A prototype AC Propulsion tzero electric car with an external range-extender or genset trailer, 1999

A range extender is a fuel-based auxiliary power unit (APU) that extends the range of a battery electric vehicle by driving an electric generator that charges the vehicle's battery. This arrangement is known as a series hybrid drivetrain. The most commonly used range extenders are internal combustion engines, but fuel-cells or other engine types can be used.[1]

Range extender vehicles are also referred to as extended-range electric vehicles (EREV), range-extended electric vehicles (REEV), and range-extended battery-electric vehicle (BEVx) by the California Air Resources Board (CARB).[2]

Many range extender vehicles, including the Chevrolet Volt and the BMW i3, are able to charge their batteries from the grid as well as from the range extender, and therefore are a type of plug-in hybrid electric vehicle (PHEV).[3][4]

Motivation

The key function of the range extender is to increase the vehicle's range. Range autonomy is one of the main barriers for the commercial success of electric vehicles, and extending the vehicle's range when the battery is depleted helps alleviate range anxiety.[5]

A range extending vehicle design can also reduce the consumption of the range extending fuel (such as gasoline) by using the primary fuel (such as battery power), while still maintaining the driving range of a single fuel vehicle powered by a range extending fuel such as gasoline. The range extending fuel is generally considered to be less environmentally and economically friendly to use than the primary fuel source, so the vehicle control system gives preference to using the primary fuel if it's available. However, due to range limitations with the primary fuel source, the range extending fuel allows the vehicle to get many of the cost and environmental benefits of the primary fuel, while maintaining the full driving range of the range extending fuel source.[6] That said, the benefits (cost, carbon emissions) derived from using a vehicle with a range extender ultimately depend on how the vehicle is driven, and in particular how often the range extender is used.[7]

As an example, cars such as the Chevrolet Volt and the BMW i3 with optional range extender are equipped with sufficiently large batteries to drive 80–160 km (50–100 miles), which is enough for many trips but not sufficient to drive long distances. As such, the driver may use battery power for commuting and daily driving, but still be able to drive from New York to Boston (about 320 km, 200 miles) by using the auxiliary gasoline internal combustion engine, without stopping frequently to charge the battery (which can take hours). The vehicle owner therefore accrues the benefits of using cheaper and less carbon-intensive electric power for most driving, while maintaining the ability to embark on longer trips with the same vehicle.

When a range extender uses conventional fuels they can re-fuel at regular fuel stations, which provides them with a similar driving range to conventional automobiles.[8][9][10]

As an REEV is only propelled by the electric motor it can do away with the weight and cost associated with the gearbox transmission system typically used in internal combustion engine cars. Further, as the range extender does not need to increase or decrease output in line with the power needs of the vehicle (this task is handled by the electric motor) the range extender can be sized to satisfy the vehicle's average power requirement rather than its peak power requirement (such as when accelerating). The range extender can also operate much closer to its most efficient rotational speed. These design features allow an REEV to convert fossil fuel energy to electric power and vehicle motion relatively efficiently.

Generations

CARB regulation

According to 2012 Amendments to the Zero Emission Vehicle Regulations adopted in March 2012 by the California Air Resources Board (CARB), a range-extended battery-electric vehicle, designated as BEVx, should comply, among others, with the following criteria:[2]

Applications

Range extenders are commonly used in marine (autonomous underwater vehicle), aircraft and Generator/Utility, automotive[12] and hybrid electric vehicle applications.[13]

Automotive

Chevrolet Volt

The Chevrolet Volt is a series plug-in hybrid referred by General Motors as "an electric car with extended range."

