Batteries EV battery range extender

Published on January 21st, 2016 | by Tina Casey


All-Climate EV Battery Range Extender Goes From -22 to 32F In 30 Seconds

January 21st, 2016 by  

Did you know that conventional lithium-ion electric vehicle batteries can lose 40 percent of their capacity in cold weather? That’s an extreme example, but capacity loss during cold outdoor temperatures is a big issue for electric vehicles. Not to worry — it looks like researchers at Penn State University are on to a cure that could enable EV owners to warm up their cars to optimal battery conditions in a matter of seconds and keep them there, with only a minor loss of capacity.

EV battery range extender

Cold Weather And EV Battery Range

The basic challenge is one that is common among older gasmobiles, which require a longish period of idling after starting up in cold weather, in order for the engine to operate efficiently. That problem has long been solved by gasmobile manufacturers, but EV battery design is still playing catch-up. EV batteries have an optimal operating range, so if your EV has been sitting for a while in cold weather, you need to expend some amount of capacity to warm it up, to keep it warm while driving, and to keep yourself comfortable as well.

With a ripple effect of reducing the input from regenerative breaking, the result can be a loss of 40 percent in EV battery range or even more, according to Penn State researchers.

Last year our sister site passed along some cold weather driving tips for EV owners, courtesy of BMW i3 blogspot, which emphasize that cold weather driving involves some degree of careful planning and foresight because of the drain on battery capacity.

A New York Times reporter notoriously found that out the hard way right around this time in 2013, when he attempted a long distance drive in a Tesla from New York City to Boston in the dead of winter.

The episode evoked a thunderstorm of disapprobation from Tesla Motors owner Elon Musk, as it appeared that the reporter deliberately failed to observe common sense, but it gave CleanTechnica a chance to point out that the real issue is the cost of EV batteries.

Coincidentally, 2013 was also the year that President Obama’s EV Everywhere initiative took on the issue of EV affordability with a whopping $45 million round of funding for EV tech, including improved EV batteries.

In October 2013, Penn State announced that it received a piece of the EV Everywhere pie, in the form of a $3 million grant that teamed it up with the lithium-ion battery company EC Power and these other folks:

The two-year grant from the DOE’s Vehicle Technology Office supports the project “High Energy, Long Cycle Life Lithium-ion Batteries for PHEV (plug-in hybrid electric vehicles) Applications.”

Penn State serves as the main principal investigator (PI) on the grant, with the University of Texas at Austin and Lawrence Berkeley National Laboratory as co-PIs. Also partnering on the grant is the Argonne National Laboratory and industrial power products firm EC Power.

That’s some pretty fancy firepower, right?

EV Batteries Warm Up From -22 To 32 In Seconds

That brings us right around to the new EV battery warmup solution from Penn State and EC Power.

The team started with existing patents from EC Power and developed an “all-climate” lithium-ion battery that incorporates a thin (50 micrometers) foil of nickel. One end is attached to the negative terminal and the other goes outside the cell, effectively creating a third terminal.

With an assist from a temperature sensor, electrons automatically flow through the nickel foil when the battery temperature drops below 32 degrees Fahrenheit. That translates into heat for the foil, which flows into the innards of the battery. The heating system automatically shuts itself down once the battery temperature achieves 32 degrees.

While the new battery would weigh (and cost) slightly more than one without the nickel foil system, the numbers work out much better in terms of range extension, and the system practically eliminates the need for an extended warmup time:

The researchers, relying on previous patents by EC Power, developed the all-climate battery to weigh only 1.5 percent more and cost only 0.04 percent of the base battery. They also designed it to go from -4 to 32 degrees Fahrenheit within 20 seconds and from -22 to 32 degrees Fahrenheit in 30 seconds and consume only 3.8 percent and 5.5 percent of the cell’s capacity.

You can get all the details on the new all-climate EV battery from the journal Nature, under the somewhat modest title “Lithium-ion battery structure that self-heats at low temperatures.” The authors note that in addition to EV batteries, the new system could prove useful for robotics and space exploration.

