Range extender (vehicle)
Range extender is an auxiliary power unit built-in or externally attached to a all-electric (BEV) or plug-in hybrid electric vehicle (PHEV) to increase its all-electric range (AER). The most commonly used range extenders are internal combustion engines that drive an electric generator which in turn supplies the battery and electric motor with electricity. The range extender can also be powered by a fuel-cell or other energy sources. The 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 concerns. Plug-in hybrids with a built-in range extender unit, such as the Chevrolet Volt, are also known as extended-range electric vehicles (EREV); and electric cars with a range-extender unit, such as the BMW i3 with such unit, are called range-extended battery-electric vehicle (BEVx) by the California Air Resources Board.
- The first generation range extenders are off the shelf internal combustion engines.
- The second generation consists of piston engines with new designs from scratch for fairly constant load in series hybrids. They include the wankel engines and rotary combustion engines and free piston engines.
- The third generation are the micro turbines and fuel cells that work at constant load.
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:
- The vehicle must have a rated all-electric range of at least 75 mi (121 km). This is higher than the 50 mi (80 km) required of a zero-emission vehicle;
- The auxiliary power unit (APU) must provide range less than, or at most equal to, that battery range;
- The APU must not be capable of switching on until the battery charge has been depleted;
- The vehicle must meet super ultra low emission vehicle (SULEV) requirements; and
- The APU and all associated fuel systems must comply with zero evaporative emissions requirements.
ICE range extender
The technology for the ICE range extender is commonly used in marine (autonomous underwater vehicle), aircraft and Generator/Utility, automotive and hybrid electric vehicle range extender applications.
Unmanned aerial vehicles
General Motors describes the Chevrolet Volt as an electric vehicle equipped with 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. 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." The Volt operates as a purely electric car for the first 25 to 50 miles (40 to 80 km) in charge-depleting mode. When the battery capacity drops below a pre-established threshold from full charge, the vehicles 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.
According to General Motors' real time tally of miles driven by Volt owners in North America, by mid June 2014 they have accumulated more than 500 million all-electric miles (805 million km). GM also reported that Volt owners are doing more than 63% of their overall driving in all-electric mode, and among Volt owners who charge regularly, they typically drive more than 970 mi (1,560 km) between fill-ups and visit the gasoline station less than once a month.
BMW i offers the BMW i3 all-electric car with an optional gasoline-powered range extender engine added. The range extender is powered by the same 647 cc two-cylinder gasoline engine used in the BMW C650 GT motorcycle with a 9 L (2.0 imp gal; 2.4 US gal) fuel tank. The range extender engine only engages when the battery level drops to a pre-specified point, acting purely as a generator to produce electricity to extend the range from 130 to 160 km (80 to 100 mi) to 240 to 300 km (150 to 190 mi) The i3 performance in range-extending mode may be more limited than when it is running on battery power, as BMW clarified that the range extender is designed not for long-distance travel but purely as an emergency backup to keep the electric system going until the next recharging location.
The range-extender option of the BMW i3 was designed to meet the California Air Resources Board (CARB) regulation for an auxiliary power unit (APU) called REx. According to rules adopted in March 2012 by CARB, 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 30% after the pack has been depleted in normal use, is strictly limited in the additional range it can provide.
Parallel hybrid and series-parallel hybrid
Parallel hybrids and series-parallel hybrids operate most of the time in blended mode while charge-depleting. Because the Toyota Prius Plug-in Hybrid operates as a series-parallel hybrid, the U.S. EPA estimated its all-electric range for blended operation on a combination of electricity (from a fully charged battery pack) and gasoline as 11 mi (18 km) until the battery is depleted. Other plug-in hybrids that operated mostly in blended mode are the Ford C-Max Energi, Ford Fusion Energi and Honda Accord Plug-in Hybrid.
On the other hand, series hybrids are also been referred to as extended-range electric vehicles (EREV) or range-extended electric vehicles (REEV), in case they are designed to be run mostly by the battery, but have a gasoline or diesel generator to recharge the battery when going on long trips. The Chevrolet Volt, Fisker Karma and the upcoming Cadillac ELR are series plug-in hybrids.
- Electric vehicles with range extender as a suitable technology
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- Range Extenders for Electric Vehicles Land, Water & Air 2012-2022
- Electric vehicle and range extender
- The ideal range extender
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