Tuesday, February 26, 2019

Just How Bad Was the Cold on Electric Cars?

Back during the strong cold snap a few weeks ago... sorry, let me turn on the reverb, during the Po po po lar lar lar Vor vor vor tex tex tex ...  there were stories about how badly batteries were affected by the cold weather.  So how bad was it?
AAA recently studied the effects of cold on EV range and found that when temperatures dropped to 20°F, EV (electric vehicle) range dropped an average of 41% compared to range measured at 75°F.
It does freeze in my corner of the planet, but not very often.  I think the last day we had when it was under 32F around here was in 2010.  Still, I realize that freezing happens on much of the earth and I don't think a fuel source that loses half its capacity in the cold is something I'd be trying to stake the future on.  Perhaps the bigger problem is that it's not only worse in the cold, it's worse in the heat, too.  The range vs. temperature curve is shaped like an upside down "V".
 AAA tested five electric vehicles, all with a minimum EPA estimated driving range of 100 miles, in partnership with the Automotive Club of Southern California’s Automotive Research Center. For this study, AAA researchers used a 2018 BMWi3, a 2018 Chevrolet Bolt, a 2018 Nissan Leaf, a 2017 Tesla Model S 75D, and a 2017 Volkswagen e-Golf.

The BMW i3 was most sensitive to temperature change in both hot and cold conditions, losing 50% and 21% of range in cold and hot conditions, respectively. The Nissan Leaf was the most temperature-resistant, losing 31% and 11% of range in cold and hot conditions, respectively.
All the cars had between 1,000 and 6,200 miles on them before the test, and all of their battery packs were tested to rated limits before and after the tests.  Tests were conducted on a dynamometer in a temperature chamber.  No warning lights were allowed before or during the test runs.  Lots of details for how they were tested on the Power Electronics magazine article's website.

The striking difference between the BMW i3 and the Leaf makes me wonder what the two companies did differently.  If one car is significantly different from the others, why?  What did the bad one do wrong or the good one do right?  Can we make them all like the good one?

I hope it's evident that hot weather is a problem, too.  Just as running a heater when it's 20F outside sucks battery life and vehicle range, when it's 95 outside and you're running the air conditioner, that sucks battery life, too.  Of course, the air conditioner puts some load on gasoline consumption, while most internal combustion engine cars use at least some waste heat from the engine to warm the cabin, too.  With an EV, everything has to come out of the battery. 


  1. My next door neighbor has a Leaf.

    In good ("Happy Battery") weather, it goes 100 miles.

    A trip to Denver requires charging while there, and stopping to eat on the way back while the car gets some more charging.

    He has to plan his trips carefully if he's going out of town. He has no problem driving around the city here, as there's public fast chargers all over the place.

    Drive to Nebraska? Sorry, can't make it.

  2. Hybrids may make some sense, I guess. I have never owned one and have no plans to acquire one.

  3. Charging a Frozen Li-ion battery is also a problem. Trying to charge a Li-ion battery that is froze will damage it, reducing the charge capacity and making them subject to explosion in the event of "mechanical vibration". Which would be bad, since I think most cars are subject to some vibration, even before they hit a pothole. (Something you get a lot of in my part of the world.)

    1. It's really a double whammy that renders the EVs essentially dead if extended cold happens.

      It gets 2/3 the range (I'm being generous) and can't be recharged. So when it's below freezing long enough to use up its charge and the owners end up with a non-rechargeable battery, now what? I can imagine cars dying in traffic and having to be towed. If you're stuck in your car when it's below zero, that's a life-threatening situation. It will be incapable of generating heat.

  4. I hear Generac is coming out with a line of trailers.

  5. I guess this is a reminder to dust off my annual rant RE: semi-electric cars.

    I realize electric cars is a religion and diesel is a four-letter word, but....

    Electric has its positives, but they are few (40 years ago Brock Yates of Car&Driver said "electric cars are great if your goal is to run cars on coal."). Same for the dreaded diesel, except the negatives are more controllable and the positives are bigger than electric's. A small turbo diesel (side note: I detest the current trend of shrinking engines for weight reduction and then using turbos and 9-speed 2-clutch awfulmagic trashmissions to get the power and drivability back; those engine systems will not last long) can deliver stunning levels of efficiency when confined to a narrow RPM operating range. Which is true of any reciprocating internal combustion engine; look at racing engines; lots of horsepower, narrow power band (old joke from motorcycle road racing in the '80s: "Know why the Yamaha TZ350 has a 6-speed gearbox? Because the AMA rules won't let them put a 15-speed on it." The TZ350 was a giant killer if you knew how to ride it.)