EV Everywhere: Thanks, Obama

The research team also notes that a number of other materials could work as well as nickel, but the idea was to focus on the least costly material that could do an effective job, a goal supported by EV Everywhere. It’s quite possible that some auto manufacturers would go for the most efficient material regardless of cost, depending on whether or not affordability is a critical issue for their customers.

With that in mind, let’s catch up on EV Everywhere. The initiative is designed to make EV ownership just as affordable and convenient as owning a gasmobile, and it looks like things are heading in the right direction.

In addition to EV battery research, EV everywhere includes lightweighting initiatives to extend battery range

EV Everywhere goals

…and one of our favorites, the Workplace Charging Challenge:

workplace EV chargingCombined with enough range to last through the weekend, workplace charging is a good solution for many potential EV owners who don’t have access to an EV charging station at home.

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Image credits: top, all-climate battery via Chao-Yang Wang, Penn State; bottom two via US Department of Energy

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • Riely Rumfort

    As I see it these are highly advantageous for renewable storage. Heat fluxation causes fissures in batteries lowering capacity. In cases of BMSs regulating voltage based on thermal sensor the batteries could instead dump the power directly within the cell to keep in the optimal tempurature range when cold or stabilize them indefinitely. Furthermore a group of such batteries could be room heaters in a liquid volume if desired, keeping many in a brick of blocks at 70-75 degrees could warm a room without damaging the batteries if near constantly retained. Though for ultimate longevity you’d want to keep them between 40 and 65. Still though I think they’d make a nice thermal sink. Regularly transferring power out of a battery loses 5-25% of the charge, so direct to heat could be more efficient as far as energy conservation goes.

  • Tesla uses heat produced by the large AC motor (powering the wheels) to transfer to heating the battery conditioning loop. This makes the Tesla more efficient than my much much smaller Smart ED on the same trip. Driving a Tesla long range in the winter is interesting as you can witness all of the various battery management systems and techniques via the variety of feedback signals such as the way the energy usage drops considerably over time, even with cabin heating off, plus the way the regenerative braking system allows progressively more energy recovery as the battery warms up.

    • Steve Grinwis

      Your Smart has the AC motor in the same coolant loop as your battery, just like the Tesla, AFAIK.

  • Steve Grinwis

    This whole thing is basically a farce… It’s an electric resistance heater.

    And we’re comparing it to other electric resistance heaters, and it comes out an order of magnitude better? Ya. This is mostly bullshit, and that’s your first clue.

    We need to understand why we lose range in the winter. There are a bunch of reasons:

    1) Use of cabin heating / Heated seats
    2) Use of windshield wipers to clear snow / water from roads / Window defrosting
    3) Use of winter tires / cold tires which have higher losses
    4) Less than ideal road conditions in general
    5) Air density increases in cold weather increasing aerodynamic losses
    6) Battery is somewhat colder, which marginally decreases capacity

    The big one here is actually cabin heating. at -5C, I can’t actually tell the battery is cold in my electric, and I can get pretty close to the same range, if I don’t run the heat. This is without battery heating, or pre-heating.

    Heating batteries is only really necessary when it’s required for the batteries to discharge without damaging themselves.

    The other issue here is they’re comparing a single instantaneous impulse of heat to an hour long drive in terms of battery heat loss, and saying they’re the same thing… They’re not.

    Overall this device would likely decrease range, spending heat to heat something that doesn’t need heating, and consumes a lot of power to do it.

    • vensonata

      So, how much energy does it take to heat your car for an hour at say -15 c? Are we talking 1 kwh or 5kwh?

      • Steve Grinwis

        Much closer to 5 kWh

        • sjc_1

          5 kWh to keep a car interior at 50f? The interior is less than 100 cubic feet.

          • Steve Grinwis

            You’re preaching to the choir. Since the surface is almost entirely single pane glass windows, it’s roughly as efficient as dumping heat directly outside, bypassing the cabin entirely.

            Up until now, we’ve always had waste heat with which to heat the cabin. Now that that’s not longer true, we should probably try to improve the thermal performance of the automobile envelope.

    • sault

      Good to know that we don’t see any real reduction until 0C and it’s not really a steep decline until -20C. At a discharge rate of 1000mAh, that’s around 0.33C for the 3000mAh cell being tested. This is the equivalent of driving a Chevy Bolt at 70mph down to empty. Of course, this uses 20kW average, meaning the battery itself is giving off 2 – 4kW of waste heat. 0.33C in the current LEAF would mean a constant 10kW of power consumption and 1 – 2 kW of waste heat to help heat the battery.

