Electric truck range is less in cold weather

[ What follows are excerpts from Calstart’s study of the effects cold weather had on lithium and Sodium Nickel Chloride e-truck batteries

Alice Friedemann   www.energyskeptic.com  author of “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts:  KunstlerCast 253, KunstlerCast278, Peak Prosperity]

CALSTART.  June 2013. E-truck performance in cold weather. Calstart.

Several different battery chemistries are used in transportation applications: Lead-Acid, Nickel Metal Hydride, Lithium-Ion, Sodium Nickel.  Table 1 shows the different e-trucks and their battery chemistry studied in this document.

cold battery e-truck maker battery type table1

SUMMARY OF DRIVING RANGE EXPECTATIONS

Figure 8 shows the combined impact of cold temperatures and cabin heating on an E-Truck equipped with a cabin heater with a power draw of 5 kW and an advertised range of 100 miles.

Figure 8: Impact of cold temperatures and cabin heating on the driving range of an E-Truck

Figure 8: Impact of cold temperatures and cabin heating on the driving range of an E-Truck

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

From the 80-mile maximum usable range, we can then see the impact of cold temperatures and cabin heating on driving range:

  • With ambient temperature throughout the day at 32°F (0°C), the E-Truck maximum usable range would decrease to 70 miles with no cabin heating and 50 miles with 4 hours of cabin heating at 5 kW power draw.
  • With ambient temperature throughout the day at 14°F (-10°C), the E-Truck maximum usable range would decrease to 60 miles with no cabin heating and 40 miles with four hours of cabin heating at 5 kW power draw.
  • With ambient temperature throughout the day at -4°F (-20°C), the E-Truck maximum usable range would decrease to 40 miles with no cabin heating and 20 miles with four hours of cabin heating at 5 kW power draw.

Lithium-Ion

Both high and low temperatures impact Lithium-Ion battery performance. At high temperatures, side reactions happen faster leading to faster battery degradation.

At cold temperatures, battery performance (power and energy) is lower due to poor ion transport. This leads to poor vehicle acceleration, limited capability to recover braking energy and lower driving range than experienced in warmer temperatures.

Each battery chemistry has its own unique performance degradation curve. Lithium-Ion batteries generally see their performance decrease gradually when ambient temperature drops from 80°F (27°C) to 32°F (0°C). However, performance falls off sharply when ambient temperature drops below 32°F (0°C).

  • At 32°F (0°C), relative capacity is about 90% of the capacity at the testing temperature of 77°F (25°C).
  • At 14°F (-10°C), relative capacity is about 80% of the capacity at the testing temperature of 77°F (25°C).
  • At -4°F (-20°C), relative capacity is about 60% of the capacity at the testing temperature of 77°F (25°C).

In addition, Lithium-Ion battery charging is much more challenging at cold temperatures as battery degradation is accelerated and the probability of a catastrophic failure is increased. As a result, Lithium-Ion batteries are generally inhibited from charging below 32°F (0°C).

cold battery lithium driving range figure 5

 

 

 

 

 

 

 

Figure 5: Impact of Lithium-Ion battery operating temperature on the driving range of an E-Truck with no cabin heating

When fleets deploy E-Trucks, they generally include a “buffer” to the advertised maximum range to limit “range anxiety”. This buffer is in addition to the OEM programmed battery buffer needed to preserve battery life. While every fleet may chose a different buffer, we chose a reasonable 20% that decreases the 100-mile advertised maximum range to an 80-mile maximum usable range with ambient temperature at 77°F (25°C). From this 80-mile maximum usable range, we can then see the impact of cold temperatures on driving range:

  • With ambient temperature throughout the day at 32°F (0°C), the E-Truck maximum usable range would decrease to 70 miles.
  • With ambient temperature throughout the day at 14°F (-10°C), the E-Truck maximum usable range would decrease to 60 miles.
  • With ambient temperature throughout the day at -4°F (-20°C), the E-Truck maximum usable range would decrease to 40 miles.

The 100-mile advertised maximum range to an 80-mile maximum usable range with ambient temperature at 77°F (25°C). From this 80-mile maximum usable range, we can then see the impact of cold temperatures on driving range:

  • With ambient temperature throughout the day at 32°F (0°C), the E-Truck maximum usable range would decrease to 70 miles.
  • With ambient temperature throughout the day at 14°F (-10°C), the E-Truck maximum usable range would decrease to 60 miles.
  • With ambient temperature throughout the day at -4°F (-20°C), the E-Truck maximum usable range would decrease to 40 miles.

