Estimated EV penalties for various heating cooling and lights

Discussion in 'Prime Fuel Economy & EV Range' started by Skylis A, Nov 21, 2017.

  1. Skylis A

    Skylis A Senior Member

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    Traction battery: 351.3 V, with 6.1 kWh available capacity in EV Mode (SOC limits of 14% HV only to 83% fully recharged)

    Example of average current draw per town trip, assuming average trip speed of about 26 mph: 15 amps. This translates to EV range of about 30 miles.

    So, let's take 15.0 amps and 30.0 miles on EV as our reference figures.

    Here are the sources of current draw that I measured with my ScanGaugeII. Two successive 20-second trials with a 20-second break in between. Units are in the column labels. % dif. is relative to 30.0 miles as in the example that I described above. % dif. does not use prerounded values for EV Range.

    Source of draw Current drain (A) EV Penalty (mi) EV Range (mi) % dif.
    1 Heated steering wheel 0.2 0.4 29.6 1.3
    2 Two seat heaters low 0.1 0.2 29.8 0.7
    3 Two seat heaters high 0.3 0.6 29.4 2.0
    4 Daytime running lights Less than 0.1 too low to measure 0.1 29.9 0.3
    5 Mid beams Between 0.05 and 0.1 0.1 29.9 0.5
    6 Normal night beams 0.2 0.4 29.6 1.3
    7 Normal night beams with Advanced lights 0.25 0.5 29.5 1.6
    8 High night beams 0.35 0.7 29.3 2.3
    9 Heat face only open vent driver priority ECO heat fan speed 3/7 at 74 degrees 4.6 to warm up decreasing to 1.5 after two minutes in my test 2.7 27.3 9.1
    10 Heat face only open vent driver priority ECO heat fan speed 1/7 at HI 5.0 decreasing to 2.2 after two minutes in my test 3.8 26.2 12.8
    11 Heat face only open vent driver priority ECO heat fan speed 7/7 at HI 5.0 7.5 22.5 25.0
    12 A/C face only closed vent driver priority ECO cool fan speed 1/7 at 68 degrees 0.5 1.0 29.0 3.2
    13 A/C face only closed vent driver priority fan speed 3/7 at 68 degrees 0.7 1.3 28.7 4.5
    14 A/C face only closed vent driver priority fan speed 7/7 at 68 degrees 1.4 2.6 27.4 8.5
    15 A/C face only closed vent driver priority ECO cool fan speed 3/7 at LO 0.9 1.7 28.3 5.7
    16 A/C face only closed vent driver priority fan speed 7/7 at LO 2.5 4.3 25.7 14.3
    17 Rear defroster 1.1 2.0 28.0 6.8



    Conclusion: The biggest EV penalties come from (i) using heat at any setting or (ii) aggressive A/C. Conservative A/C use incurs up to a 5.7% penalty. All other heat or A/C tests that I conducted incurred at least an 8.5% penalty. In contrast, the EV penalties for using low-high beams or the heated seats or steering wheel were not as significant. Most of all, using DRL incurred the least significant EV range penalty, and so the balance between improved safety and lost energy is tilted in favor of using DRL for improved safety.

    Update 1:
    Going up a gentle hill on the highway, your engine speed may be 2000 RPM at 60 mph. Your equivalent current draw, according to ScanGaugeII, would be *roughly* 80-90 amps if you used EV Mode. This is equivalent to about 30 kW, or about 40 horsepower. At this rate, your electric range would be drained in about 10 minutes, and you would have gone only about 10 miles.
     
    #1 Skylis A, Nov 21, 2017
    Last edited by a moderator: Nov 22, 2017
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    Thanks for the write-up/table!

    Just for clarity, what's mid beams? (I assume night beams are low beams/dipped beam)
     
  3. bisco

    bisco cookie crumbler

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    why does heat cost more than cool?
     
  4. Skylis A

    Skylis A Senior Member

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    Mid beams is that setting between DRL and normal beams. I was too lazy to look in the manual to quote the formal name, but if you twist the lights switch on the left of the wheel two positions. It's slightly dimmer than normal beams which is the last position.

    By the way, this thread is so that if anyone else does their measurements, post them and let's compare numbers and methods. My guess is that heat and A/C numbers will vary seasonally, and by method of taking the measurement. It could also be because winter is coming so the car thinks that it won't need A/C as much. Or it could be that the resistive heating element draws a lot of power anyway. I leave that discussion to those who know more about heating elements and A/C compressors than I do.


    To measure the battery current and SOC in your Prime on your own with ScanGaugeII, I think that the following codes will work (posted a few places in PriusChat, also see ScanGauge website):

    Codes for battery current, then you can name it Bta or whatever you want:
    TXD: 07DF0153
    RXF: 432180000000
    RXD: 1810
    MTH: 000100018000

    Codes for state of charge, then you can name it SOC or whatever you want:
    TXD: 0747227A76
    RXF: C462057A3676
    RXD: 3008
    MTH: 006400FF0000
     
    #4 Skylis A, Nov 21, 2017
    Last edited: Nov 21, 2017
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  5. Tideland Prius

    Tideland Prius Moderator of the North
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    Ohh.. the parking lights? Yeah that runs the DRLs as well. (that's why it's dimmer).