General Motors describes the Chevrolet Volt as an electric vehicle equipped with a 16 kWh battery plus a "range extending" gasoline powered internal combustion engine (ICE) as a genset and therefore dubbed the Volt an "Extended Range Electric Vehicle" or E-REV.[3][4][14] In a January 2011 interview, the Chevy Volt's Global Chief Engineer, Pamela Fletcher, referred to the Volt as "an electric car with extended range."[15] The Volt operates as a purely electric car for the first 40–80 km (25–50 miles) in charge-depleting mode. When the battery capacity drops below a pre-established threshold from full charge, the vehicle enters charge-sustaining mode, and the Volt's control system will select the most optimally efficient drive mode to improve performance and boost high-speed efficiency.[3][16][17]

According to General Motors' real time tally of the distance driven by Volt owners in North America, by mid June 2014 they had accumulated more than 800 million all-electric km (500 million miles). GM also reported that Volt owners driving is more than 63% in all-electric mode. Volt owners who charge regularly typically drive more than 1,560 km (970 miles) between fill-ups and visit the gasoline station less than once a month.[18] A similar report, issued by GM in August 2016, reported that Volt owners have accumulated almost 2.4 billion km (1.5 billion miles) driven in EV mode, representing 60% of their total distance traveled.[19]

BMW i3

An optional range-extender is available for the BMW i3, which allows the car to qualify as a range-extended battery-electric vehicle (BEVx) according to the California Air Resources Board regulations.

The BMW i3 all-electric car with at least 22 kWh battery capacity offers an optional gasoline-powered range extender APU.[20] The range extender is the same 647 cc two-cylinder gasoline engine used in the BMW C650 GT scooter with a 9 L (2.0 imp gal; 2.4 US gal) fuel tank. The US model originally had its tank electronically limited to a smaller 7 L capacity.[21] The range extender engages when the battery level drops to 6%. It generates electricity to extend the range from 130–160 km (80–100 miles) to 240–300 km (150–190 miles)[22][23] Performance in range-extending mode may be more limited than when it is running on battery power, as BMW designed the range extender as a backup to enable reaching a recharging location.[24]

According to BMW, at the beginning of the i3 release, the use of range-extender was much more than the carmaker expected, more than 60%. Over time it has decreased significantly, with some people almost never using it, and by 2016 it is being regularly used in fewer than 5% of i3s.[25]

The range-extender option costs an additional US$3,850 in the United States,[26] an additional €4,710 (~ US$6,300) in France,[27] and €4,490 (~ US$6,000) in the Netherlands.[28]

The range-extender option of the BMW i3 was designed to meet the CARB regulation for an auxiliary power unit (APU) called REx. According to rules CARB adopted in March 2012, the 2014 BMW i3 with a REx unit fitted will be the first car to qualify as a range-extended battery-electric vehicle or "BEVx." CARB describes this type of electric vehicle as "a relatively high-electric range battery-electric vehicle (BEV) to which an APU is added." The APU, which maintains battery charge at about 6% after the pack has been depleted in normal use, is strictly limited in the additional range it can provide.[2][29]

Other examples

The discontinued Fisker Karma was an extended-range electric vehicle.

Other range-extended electric vehicles include the discontinued Cadillac ELR and the discontinued Fisker Karma.[30][31][32] In June 2016, Nissan announced it will introduce a compact range extender car in Japan before March 2017. The series plug-in hybrid will use a new hybrid system, dubbed e-Power, which debuted with the Nissan Gripz concept crossover showcased at the 2015 Frankfurt Auto Show.[33] The technology, without the plug-in ability, had been deployed to the Nissan Note e-Power and Nissan Kicks e-Power.

The LEVC TX London taxi was launched in 2017 and features a 33 kWh battery that is charged by a 1.5-litre gasoline engine.[34]

The Lixiang One is a large SUV which combines a 41-kWh battery with a small 1.2-litre gasoline engine.[35][36]

This approach has also been used for heavy vehicles, such as Wrightbus's Gemini 2[37] and New Routemaster[38] buses.

Hydrogen fuel cells have also been used as a range extender for battery electric buses, allowing them to have greater range.[39] For example, the Mercedes-Benz eCitaro has a range of 280 kilometres (170 mi) as a battery electric model, with the eCitaro fuel cell bus having a range of 400 kilometres (250 mi) thanks to a 60kW Toyota fuel cell that recharges the battery.[40]

Ford has patents for a bed mounted gasoline-powered generator for their fully electric pickups.[41] Rivian has patents for bed mounted additional batteries for increased range.[42] Rivian electric trucks can charge each other for extended range.[43]

Unmanned aerial vehicles

The 2010 Wolverine 3 program included an ICE range extender for its unmanned aerial vehicle.[44]

Powertrain

Schematic classification of alternative powertrains

A range-extended electric vehicle uses a series hybrid drivetrain.

