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Energy usage spike in traffic

Discussion in 'Canada' started by mibaro2, Aug 7, 2014.

  1. mibaro2

    mibaro2 Member

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    I was caught in traffic Monday night when the 407 and QEW were closed. I was driving from Hamilton to Georgetown which is not that far. It took 3 hours to get home, 2.5 hours creeping along the QEW to Walkers Line. What is interesting is the energy spike that the car used to go 10 km in bumper to bumper traffic. A/C was off.

    Here is a blurry photo of the spike :

    energy spike.jpg

    Thought I would share it. I did make it home with plenty of charge...eventually.
     
  2. rapoport3a

    rapoport3a Member

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    Yesterday I crept along 401 going west into Kitchener from Cambridge but didn't spike that much. Wh went up but not much. Why, do you think, your use spiked by that amount?

    Going back to Hamilton the Wh went down to 150. I was surprised, although there is a descent.
     
  3. mknox

    mknox Well-Known Member

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    I've seen that from time to time as well. Did you have the a/c on? I think the a/c or heat power draw averaged over fewer miles (because you are going so slow) is what causes this.
     
  4. mibaro2

    mibaro2 Member

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    Glad someone else has seen a spike like that.
    If I did have the a/c on, it was set to a higher than normal temperature. Next time I'll remember to turn it off. I wonder if the 17" screen uses much power (refreshing gps).
    Hand-in-hand with the spike was my watts/km jumping... it went from 160 to 210 . I expected that since I wasn't moving.
     
  5. mknox

    mknox Well-Known Member

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    There was a thread a while back about a guy who had his car in to a tire shop and noticed this when he got the car back. He assumed they had taken it for a joy ride. What it turned out to be is that the car was sitting on the hoist with the door ajar and the HVAC running or something like that. Remember this graph is showing Wh per mile (or km) so if you are consuming power, but not moving very far, the graph will go up.
     
  6. brianman

    brianman Burrito Founder

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    Yah, small divisors have superpowers at times.
     
  7. JohnQ

    JohnQ Active Member

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    Might have been battery cooling kicking in?
     
  8. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Passive battery cooling (fan only) kicks in a 40˚C and active cooling (heat pump) kicks in at 48˚C. That's getting pretty hot, but it can happen.
     
  9. green1

    green1 Active Member

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    the OP stated it was in stop and go traffic, my guess is that the energy usage per km gets really high when you're moving zero km but not using zero electricity....
     
  10. mibaro2

    mibaro2 Member

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    Makes sense.
     
  11. PoweredByRain

    PoweredByRain Member

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    The other major factor, I think, is what you do with the kinetic energy you do have. There's a huge difference between traveling at say 10-20 km/h with regenerative braking versus frequent actual stops that require the use of friction brakes. Every time you use the brakes you are throwing away all that energy. When you use the regenerative brakes you are getting back most of it.

    I have been in "stop&go" traffic that for a time was actually moving fairly well at 6-10 km/h, on level ground and with little need for climate control, and the car managed about normal "rated" energy usage. Had I tried to go 15 km/h then stomped on the brake to zero then tried to go 15 then stomped on the brake, etc, then energy usage per unit distance, I bet, would have doubled.
     
  12. Newscutter

    Newscutter Member

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    I also F-REAKED the first time I saw this. Took a pic! Then I realized the same thing... PER MILE. Mostly stopped traffic (plus AC/stereo) makes for a lot of power per mile.

    tuesday+6-24-2014+11-21-44+AM.JPG
     
  13. yobigd20

    yobigd20 Well-Known Member

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    Battery cooling kicking in. That's one reason not to drive it down near 0 because cooling can kick in at any time and steal the rest of your range away from you leaving you stranded all of the sudden.
     
  14. DITB

    DITB Charged.hk co-founder

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    Well, imagine what it is for gas and diesel cars. Even if they are completely stopped, they will still be idling away - unless they have stop-start automatic engine control. Since the Model S has so precise energy monitoring, it seems a lot, though nothing compared to ICE cars. I wonder if TM will make some kind of traffic jam power saving mode? It's easy to slow down to increase your range, but not much you can do if you are stuck in traffic. Imagine you run out of power for that reason, that must be frustrating. And there is no manual turning off of the screens and some other equipment, the best you can do is to keep radio and A/C off (but I doubt the radio will matter much).
     
  15. gavine

    gavine Petrol Head turned EV Enthusiast

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    How do you turn the radio off?
     
  16. DITB

    DITB Charged.hk co-founder

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    Sorry, I don't get my car until mid September. I just presumed you could turn it off? Anyway, it's probably not the radio that kills the range, but rather air con, battery control and general car operation, screens and so on.

    This is from the roadster, probably similar for the Model S

    Tesla_Wh_breakdown.jpeg
     
  17. green1

    green1 Active Member

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    By definition, a stopped car uses infinite energy per km, because it moves zero km, so even if all it has on is a single tiny LED, it will still use infinite electricity per km. At a stop the proper measurement is per minute, not per km. Now most vehicles stop displaying if you are actually completely stopped, but if you are creeping along at 0.1km/hr or something then you'll get a very similar effect, where your energy use isn't quite infinite, but is still extremely high on a wh/km basis.

    What you can do though, is most stop and go traffic is only that because nobody leaves any space, often you can back off from the car in front of you a bit, and cruise at the average speed continually (eg. instead of going 20km/hr-0-20-0-20-0 constantly, you can back off a bit to give room, and drive at a constant 10km/hr.) It's much more efficient, and generally less frustrating too. (you just need to give yourself enough space to even out the pattern)
     
  18. DITB

    DITB Charged.hk co-founder

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    Totally agree on this technique. Unfortunately, it is often ruined by people who keep swapping lanes, trying to "climb the ladder" in the queue, treating it like a step machine in a gym. It's the same for ICE cars, holding a constant slow speed is better than start-stop, although in any case, very low speeds are inefficient just like very high speeds, no matter how your technique is.
     
  19. Newscutter

    Newscutter Member

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    Like I said before-- when I took the picture I was in "oh no it's BROKEN!" mode and wanted to document it. While I'm not the OP, I shared his experience.

    After a few minutes of studying the graph I came to the same realization as has been expressed here, the PER MILE axis is what it is important.

    I don't think crazy low-power modes are necessary (in stopped traffic surrounded by hot ICE engines the last thing you'd want to do is eliminate the AC or roll down windows to enjoy their exhaust). Rather, further education for owners (especially NEW ones like I was-- who have never had a Tesla rep explain their car's functions/features, but had it dropped off in a parking lot) that-- and here's the key in my messed up sentence punctuation-- <drumroll>:

    Despite a prolonged energy spike on the graph, the RATED RANGE did not drop. Not a single mile. The car made all sorts of scary loud noises and fans and commotion and the graph spiked... but that was all just paranoia-inducing as the actual range remained linear.

    So... watch that instead. And turn up the music to drown out the noise.
     
  20. green1

    green1 Active Member

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    I don't yet have a Tesla, but I'm assuming that, like most cars, it zeros out that graph when truly stopped or parked (otherwise the spike would be expected by all drivers) so perhaps what they really need is to just tweak that algorithm a bit to zero it out at a slightly higher speed (say 5km/h or something) so that people don't see the spike.
    (I agree customer education is best, but it's also less likely to succeed)
     

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