Lithium-Ion battery performance is affected by cold temperatures. The extent of the performance degradation will depend on various factors:

  • Starting temperature (at which temperature are the batteries when the E- Truck starts its day),
  • Drive cycle (do the batteries have time to cool down when the vehicle is stopped on a delivery),
  • Outside temperature (what is the ambient temperature the batteries are exposed to).

We estimate that Lithium-Ion batteries used in current E-Trucks could lose 10 to 20% state of charge in typical Chicago winter weather (from 14°F to 32°F) and up to 40% in extreme cold weather (-4°F). For a 100-mile truck, this would represent a 10 to 20-mile reduction in driving range and up to a 40-mile reduction in extreme cold weather.

Sodium-Nickel batteries present the advantage of being able to operate at extreme temperatures from 40 to 149°F (-40 to +65°C) with no performance degradation. Since the electrolyte used in Sodium-Nickel batteries is solid and inactive at normal ambient temperatures, batteries are continuously kept at their internal working temperature of 518°F (270°C) in order to keep the electrolyte molten and the battery ready to use. Thus, Sodium-Nickel batteries provide consistent performance regardless of the outside temperature and charge normally at cold temperatures. In 2012, Motiv Power Systems was awarded a contract with a total value of $13.4 million from the City of Chicago to electrify up to 20 garbage trucks. In order to meet the range requirements provided by the City of Chicago (drive 60 miles all year-round), Motiv Power Systems uses Sodium-Nickel Chloride batteries. Figure 6 below shows the first US all- electric Class 8 refuse truck from Motiv Power Systems.

During initial testing in December 2013, no degradation of performance was observed. Between 50% and 60% of total battery capacity is used for driving regardless of the outside temperature, leaving enough battery capacity to run trash compaction and vehicle accessories.

Sodium-Nickel batteries present several drawbacks compared to Lithium-Ion batteries:

  • Sodium-Nickel batteries have lower power density than Lithium-Ion batteries. Thus, they are not suited for every truck application.
  • Sodium-Nickel batteries are not shipped at their operating temperature and thus need 24 hours to heat up to 280°C prior to being used.
  • Sodium-Nickel batteries are better for high usage applications (such as refuse), as the batteries will cool down if not in use or not connected to a power source. While this would not damage the batteries, a 24-hour period would be needed to reheat them to their 280°C operating temperature.
  • While connected to a power source, Sodium-Nickel batteries will draw power to keep batteries warm (less than 100 W).
  • There is currently only one commercial-stage supplier of Sodium-Nickel batteries for E-Truck applications (FIAMM), which is a limiting factor for the further adoption of Sodium-Nickel batteries.

We can see that cabin heating represents a significant energy draw on E-Truck batteries: from 16 kWh for a 4 kW cabin heater operated for four hours in a day, to 48 kWh for a 6 kW cabin heater operated for eight hours in a day. Chassis dynamometer testing of a Smith Electric Newton Step Van at the Argonne National Laboratory (see Chapter 7 for reference) showed a 40% increase in energy consumption (and thus a 40% decrease in driving range) at cold temperatures of 20°F (-7°C) compared to ambient temperatures of 70°F (-21°C).

cold battery figure 7 with cabin heating

 

 

 

 

 

 

 

Figure 7: Impact of cabin heating on the driving range of an E-Truck

From the 80-mile maximum usable range, we can then see the impact of cabin heating on driving range:

  • With 4 hours of cabin heating at 5 kW power draw, the E-Truck maximum usable range would decrease to 60 miles.
  • With 6 hours of cabin heating at 5 kW power draw, the E-Truck maximum usable range would decrease to 50 miles.
  • With 8 hours of cabin heating at 5 kW power draw, the E-Truck maximum usable range would decrease to 40 miles.

