• Feb 1st 2011 at 11:53AM
  • 35
The Ford Fusion Hybrid and its sibling, the Mercury Milan gas-electric, have failed, on numerous occasions when driven in cold weather, to return gas mileage results that match their EPA rating of 41 mpg city/36 highway. Likewise, the Mini E's usable range, when driven by Dr. Lyle Dennis, dropped substantially as the mercury dipped down to 23 degrees Fahrenheit. Heck, even General Motors admits that the Chevy Volt's electric-only range will likely degrade as winter sets in and we're fairly certain that the Nissan Leaf is not immune from bitter cold temps. So, what causes a battery's performance to degrade as the mercury drops?

Bryan Johannsen of The Car Electric, a pro-plug-in vehicle site, summarizes the chemistry that causes batteries to suffer in the cold:

All batteries deliver their power via a chemical reaction inside the battery that releases electrons. When the temperature drops, the chemical reactions happen more slowly and the battery cannot produce the same current that it can at room temperature. A change of ten degrees can sap 50 percent of a battery's output. In some situations, the chemical reactions will happen so slowly and give so little power that the battery will appear to be dead when, in fact, if it is warmed up, it will go right back to normal output.

Johannsen concludes with this bit of advice:

Cold has a negative impact on all aspects of battery operation. Keep this in mind if you're planning an electric car purchase; we don't want you finding out the range of your car has been halved when it's five below zero and you're fifteen miles from home.

While gasoline-fueled vehicles are not invulnerable to the effects of cold weather, electric-drive cars are where the decreased efficiency is most noticeable when the bitter temps set in.

[Source: Washington Post]

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    • 1 Second Ago
      • 8 Months Ago
      The article is quite accurate. This is why Nissan will offer a cold weather package for the LEAF. It will be able to pre-heat the battery pack as well as the cabin when the vehicle is plugged in.
      • 8 Months Ago
      I still get 46 in a hybrid with snow tires in subfreezing temps for several mos. and idling is wasteful and useless. I also tow bike and get 48 in summer on stock 'eco' tires. I dont do some hypermiling bullshit either. most americans dont give a **** anyway..gas needs to go to five bucks since 'christian' ethics and morals doesnt apply to altruism or saving planet or giving a **** about anybody else on planet.
      • 8 Months Ago
      50% change with 10 degree difference? No way. My 50 mile unheated pack still gives me 40 miles in 30 degree weather. Insulate and preheat the pack when plugged in to limit that reduction.
      • 8 Months Ago
      Where is a flux capacitor when you need one?
      • 4 Years Ago
      If only there were some electrochemical reaction that was exothermic, and could reliably power an EV in extremely cold temps, while not dramatically losing range due to the need to keep the passengers comfortable.

        • 8 Months Ago
        And yes this is another challenge (not insurmountable) for the northern climate. What to do with your BEV at -40 deg C/F sitting in a parking lot. The options

        1) don't buy an BEV in the first place
        2) consume what little voltage you have to increase the temperature of the battery
        3) use emerging technology that doesn't depend on temperature as much
        -Estor or other ultra capacitor
        -Potentially Fuel cell (although H20 is a solid at -40 C/F which will foul your plates quick with frost, you might be better off with a Ethanol based fuel cell for these conditions)
        4) use mature technology that is tested
        - Diesel
        - Gas/electric hybrid
        - biofuel
        • 8 Months Ago
        LOL I see where you're going here... (fuel cell). Well, let's see how long before the BEV fanatics start calling this article a lie and start spouting their 'truth' - that batteries have no weaknesses at all and it's a big conspiracy theory of the evil corporations.

        Oh and since I used the words fuel cell, let's see how long it takes people to start railing against that technology too!
        • 8 Months Ago
        I wouldn't assume fuel cells and ICE don't get affected by the cold either, or that fuel cells will have less of an affect than an ICE.

        Batteries are exothermic reactions too, except not as many losses go to heat due to their efficiency (so instead we use the energy we save to go to a heater instead).
        • 8 Months Ago
        "I wouldn't assume fuel cells and ICE don't get affected by the cold either, or that fuel cells will have less of an affect than an ICE."

        I haven't assumed anything. FCVs have proven their reliability (starting capability and operational range stability) down to some pretty extreme temps.

        The Toyota FCHV-adv is operational at temps to -30*C.
        The Mercedes F-Cell has been proven in tests in Sweden to operate in -25*C.

        Of course, we've gotten off topic. This article wasn't intended to be a discussion of FCVs, and we should focus on the issue of BEV performance in cold weather conditions.

