5x the mpg of a regular car, who cares about the gas prices. ;)
     
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  12. Gokhan

    Gokhan Senior Member

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    I posted several excerpts from the new-car features manual in this thread if you read from the following post on. There is also a nice animation video linked.

    Regenerative Braking Details? | Page 3 | PriusChat
     
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  13. dig4dirt

    dig4dirt MoonGlow

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    Found that "heretical mode"
    (sorry didnt finish the thread u linked, but I will have to start at beginning sometime, good stuff!)

    Possible that both MGs are contributing to the CHG at some points.
    Therefore in low acceleration points of driving, we could have a net gain of energy.

    There is a fella here on PC that could have would have done this testing as he has done many in the past,
    however he moved on to the "T" world vehicle and no longer owns a Prime...

    I will have to try a few test trips to give Salamander King some inputs.
    Not sure when that we be....hopefully soon.
     
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  14. Salamander_King

    Salamander_King Senior Member

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    Yeah, for the purpose of comparison in silico, all I need is more data points for the two factors shown below. Anything else is extra that is not needed for the direct comparison.
    • The first is the mpg factor which is how much mpg loss you will see when CHG mode is enabled compared to an identical drive situation with HV mode.
    • The second is the EV gain factor which is how many miles of EV range you gain by driving 1 mile of CHG mode.
    If anyone wants to experiment more in detail, then keeping EV ratio, Average MPH, driven miles on each section, SoC lever before and after, and type of driving conditions such as terrain, weather, temperature, loads in the car, wind, etc are good record-keeping but nor really necessary.

    I realized that I can test and get more data points for those two factors on my routine 36 miles round trip commuting easily. All I have to do is drive the entire 36 miles on HV mode and record the mpg for each direction separately, then compare that to driving CHG mode one way on a separate day and record the mpg on the CHG mode direction and EV miles gained for that section. For completeness of comparison, I should do the CHG mode in both directions on separate days. If I do enough trials, then I should be able to get average numbers for those two factors I can use for my routine commuting route calculation.

    Of course, the problem right now is that gas cost way too much to operate my PP. I would not have hesitated to do the testing when the gas was $2 and I had no free charge at work. But now, with the cost of gas at $3.25/gal. Using the single data point number for my commuting, it costs $1.95/day on HV, $1.77/day on CHG/EV. With the EV charge from the wall at home, it is now costing me only $1.32/day. And if I use a free charger at work, then it is $0.00/day

    upload_2021-10-14_11-40-22.png
     
    #54 Salamander_King, Oct 14, 2021
    Last edited: Oct 14, 2021
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  15. phlack

    phlack Junior Member

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    I'm wondering if someone can more completely explain why running in HV mode at a low SoC is less efficient than running it at, say, 50%?

    Thanks!
     
  16. Salamander_King

    Salamander_King Senior Member

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    The idea is that with SoC above 10%, PP has more traction battery buffer for the HV mode to operate without firing the engine frequently. At low or no SoC, the PP is basically the same as the regular Gen4 Hybrid Prius but heavier. However, with my driving conditions of regular commuting ~36miles rural roads no heavy traffic going 30mph average, I did not find a noticeable difference in mpg with and without SOC. So if the SoC level affects the HV efficiency, it is not universally applicable to all driving conditions.
     
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  17. mountaineer

    mountaineer Junior Member

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    Not to get off topic, but have you looked at a heat pump? Seems to be the way to go for a PP driver!
     
  18. Salamander_King

    Salamander_King Senior Member

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    Yeah, had multiple contractors stop by and come up with a proposal. Two major issues with the heat pump. Cost and effectiveness. It cost more compared to oil or propane boiler replacement even with some federal and state incentives. And It is not likely will save any money on the cost of fuel either with our very high electricity rate. We currently have hot water baseboard-type radiators. There is no ductwork in our house. Meaning any forced air type conversion will require either having a central heat pump unit with retrofit ductwork which is almost impossible in our house with a completely finished basement and very little room in the attic, or mini-split units in each room meaning again not plausible for the cost of the unit and number of unit required. And, even the most advanced and most efficient air source heat pump is not likely to be effective in heating in the middle of winter when the temperature gets to low single digits to below zero F (-20C or below) requiring supplemental heat source for those days, meaning I have to keep the existing boiler and heating system in place.

    If I am building a new house, then I may consider installing a geothermal heat pump, but in reality, if I am to build a new house, it will most likely be an off-grid tiny house with mostly passive solar heating.
     
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  19. PiPLosAngeles

    PiPLosAngeles Senior Member

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    The most accurate test having the least number of variables would simply be to precisely determine how much gas is required to generate 1 kWh of electricity in charge mode. Knowing how far we can drive with 1 kWh vs how far we can drive with the amount of gas required to generate that kWh determines the conclusion.

    I know my Honda EU2000i generator can generate 8 kWh using a gallon of gas. It follows, then, that a full charge of the Prime would require ~6.5/8 = 0.81 gallons. Since I already know I can routinely drive ~40 miles on a charge, that means I can achieve 49 mpg using a generator to charge my Prime. Not as efficient as HV mode. We just need to figure out the numbers for charge mode.
     
  20. bisco

    bisco cookie crumbler

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    would there be variability based on speed, load, etc?
     
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