See also

References

  1. ↑ Harrop, Peter (2015-03-13). "Hybrid vehicle range extenders: goodbye pistons". IDTechEx. Retrieved 2015-05-18.
  2. 1 2 3 John Voelcker (2013-10-23). "2014 BMW i3 Electric Car: Why California Set Range Requirements, Engine Limits". Green Car Reports. Retrieved 2014-01-19.
  3. 1 2 3 Matthe, Roland; Eberle, Ulrich (2014-01-01). "The Voltec System – Energy Storage and Electric Propulsion". Retrieved 2014-05-04.
  4. 1 2 "Chevrolet Volt Hits Road, Ahead of Schedule". The New York Times. 2009-06-25. Retrieved 2014-01-19.
  5. ↑ Vortisch, Peter; Chlond, Bastian; Weiß, Christine; Mallig, Nicolai (June 2015). "Electric Vehicles with Range Extender as a Suitable Technology (EVREST)". Karlsruher Institut für Technologie. Retrieved 2015-05-18.
  6. ↑ Bradley, Thomas; Frank, Andrew. "Design, demonstrations and sustainability impact assessments for plug-in hybrid electric vehicles" (PDF).
  7. ↑ Bradley, Thomas; Quinn, Casey. "Analysis of plug-in hybrid electric vehicle utility factors" (PDF).
  8. ↑ Michael Graham Richard (2009-10-14). "Could Range Anxiety Sabotage the Promise of Electric Cars?". Discovery's Planet Green. Archived from the original on 2013-12-03. Retrieved 2010-03-14.
  9. ↑ "Plug-In Hybrid Electric Vehicle (PHEV)". Center for Energy and the Global Environment, Virginia Tech. Archived from the original on 2011-07-20. Retrieved 2010-12-29.
  10. ↑ "What Is A Plug-in Hybrid Car?". HybridCars.com. Retrieved 2010-12-29.
  11. ↑ Range Extenders for Electric Vehicles Land, Water & Air 2013-2023. 2013-07-08 – via www.idtechex.com.
  12. ↑ "Electric vehicle and range extender" (PDF).
  13. ↑ "Multiple Use Engine Including marine, military, automobile, light aircraft". www.dukeengines.com.
  14. ↑ Jonathan Oosting (2010-10-12). "Is the Chevrolet Volt a true electric car? General Motors defends EV label". MLive.com. Retrieved 2010-06-02.
  15. ↑ Kuchment, Anna (January 2011). "Practically Green: A Q&A with the Chevy Volt's Chief Engineer". Scientific American. Vol. 304, no. 1. Nature America. p. 25. ISSN 0036-8733. Retrieved 2011-03-27.
  16. ↑ Norman Mayersohn (2010-10-15). "Sorting Myth From Fact as Volt Makes Its Debut". New York Times. Retrieved 2010-10-17.
  17. ↑ Frank Markus (2010-10-10). "Unbolting the Chevy Volt to See How it Ticks". Motor Trend. Retrieved 2010-10-11.
  18. ↑ "Chevrolet Volt Owners Surpass Half a Billion Electric Miles" (Press release). US: General Motors. 2014-06-17. Retrieved 2014-07-02.
  19. ↑ Cobb, Jeff (2016-08-01). "100,000th Chevy Volt Sold in US". HybridCars.com. Retrieved 2016-08-09.
  20. ↑ Viknesh Vijayenthiran (2010-07-20). "First Major Outing For BMW Megacity Vehicle At 2012 London Olympic Games". Motor Authority. Retrieved 2010-07-23.
  21. ↑ John O'Dell. "BMW i3 Range Boost: Up 40% for 2017". The Green Car Guy. Retrieved 2020-09-18.
  22. ↑ Jay Cole (2013-07-29). "BMW i3 Range Extender To Offer Up to 87 More Miles, Decreases Performance". InsideEVs. Retrieved 2013-07-29.