        I do agree that as batteries get larger, cold weather degradation will be less of an issue. Like wise, preheating a BEV while still connected to the mains is an ideal solution. Block heater plug-in stations are already commonly accepted in areas that deal with extreme cold temps - people are already well-conditioned to remember to plug in their ICEs.

        Still, it would be nice to develop battery chemistries that were more stable over a greater range of temperatures. Maybe in the future, there will be "cold-climate" batteries and "hot-climate" batteries that the buyer will specify based on their anticipated needs.

        • 8 Months Ago
        You missed a couple of options:
        -keep it plugged in like most block heaters.
        -use a cell chemistry that has operating temperatures at that level (a123, altair-nano).
        -keep the battery well insulated and use only liquid heating and cooling to maintain storage temperature (like the Tesla, which can park for weeks with a fully charged battery)
        -allow the battery to get cold and "thaw" it when you have to use it (some Tesla owners do this).

        It's not as big a problem for batteries as you people are trying to make it to be. And the significance will be lower as BEVs start carrying more energy onboard. Heating requirements scale by time, so for an average 4kW heating load, on a 1 hour trip it will use 4kWh. This is 25% of the battery for a 16kWh battery like on the Volt or the iMIEV and 17% for the Leaf's 24kWh. However with a ~200 mile EV, it'll only be 8%.
        • 8 Months Ago
        Voltage drops as the temperature plummets. Those who live in climates where it matters know this already - the energy to turn over the motor is reduced when it is cold, and you may not be able to start the car without a boost if you are not fully charged.

        Battery chemistry is exothermic overall - as you drive you will be heating the battery just from use, if for no other reason that the battery has internal resistance. If you have preconditioned the battery this may be enough to keep the temperature up in cold weather. Otherwise you may have to waste some energy heating the battery to keep the voltage up (either electrically with a resistance load either within the battery or into HVAC fluid or just cabin air eg Leaf, or launching the ICE eg Volt) all of this reducing your range.
      • 4 Years Ago
      "A change of ten degrees can sap 50 percent of a battery's output."

      Knowing what temperature this occurs at would be helpful. And is this Celsius or Fahrenheit? A change of one degree Celsius is almost twice as much as one degree Fahrenheit.
        • 8 Months Ago
        The degree of drop off is highly dependent on the battery chemistry.
        For cold weather use you ideally want a lithium titanate technology, which is fine down to -30C.
        Here are the performance graphs for Toshiba's:

        Down at the bottom right you will see mention of their 20Ah technology which they are to build for cars this year.
        It has an energy density of 100kwh/kg, a lot lower than some other technologies but just about workable in cars and fine for the Proterra bus it is used in.
        Toshiba hope to bump that up to 150kwh/kg.
        Altairnano also build lithium titanate batteries, in fact that is the one in the Proterra.
      • 4 Years Ago
      Hi, I am from India and an avid watcher of the electric car seen. The more i have read, the more i am convinced that an electric car is made for our country. We have a temperate climate with temperatures hovering between 10 degree centigrade to 45 degree centigrade.
      Our average speed of driving is sixty kilometers per hour. Our average commute is around 30 to 40 kilometers. Also we have slow moving traffic with a lot of stop and start.
      Our safety regs are pretty much voluntary, so cars can be made a lot lighter. We seldom need to travel between cities and when we do we usually take a bus or a train. almost every part of our country is connected by trains although plane travels are increasingly being popular. quite a lot of our train routes are fully electrifies.
      It would take a much lighter battery pack to propel us 150 kms, also the car can be offered in basic trims so it could be done much cheaper.
      i wish one comes very soon as i would buy one as soon as one lands here. :)
        • 8 Months Ago
        I have visited India, my concern with EVs in India is the infrastructure. Does india have the ability to provide electricity for large numbers of EVs? Also, where to charge? Other than that I agree India would seem to be ideal. Having braved Mumbai traffic, any noise reduction would be very beneficial.
      • 4 Years Ago
      My commute to work is 18 miles round trip, no highway. My Fusion Hybrid gets at the very least 36 mpg in the winter and 43 mpg in the summer. Yeah that's 36 mpg in single digit weather, I pay attention to how i am driving but i am not obsessed with hypermiling. Long term fuel econ is currently 40.2 mpg over 2 years. I live in Colorado. Love this car.
      • 4 Years Ago
      It has been a while since chemistry, but what I don't understand is why a battery's energy drops so quickly with temperature.