      If the EV is well-designed, this amount of waste heat could keep the battery above -20C in most places. The biggest obstacle is starting out with a cold battery before the car is even turned on, but a mindful EV driver would take care to ensure their car finishes charging right before the use it on cold days. So a nickel resistance heater is not really a good idea when the problem is mostly solved already with careful management.

      • Steve Grinwis


      • Roadside

        “mostly solved already with careful management”

        If it were as simple as that, we wouldn’t need companies/organizations like AAA or roadside assistance. 🙂

        • Steve Grinwis

          Careful management of the battery by the manufacturer, not careful management by the user. Very different things.

    • Dragon

      Well, your own chart is showing that capacity loss is negligible at 0C and pretty small at -5C. I think the real range loss doesn’t occur till you get towards -20C and a guy I was talking to in another comment thread said he really notices the range loss at that temperature in a Model S, estimating it at 30%. As to whether this new battery system would solve the problem, I don’t know. It does seem likely that it would do no good to quickly heat the battery with a thin layer of foil only to have the -20C coolant around the battery suck the heat back out. Seems likely it would be better to heat the coolant and save the weight of the little heater on each battery.

      You’re also ignoring regeneration benefits of heating the battery. At 32F and below, Model S prevents all regenerative braking and uses a constant 6kw or so heating the batteries (or, more likely, the coolant) till they warm enough to allow a decent amount of regeneration. Even then, a significant hill will overload the available regeneration and you’ll need to waste the energy with physical braking. If you live in flat land all this probably doesn’t matter much, but in terrain it makes a big difference.

      • Bob_Wallace

        ” it would do no good to quickly heat the battery with a thin layer of foil only to have the -20C coolant around the battery suck the heat back out”
        Heat the batteries directly. Don’t start circulating the coolant until the batteries are getting close to max ideal heat. Circulate slowly and gradually raise the coolant temp.

        Should be quicker than heating the coolant first.

        (That’s some guessing….)

        • Dragon

          Well, according to Wikipedia, a main property of coolant is that it has a high “heat capacity” meaning that it can absorb a lot of heat without raising much in temperature. So it seems to me that whether or not it’s circulating, it will absorb the heat generated by the foil around the batteries and remain relatively cold, keeping the batteries cold. Plain water is an example of something with high heat capacity and we all know how easy it is to get cold if you sit in cold water. Only after the batteries have generated enough heat to warm the coolant around them will they stay warm without adding much additional energy.

          I suspect the heat from the batteries will spread throughout the coolant reservoir whether or not it’s circulating, though maybe there is an insulated valve or something to limit the amount of coolant that comes in direct thermal contact with the cells in which case the foil wouldn’t have so much coolant to warm. I still doubt the foil would be more efficient than warming the coolant from some point source and letting the heat spread.

          I would guess that foil heaters on the cells would only make sense in a system where cells are well insulated (surrounded by something with low “thermal conductivity”), ie in an air-cooled system where the air is not circulating.

          • Bob_Wallace

            Is absorption the same thing as transmission? Is the coolant going to pull heat away from the cells rapidly or will there be a ‘heat bubble’ around the cells?

          • Dragon

            Absorption isn’t the same as transmission. We might assume transmission is low since you can have an undisturbed pool of water that’s significantly warmer near the surface than near the bottom and I assume coolant behaves in a similar way to water. Since heat in a pool of water will spread down many inches from the surface, I suspect the dimensions of the coolant tubes are small enough that any heat the batteries are generating will spread completely through the limited amount of coolant that comes near the batteries. This is especially true in a moving car where coolant should mix regardless of whether it is pumped.

   has detailed pics of the battery and coolant pipes that enter each module, but it’s not clear how large the coolant pipes/channels are inside the modules. It does seem fairly clear that the batteries aren’t literally surrounded by coolant but there must be a heat exchanging method that lets coolant pull heat away from batteries efficiently. There may be some info deeper in the thread but at over 51 pages I don’t really feel like trawling through…

          • Bob_Wallace

            OK, given that then I’m sticking with the idea that it’s quicker to heat at the individual cell level than to put the heater in the coolant reservoir and heat up all the coolant first.