    Anyway, the small highly efficient turbo diesel driving an alternator can easily provide 110-115% of the necessary motive force for "normal" operation and the system can use a small battery pack for those times more is needed. The electron surplus charges the batteries during "normal" mode. Running with motors at the drive wheels means no transmission is required, nor driveshaft nor differential, so weight gain from heavy motors balances out with dumping the trans and diff.

    And, if one gets the night terrors over diesel, small gasoline (or, for that matter, propane) engines can be quite efficient as well (although not to the level of diesel, just because of the BTU/gallon thing - 128K for diesel, 116K for gasoline, 94K for propane).

    An engine operating at a single RPM is easier to control for efficiency and emissions because everything from the intake tract, ignition timing (for gas/propane), valve timing, to exhaust, etc. can be designed for maximum efficiency rather than operational tractability.

    But efficiency has never been the driver behind electric vehicles because religion.

    Random Thought: I wonder if there are lawyers looking at specializing in wrongful death suits over electric cars that kill their owners because of weather based operating restrictions.

    1. Good summary.

      There is simply no substitute for fossil fuels in terms of energy available for a given mass. Gasoline is a mix of light molecules so it doesn't freeze in "normal" cold temperatures - it has to be well below zero.

      The inefficiency of the IC engine that greenies rail against is a feature in cold weather. It's not a feature in my world, except maybe for a week out of a year, but I can't see how all electric cars could be useful for anything without the petroleum infrastructure.

    2. and... following up to your caring for your li-on battery post:
      charge to no more than 80%, recharge before 30%, you have a 50% "tank" before you start factoring in the ambient temperature issues...

  6. I would suspect a significant part of the Leaf vs BMW difference is the BMW is more sporty and puts a higher load on the battery during accelleration because it can actually accellerate vs the Leaf with its lower power output keeping max draw on the batteries at a lower level.

  7. Re-reading my comment, I realize I forgot to mention the cold weather problems with propane: propane boils at any temperature above -44F, but as it gets colder - as in "below about +15-20F" - the vaporization rate declines enough to require some attention. As a rule that's not a problem, but using propane as a home heating source much above about 40 degrees north latitude can become problematic Dec-Mar, and is the reason for the existence of propane tank heaters in northern climes. That means "add energy input to the storage system to get energy out" which is the problem with Li-ion batteries, but not to the same degree.

    And, my memory is fuzzy, but IIRC diesel fuel begins to gel somewhere below +16-18 F ("gel" simply means the waxes in diesel crystallize and settle out; whatever you call it, it means engine no workee good, maybe no workee at all, unless there are additives to prevent the gelling). Also IIRC, gasoline remains fully functional to about -50F. So we're back to requiring the rapid oxidation of deceased dinosaurs to get to work. Funny how it seems we always wind up circling back to hydrocarbons - specifically, refined hydrocarbons, as in "gasoline" - being what works, despite the most fervent wishes of the Lefties. Maybe there's some Great Secret About What Actually Works being denied to Elon, Bernie and Alexandria.

    1. Excellent stuff.

      I've read there are mixes of gasoline that get you to -50C maybe -60C. That covers pretty much anything you find in Antarctica or Siberia. There's a place in Siberia where manufacturers bring aircraft to test because it gets the coldest temperatures on Earth - I think it's Oymyakon, by lookup. It has been to -90F. I don't know what they use for fuel or if they're even anything they could use.

    2. Last sentence - the result of changing while writing from " I don't know what they use for fuel or if they're even trying to run" to " I don't know what they use for fuel or if there's even anything they could use."

  8. I concur that electric hybrids will be far superior to pure electric vehicles, barring a revolution in battery technology.
    Electric power from thorium nuclear plants is sustainable for many centuries at 1960s tech level, let alone what we are capable of today. Small, efficient, internal combustion range extenders fueled by woodgas, biodiesel, or ethanol can make up the shortcomings of EVs while being relatively low-impact from an environmental standpoint.

    Unsurprisingly, .Gov mismanagement has torpedoed nuclear development and made a bureaucratic boondoggle of biofuels, so we're left with the old standbys of fossil fuels and smug liberals who don't understand how electricity happens to show up at their outlets.