      For example, many of the physical laws are based on the Kelvin scale which I think is 273 degrees at 0 degrees C (and 1 degree Kelvin = 1 degree Celcius). If that is the case, the % change in temperature is not nearly as large as the loss in energy.
        • 8 Months Ago
        The stored energy doesn't drop, the rate at which the energy is released drops.

        The reduction in range comes from the increase in internal electrical resistance in the batteries when cold, but since that same resistance also warms the batteries, the effect is limited and the range reduction relatively small.
        • 8 Months Ago
        The rate that a chemical reaction occurs at, is generally found to have an exponential relationship to the temperature.
      • 4 Years Ago
      I like Volvo's solution, to use an Ethanol heater. A fuel burning heater (ethanol, propane, gasoline, whatever) could be used to keep the battery pack warm while not plugged in, heat the cabin and even the seats directly. A sophisticated design would be to heat water and with a pump, some valves and some relatively simple control scemes, it could share water loops that are also used for cooling to keep the battery and the cabin at desired temps. A more simple design would be to have 2 separate fuel heaters; one for the cabin which would be an air to air heat exchanger and one for the battery pack which would be air to water for most EVs or air to air for air cooled designs like that on the Leaf or EVs with swappable batteries. The big issue that I see is that a fuel heater could cause CO problems when parked in enclosed spaces. They could use a CO monitor or only enable the heater to run when the ignition switch was on. It would be no different than a building's HVAC system, which I design. Anyone want to hire me?
        • 8 Months Ago
        Or just chuck the whole electrically-powered idea and use the (renewable, in that case) liquid fuel in a combustion engine. If you're going to have to burn fuel anyway, you might as well get some mechanical work out of it ...
        • 8 Months Ago
        @Brian P
        Except using fuel for propulsion is much less efficient than using fuel for heating (almost 80% of energy from fuel goes to heat in a typical ICE). The only reason they are even considering fuel for heating is because it is an efficient way to heat.
      • 4 Years Ago
      I think it's important to note that the battery still holds it's full charge worth of energy, the battery is just too cold to release it's energy.

      Therefore, it seems that those EVs that can heat the battery (e.g. the Ford Focus Electric) should have a significant advantage over EVs that's don't (e.g. Nissan Leaf).
        • 8 Months Ago
        yes and a bit of insulation means you don't have to spend significant energy heating the pack. cold will not be a problem in the long run.
        they just have to learn that batteries shall be inside the car, not out.
        • 8 Months Ago
        "it won't do you any good at 5PM in the middle of a 20°F office parking lot."

        Except it will, I think that's his point. When you start out in that parking lot, your range might be, say 15 miles, but as the battery heats up while you're driving it back home, that range will start to go up, and could eventually end up at 30 miles. If you can't heat the pack, you won't get any warmer no matter what you do. If you can, you'll be able to slowly increase your range just based on how hot the battery is getting.
        • 8 Months Ago
        We don't know how general those results are and it doesn't explicitly point to the Leaf.

        Looking at the driving profile, the driving miles was only 16.5 miles per trip, before an extremely long 8 hour resting period in between. With this driving profile, the range isn't even going to matter that much. The results would be extremely different with a longer trip where you start to have to worry about range (and a longer trip will probably show a larger difference between liquid cooled and air cooled batteries).

        The driving profile will play a huge role in the percentage affect. So you definitely can't take the percentage numbers as a general case.
        • 8 Months Ago
        Evan, one question is how much energy does it take to heat the battery to a reasonable level of efficiency? Once on the road (say at 0F), how quickly will the battery cool? Then as Berk said, it sits in a parking lot for 9 hours.

        Where I live, it gets plenty cold (about 5F right now). For me something like the Volt makes more sense. I wonder if the Volt could use all that excess heat from when the ICE is running to warm the battery? Hmmm, I gotta make a quick call to GM. :)
        • 8 Months Ago
        Very true. However, while the self-heating batteries may help you in the morning before you disconnect the plug and head to work, it won't do you any good at 5PM in the middle of a 20°F office parking lot.
        • 8 Months Ago
        But if you check Volt ev range being reported, it seems to be taking a large cut - even with heated batteries. Same as Leaf.

        NREL published a recent study on this - you can see links to the study here.

      • 4 Years Ago
      Good article, I'm no battery expert, nor do I really strive to be one, so I always wondered what the limiting factor was when batteries got cold. I just experienced this phenomena this past weekend with my camera battery. Being outside in 0 F weather for hours on end caused the indicator to drop very quickly, but after warming the battery it in my jacket pocket for an hour or so, I was good to go again.
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