We can see that cabin heating represents a significant energy draw on E- Truck batteries: from 16 kWh for a 4 kW cabin heater operated for four hours in a day, to 48 kWh for a 6 kW cabin heater operated for eight hours in a day. Chassis dynamometer testing of a Smith Electric Newton Step Van at the Argonne National Laboratory showed a 40% increase in energy consumption (and thus a 40% decrease in driving range) at cold temperatures of 20°F (-7°C) compared to ambient temperatures of 70°F (-21°C). The

Figure 7 shows the impact of cabin heating on an E-Truck equipped with a cabin heater with a power draw of 5 kW and an advertised range of 100 miles.  Although outdoor temperatures would be low enough to require cabin heating, in order to quantify the impact of cabin heating on driving range, we assumed in that case cold temperatures would not affect battery performance.

We estimate that cabin heating use could decrease state of charge (SOC) by 20% in typical delivery operation and up to 40% in operation where the driver requires longer periods of cabin heating.

Lastly, we researched potential solutions that would help maintain E-Truck driving range in cold climate.

Table 3: List of potential solutions to help maintain E-Truck driving range in cold climate

cold battery table 3 part a solutions

 

 

 

cold battery table 3 part b solutions

 

Related articles

REFERENCES

  • The Truth About Electric Vehicles (EVs) in Cold Weather. On-Demand Webinar.
  • https://www.fleetcarma.com/Resources/the-truth-about-electric-vehicles-in- cold-weatherwebinar
  • American Automobile Association (2014). Extreme Temperatures Affect Electric Vehicle Driving Range, AAA Says. http://newsroom.aaa.com/2014/03/extreme- temperatures-affect-electricvehicle-driving-range-aaa-says/
  • Duoba, M., E. Rask, M. Meyer, APRF & Co (2012). Advanced Powertrain Research Facility AVTA Nissan Leaf testing and analysis. Argonne National Laboratory, October 12th, 2012. http://www.transportation.anl.gov/D3/data/2012_nissan_leaf/AVTALeaftestinga nalysis_Major %20summary101212.pdf
  • Pesaran A., Ph. D, S. Santhanagopalan, G. H. Kim, Addressing the Impact of Temperature Extremes on Large Format Li-Ion Batteries for Vehicle Applications. National Renewable Energy Laboratory, NREL/PR-5400-58145. 30th International Battery Seminar, Fort Lauderdale, FL, March 11-14, 2013. http://www.nrel.gov/docs/fy13osti/58145.pdf
  • Jehlik F., et al, Electric Heater Effects on two Medium Duty Electric Trucks, from Argonne & FedEx EV Evaluations. Handout for the National Governor’s Association Workshop on Advanced Vehicle Technologies and Infrastructure. Indianapolis, IN. May 19th, 2014.
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3 Responses to Electric truck range is less in cold weather

  1. Nathanael says:

    Durrr. We knew this from practical research by electric car manufacturers; the results are roughly the same, except slightly better for lithium-ion (only 67% of rated range, not 60%). Tesla decided to heat the batteries, which is correct. This is what electric bus manufacturers do now, and this is all the electric truck manufacturers of the future will do.

    • energyskeptic says:

      Yes, but that reduces the range! The energy provided by battery (cells) is cut in half within a battery pack because energy is lost every step of the way from cell to module to battery management system. Battery packs are made of modules with batteries constantly monitored by a battery management system that uses energy to keep track of each cell and cool them down. Elaborate control systems prevent a shorter battery life by making sure all cells have the same thermal history and protect against too fast charging or discharging. Each cell’s voltage, temperature, and internal resistance is monitored. The cooling system prevents thermal runaway or fatal destruction of cells at temperatures over 120 °F. Further energy is drained by air-conditioning, heating, lighting, dashboard displays, music, and GPS, all of them reducing the range.

      • Mark says:

        Alice,

        The temperature gauge in our older Mercedes Benz diesel (97-E300d) read 118F last weekend after about an hour in the sun, it was 105F outside. It didn’t take our IC engine too long to cool the interior of the car down 80F or so.

        Your post reminded me why we passed on changing out our ICE vehicle a couple of years ago. It will be interesting to see what AAA has to say about the 2nd and 3rd generation EV’s.

        “…The AAA tests revealed that while the average battery range for all three EVs was 105 miles at 75 degrees Fahrenheit, this dropped to 43 miles when the outside temperature was 20 degrees. AAA found that a warmer temperature has less effect on battery range, but still lowered it to an average of 69 miles on a full charge at 95 degrees Fahrenheit.”…

        http://editorial.autos.msn.com/blogs/post–aaa-ev-battery-range-but-by-more-than-half-in-cold-weather