  23. ↑ Greg Kable (2013-02-24). "First rides in BMW i8 hybrid sportscar and all-electric i3". Autocar. Retrieved 2013-02-27.
  24. ↑ John Voelcker (2013-03-12). "BMW i3 Electric Car: ReX Range Extender Not For Daily Use?". Green Car Reports. Retrieved 2013-03-12.
  25. ↑ Duff, Mike (2016-03-08). "BMW i Chief: Larger i Models Will Offer Optional Range-Extender". Car and Driver. Retrieved 2016-03-18.
  26. ↑ Benjamin Preston (2013-07-29). "BMW Unveils i3 Electric Car". The New York Times. Retrieved 2013-07-29.
  27. ↑ Michaël Torregrossa (2013-07-30). "Voiture électrique – La BMW i3 officiellement révélée" [Electric car – the BMW i3 officially revealed] (in French). Association pour l'Avenir du Véhicule Electrique Méditerranéen (AVEM). Retrieved 2013-07-31.
  28. ↑ Eric Loveday (2013-07-22). "Official: BMW i3 Range Extender Option Adds 4,490 Euros ($5,919 US) to Price Tag in Netherlands". InsideEVs.com. Retrieved 2013-07-29.
  29. ↑ Tom Moloughney (2014-10-24). "The i3 REx: One Owners Thoughts on the BEVx Restrictions". BMWBlog. Retrieved 2014-01-24.
  30. ↑ Eric Loveday (2013-02-06). "Frost & Sullivan Predicts Boom in Extended-Range Electric Vehicles". PluginCars.com. Retrieved 2013-08-11.
  31. ↑ Sam Abuelsamid (2009-04-02). "What is a series hybrid/extended range electric vehicle?". Autoblog Green. Retrieved 2013-08-11.
  32. ↑ John Voelcker (2012-03-13). "2012 Fisker Karma -Review". Green Car Reports. Retrieved 2013-08-11.
  33. ↑ Greimel, Hans (2016-06-25). "Nissan's to-do list: Range, autonomy". Automotive News. Retrieved 2016-06-27.
  34. ↑ Moldrich, Curtis (2018-04-04). "LEVC TX review: London's new electric taxi driven". Car Magazine. UK. Retrieved 2018-10-17.
  35. ↑ "Li Xiang Launches With "One" SUV With Six Seats, Four Screens, Hybrid Powertrain". Carscoops. 2019-03-21.
  36. ↑ "理想汽车 | 创造移动的家, 创造幸福的家" [Ideal car | create a mobile home, create a happy home]. lixiang (in Chinese). China. Retrieved 2021-10-06.
  37. ↑ Navarro, Xavier (2009-05-14). "A hybrid bus that cuts fuel consumption in half". Autoblog. Retrieved 2015-11-21.
  38. ↑ "New Routemaster technical specifications" (PDF). Wrights Group. Retrieved 2015-11-21.
  39. ↑ "Hamburg to test the eCitaro with fuel cell range extender in 2021". Sustainable Bus. 2019-09-05. Retrieved 2022-10-27.
  40. ↑ "Drum roll for Mercedes eCitaro with FC range extender". electrive.com. 23 May 2023. Retrieved 2023-08-10.
  41. ↑ "Ford F-150 Electric Patent Shows Range-Extending Gas Generator". Motor1.com. Retrieved 2021-10-24.
  42. ↑ Stumpf, Rob (11 November 2020). "Rivian Patents Removable Bed-Mounted Battery Pack for Extended Range". The Drive. Retrieved 2021-10-24.
  43. ↑ "Rivian's electric trucks can charge each other". Engadget. Retrieved 2021-10-24.
  44. ↑ Brooke, Lindsay (2010-06-21). "Secrets of Ricardo's new UAV engine may spawn range-extender for EVs". Society of Automotive Engineers International. Retrieved 2015-11-22.
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