            Heat the cells and don’t turn on the circulation pump until the cells are toasty. Circulate slowly at first so that the cold coolant doesn’t suck heat away from the cells faster than it can be replaced.

            In the coldest of cold conditions you might not want to circulate the coolant at all. Keep all the heat right at the cell level.

            Think of it like the thermostat in an ICE. The thermostat stays closed until the engine is hot, then opens to allow some coolant to circulate and keep the engine from overheating.

      • Steve Grinwis

        The Model S can’t recharge the battery below 0C? That’s terrible…

        My smart can do significant regen with the battery at -15C. Source: I was just driving around at -15C, and it was fine. The battery heater doesn’t even turn on till the car gets to around -25C, at which point it heats until the batter is -18C, and shuts off. This is to avoid the electrolyte freezing.

        It might not be full performance at -15C, but it’s there, and it’s significant.

        • Dragon

          From everything I’ve read, charging batteries below 0C damages them, which is why S prevents it and throws a bunch of power towards warming the batteries instead. I’m not sure how Smart EV would avoid that problem. Either the batteries are a different chemistry or you’re actually damaging them or the car is warming them for you. If you keep it in a warm garage or leave it on the charger it may be keeping them warm. S doesn’t warm its battery above 0C unless you turn on cabin heat or start the car.

          This says of Smart EV:

          “if the car isn’t connected to a power source, keep the temperature moderate. temperatures should stay between -4 F and 104 F. word to the wise: if you leave the car in temperatures under -13 F, the damage might be irreversible.”

          That would imply that the car does keep its battery above -13F as long as you have it plugged in, but it’s rather frightening that it could be damaged if you don’t have it plugged in! I’ve never seen such a warning on Model S and people on forums claim that even if unplugged it will use its own charge while parked to prevent the battery from getting cold (or hot) enough to cause damage.

          • Steve Grinwis

            I’m clearly not damaging them, as my battery tests show a 99.8% battery capacity after 2 years, including the aforementioned winter.

            It’s possible that the Smart is also warming the batteries during driving as well… That might actually make sense as I’ve noticed that below about -5C that the first few K seems to be more expensive than it should… So, perhaps it is warming things. It would be hard to tell the difference between: ‘The car isn’t charging because the battery is almost full’ and ‘The car isn’t charging because the battery is cold’. I don’t notice a difference in regenerating ability when cold though, I honestly don’t…

            -13F is -25C. That’s the temperature that the electrolyte will freeze, in the Smart or other batteries. The smart will use it’s internal power to keep the battery warm when it’s not plugged in. But this only works while the battery has charge. What they’re talking about is something more like this:

            “Don’t leave you car unplugged in the arctic for long periods of time, or the battery might freeze after the charge depletes”.

            I’ve clearly left my car unplugged for around 16 hours at -25C, and the only side effect I’ve noticed is about 5% charge depletion during that time as the battery warmer cycled.

            The issue, I think, is that Smarts tend to be second or summer cars. If you left your car unplugged for the duration of a Canadian winter, it would be easy to have it be damaged.

  • vensonata

    Interesting. They seem to be turning batteries from reptiles into mammals.

  • Marion Meads

    GReat, it consumes only 3.8% when heating from -4 deg F to 32 deg F in 20 seconds, and 5% from -22 deg F to 32 deg F in 30 seconds.

    Compare this to loss of capacity of 40%, and then you still have lowered efficiency of more than 10%.

    This is good for winter time, how about the Death Valley summer where typical days get 120 deg F, since this touted to be All Climate battery?

    • sault

      I was discussing this on another thread. Most EVs aside from the current LEAF have liquid cooled batteries. It basically pumps coolant to a radiator to dump heat into the ambient air. 120F is an extreme example of air temperature to dump heat into, but most of the country has adequate air temperature to keep the batteries cool in this way. Nissan developed the “lizard” battery to cope with the heat, but the main issue with high battery temps is their effect on battery lifespan and not acute / temporary range reduction like when cold weather hits.

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