Thermal Effects on Energy Consumption and Range

Looking at energy consumption, right off the bat, we can see that cold weather has a significant impact on EC - nearly double in urban driving, 40% more in the highway cycle, and 25% on the US06. It’s worth noting here: the Leaf has an 80 kW electric motor, a 24 kWh battery, and a 5 kW resistive heating element.

When broken down further, into a base load case (driving cycle EC at 72F), the amount of extra energy needed to drive the cycle at 20F (listed as EC cold), and then the heater load required to maintain a cabin temperature of 72F, we can see that a significant portion of the additional energy consumption is down to the heater. As with most gasoline cars, driving in sub-freezing temperatures only makes the car about 10% less efficient before heater loads are considered. The mechanically-driven heating elements in conventional vehicles add another 5% or so in terms of mechanical efficiency loss, while obviously the electric heater in the EV is far more costly from an energy consumption standpoint even though it doesn’t increase mechanical losses at all.

(Note: graphs were created by ANL using the raw 10Hz data instead of the filtered 1Hz data available on D3. Available as part of APRF's AVTA Nissan Leaf testing analysis and summary, as presented by Dr. Henning Lohse-Busch. Full presentation available here.)

And while energy consumption is a big deal, range is the be-all, end-all concern for most consumers. With the heater on, that’s a decrease in range by anywhere from 20-50% depending on your drive cycle. That’s a lot. And you can just look at the APRF’s full charge tests at 20F and 72F to see what I mean: 

Think about that - this is a car that, at launch, Nissan claimed had a 100 mile range. My own real-world driving suggests 80-85 a decent estimate. EPA says that number is closer to 73. The APRF’s instrumented testing backs that up (74.1 mile range at 72F), but the same instrumented testing, in 20F weather? 46 miles. That’s it. 

Introduction and Technology Background How this Impacts the Model S & Final Thoughts
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  • Wolfpup - Thursday, February 21, 2013 - link

    Are they? Lithium ages even if it's not being used. I'd feel more comfortable with a NiMH battery pack in a vehicle like the Prius than with Lithium.

    What happened to super capacitors?
    Reply
  • Exodite - Monday, February 18, 2013 - link

    25-100% increased power usage at a mere -11C?

    I guess there's a reason no one here (northern Sweden) particularly fancies EVs. I shudder to think what the fuel economy would be like at -40C.
    Reply
  • Kjella - Monday, February 18, 2013 - link

    No, 20F = -6.7C so it's worse than that. Also I would assume this is the battery charge when they're new. I'd sure like to see tests on a 5-10 year old battery to see how reduced capacity and high drain go together. I suspect it would not be pretty.

    Here in Norway you get massive advantages from buying an EV (no one-time fee, no yearly fee, free toll roads, ride the bus lane, publicly sponsored charging stations) which is the only reason they've managed to sell a few thousand.
    Reply
  • Exodite - Tuesday, February 19, 2013 - link

    Yeah, I calculated from 20 rather than from 12. My bad. :(

    I could see EVs being used for something like inner-city taxi services in the southern end of the country but generally speaking both Norway, Sweden and Finland suffer from the same concerns here... cold climate and long distances.

    I'd rather see a quicker push into fully synthetic diesel solutions for us.
    Reply
  • elmicker - Monday, February 18, 2013 - link

    "the previous Top Gear vs. Tesla, which was an outright sham"

    Well, that's a libel.
    Reply
  • jonup - Monday, February 18, 2013 - link

    So was the lawsuit.
    What is so special about Model S? It's fugly and it feels like made in a shed. (I've been in one and it felt cheap.) Doesn't even stand a chance next to Fisker Karma. And just like the electric Elise before, it took on honest review to destroy the PR/artificially created fame.
    Reply
  • Azethoth - Monday, February 18, 2013 - link

    1) The model S is a sedan. You compare it with a Lexus or Mercedes sedan.
    2) The Fisker Karma is a sports car. You compare it with a Porsche or the Tesla Roadster.
    3) The review was in no way honest. Major egg on his face and NYT face.

    Your post is bizarre. Do better in the future.
    Reply
  • jonup - Tuesday, February 19, 2013 - link

    Fail on this one alone:
    /quote 2) The Fisker Karma is a sports car. You compare it with a Porsche or the Tesla Roadster. /quote

    Both Model S and Karma are 4-door sport sedans. Except one is fugly and the other is gorgeous. Tesla Roadster is what the name says.

    I really don't get your first point. Are you arguing build quality?! I've been in one and it was as refined as... refined and Tesla Model S do not belong in the same sentence.

    They tore apart the guy that gave objective review of the POS Chrysler 200. It beats me how car companies have better PR than newspaper.

    You know what, forget what I wrote. Go get yourself a Model S with a big touch screen "tastefully" slapped in the middle. It seems to impress most people.
    Reply
  • Activate: AMD - Tuesday, February 19, 2013 - link

    "Except one is fugly and the other is gorgeous."

    Thats your opinion, don't pass it off as fact. I personally think the Fisker looks like the sick offspring of a Maserati and the Cheshire Cat from Alice in Wonderland.
    Reply
  • Spunjji - Tuesday, February 19, 2013 - link

    Don't let your logic get in the way of a fan-boy rant ;) Reply

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