    Thanks!

    Are you able to do the rear defroster? I think that would beat the headlights in amperage use.
     
  6. Skylis A

    Skylis A Senior Member

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    Rear defroster uses 1.1 Amps. Given the example of 15.0 amps over 30.0 miles, the EV Range penalty is 2.0 miles, or 6.8%.

    Due to the forum settings for this thread, I am unable to edit my initial post. Therefore, I am unable to update the table on the go as new readings come in, so you will have to just scan each post one by one to see IF there are further updates that I could add to the table. There is more information that I also meant to add to my initial post that I left out.

    Going up a gentle hill on the highway, your engine speed may be 2000 RPM at 60 mph. Your equivalent current draw, according to ScanGaugeII, would be *roughly* 80-90 amps if you used EV Mode. This is equivalent to about 30 kW, or about 40 horsepower. At this rate, your electric range would be drained in about 10 minutes, and you would have gone only about 10 miles.

    Charge mode varies too much to get consistent readings and depends on multiple variables, so no data from me on this.
     
  7. Tideland Prius

    Tideland Prius Moderator of the North
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    I'll update it for you :)
     
  8. Oniki

    Oniki Active Member

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    One of the advantages of PHEV over a BEV is being able to heat the cabin while in HV mode when the drive is longer than EV range permits. It is just now getting cold enough in my area to adapt this strategy and my drive into work today was my first time flipping into HV for cabin heating. It will be interesting to see how much my overall fuel economy drops this winter.

    Are there any smartphone apps that support the Prime ? I'd like to know engine temp
     
    #8 Oniki, Dec 4, 2017
    Last edited: Dec 4, 2017
  9. inferno

    inferno Senior Member

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    I always found the heating is more because of temperature variance.

    IE, I'm getting a huge hit on my EV range because of my heat...because it's 23 or so degrees outside and I want it at least 69 (so the car needs to up itself 36 degrees).

    Whereas honestly, in the summer, at 90...I'm comfortable with AC at 76 (or 80 sometimes!) to just dry the air, so that's a 14 degree difference and therefore theoretically half the energy.
     
  10. Oniki

    Oniki Active Member

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    The usual answer in cars is because heating is resistive while cooling uses a heat pump. The Prius Prime changes that rule of thumb somewhat because it has a dedicated heat pump for heating, but the pump efficiency rather quickly drops to resistance heater operation levels as the temperature approaches 20F or so.

    This is presuming that the source energy is always electric. In a plug-in you can game things sometimes by using ICE waste heat instead of battery for cabin heating. This is what I do on my long (more than EV range) drives to work: I heat the cabin when I am driving with a warmed up ICE.
     
  11. Oniki

    Oniki Active Member

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    I've now had two opportunities to mix EV charging with cabin heating from the ICE. I drive 90 miles total for my work commute, using one full battery charge and however much fossil fool as required. To keep my EV range as high as possible, I heat the cabin when the ICE is operating and warm. Drive temps are in 40s F one direction and in the 20s F the other.

    It is taking about one gallon of FF for the 90 miles. Obviously not as good as during warm weather but quite impressive.
     
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  12. bisco

    bisco cookie crumbler

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    i guess you would have to use the same temp differentials for heat and a/c to judge the efficiency of the heat pump.
     
  13. Oniki

    Oniki Active Member

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    You do not know from where on the efficiency curve you are deviating from, so the direction matters.
     
  14. bisco

    bisco cookie crumbler

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    can you explain more fully? i'm not that technically educated on the heat pump.
     
  15. Oniki

    Oniki Active Member

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    Think of it this way: would you expect a 5 degree cooling requirement to be the same from 80 to 75 as 150 to 145 ? It is the same amount of energy to displace, but the heat pump is just not very effective at high temperatures.
     
    #15 Oniki, Dec 7, 2017
    Last edited: Dec 7, 2017
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  16. bisco

    bisco cookie crumbler

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    thanks! so we would need the tech paper on the pump?
     
  17. Tideland Prius

    Tideland Prius Moderator of the North
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  18. bisco

    bisco cookie crumbler

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    thank you, but i did not see the efficiency ranges in either article. did i miss it?
     
  19. Tideland Prius

    Tideland Prius Moderator of the North
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    No. They're simply describing how a vapour-injected heat pump works. All that was mentioned is that Toyota said it uses 63% less energy and will provide 21% more range compared to other heating systems.
     
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  20. bisco

    bisco cookie crumbler

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    i'm trying to make sense of posts #13 and 15.
     
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