A range extender is a fuel-based
auxiliary power unit (APU) that extends the range of a
battery electric vehicle
A battery electric vehicle (BEV), pure electric vehicle, only-electric vehicle, fully electric vehicle or all-electric vehicle is a type of electric vehicle (EV) that exclusively uses chemical energy stored in rechargeable battery packs, wi ...
by driving an
electric generator that charges the vehicle's battery. This arrangement is known as a
series hybrid
Hybrid vehicle drivetrains transmit power to the driving wheels for hybrid vehicles. A hybrid vehicle has multiple forms of motive power.
Hybrids come in many configurations. For example, a hybrid may receive its energy by burning gasoline, but sw ...
drivetrain. The most commonly used range extenders are
internal combustion engine
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal co ...
s, but
fuel-cells or other engine types can be used.
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
The California Air Resources Board (CARB or ARB) is the "clean air agency" of the government of California. Established in 1967 when then-governor Ronald Reagan signed the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Mot ...
(CARB).
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
A plug-in hybrid electric vehicle (PHEV) is a hybrid electric vehicle whose battery pack can be recharged by plugging a charging cable into an external electric power source, in addition to internally by its on-board internal combustion engi ...
(PHEV).
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.
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. 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.
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 , 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
Boston (), officially the City of Boston, is the capital city, state capital and List of municipalities in Massachusetts, most populous city of the Commonwealth (U.S. state), Commonwealth of Massachusetts, as well as the cultural and financ ...
(about ) 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 station
A filling station, also known as a gas station () or petrol station (), is a facility that sells fuel and engine lubricants for motor vehicles. The most common fuels sold in the 2010s were gasoline (or petrol) and diesel fuel.
Gaso ...
s, which provides them with a similar driving range to conventional automobiles.
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
Rotational frequency (also known as rotational speed or rate of rotation) of an object rotating around an axis is the frequency of rotation of the object. Its unit is revolution per minute (rpm), cycle per second (cps), etc.
The symbol fo ...
. These design features allow an REEV to convert fossil fuel energy to electric power and vehicle motion relatively efficiently.
Generations
*The first generation range extenders are off the shelf
internal combustion engine
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal co ...
s.
*The second generation consists of piston engines with new designs from scratch for fairly constant load in series hybrids. They include the
wankel engines,
rotary combustion engine
A pistonless rotary engine is an internal combustion engine that does not use pistons in the way a reciprocating engine does. Designs vary widely but typically involve one or more rotors, sometimes called rotary pistons. Although many different ...
s and
free piston engines.
*The third generation are
micro turbines and
fuel cell
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen fuel, hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most bat ...
s that work at constant load.
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:
* The vehicle must have a rated
all-electric range of at least . This is higher than the required of a
zero-emission vehicle;
* The
auxiliary power unit (APU) must provide range less than or equal to 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
Super ultra-low emissions vehicle (SULEV) is a U.S. classification for passenger vehicle emissions. The classification is based on producing 90% fewer emissions than the average gasoline-powered vehicle. The SULEV standard is stricter than the stan ...
(SULEV) requirements; and
* The APU and all associated fuel systems must comply with zero
evaporative emissions requirements.
Applications
Range extenders are commonly used in
marine (
autonomous underwater vehicle),
aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. ...
and Generator/Utility,
automotive and
hybrid electric vehicle
A hybrid electric vehicle (HEV) is a type of hybrid vehicle that combines a conventional internal combustion engine (ICE) system with an electric propulsion system (hybrid vehicle drivetrain). The presence of the electric powertrain is intended ...
applications.
Automotive
Chevrolet Volt
General Motors describes the
Chevrolet Volt as an
electric vehicle
An electric vehicle (EV) is a vehicle that uses one or more electric motors for propulsion. It can be powered by a collector system, with electricity from extravehicular sources, or it can be powered autonomously by a battery (sometimes c ...
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.
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 in charge-depleting
Charge-depleting or EV mode refers to a mode of vehicle operation that is dependent on the
energy from the battery pack. Battery electric vehicles operate solely in this mode. Most plug-in hybrids operate in charge-depleting mode at startup, and ...
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.
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 . GM also reported that Volt owners driving is more than 63% in all-electric mode. Volt owners who charge regularly typically drive more than between fill-ups and visit the gasoline station less than once a month. A similar report, issued by GM in August 2016, reported that Volt owners have accumulated almost driven in EV mode, representing 60% of their total distance traveled.
BMW i3
The BMW i3 all-electric car with at least 22 kWh battery capacity offers an optional gasoline-powered range extender APU. The range extender is the same 647 cc two-cylinder gasoline engine used in the BMW C650 GT scooter with a fuel tank. The US model originally had its tank electronically limited to a smaller 7 L capacity. The range extender engages when the battery level drops to 6%. It generates electricity to extend the range from to 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.
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.
The range-extender option costs an additional in the United States, an additional (~ ) in France, and (~ ) in the Netherlands.
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.
Other examples
Other range-extended electric vehicles include the discontinued Cadillac ELR and the discontinued Fisker Karma
The Fisker Karma is a luxury vehicle, luxury plug-in Range extender (vehicle), range-extended electric sports sedan produced by Fisker Automotive in 2012. The cars were manufactured at Valmet Automotive in Finland.
The United States Environm ...
. 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
Concepts are defined as abstract ideas. They are understood to be the fundamental building blocks of the concept behind principles, thoughts and beliefs.
They play an important role in all aspects of cognition. As such, concepts are studied by s ...
crossover showcased at the 2015 Frankfurt Auto Show
The International Motor Show Germany or International Mobility Show Germany, in German known as the ''Internationale Automobil-Ausstellung'' (''IAA'' – International Automobile Exhibition), is one of the world's largest mobility shows. It cons ...
. The technology, without the plug-in ability, had been deployed to the Nissan Note e-Power and Nissan Kicks e-Power.
The LEVC TX
The LEVC TX (previously known as the TX5) is a purpose-built hackney carriage manufactured by the British commercial vehicle maker London EV Company (LEVC), a subsidiary of the Chinese auto-maker Geely. It is the latest in a succession of purpo ...
London taxi was launched in 2017 and features a 33 kWh battery that is charged by a 1.5-litre gasoline engine.
The Lixiang One is a large SUV which combines a 41-kWh battery with a small 1.2-litre gasoline engine.
This approach has also been used for heavy vehicles, such as Wrightbus's Gemini 2
Gemini 2 (Gemini-Titan 2; GT-2) was the second spaceflight of the American human spaceflight program Project Gemini, and was launched and recovered on January 19, 1965. Gemini 2, like Gemini 1, was an uncrewed mission intended as a test flig ...
and New Routemaster
The New Routemaster, originally referred to as the New Bus for London and colloquially as the Borismaster or Boris Bus, is a low-floor diesel double-decker bus operated in London, England. Designed by Heatherwick Studio and manufactured by Wri ...
buses.
Ford has patents for a bed mounted gasoline-powered generator for their fully electric pickups. Rivian has patents for bed mounted additional batteries for increased range. Rivian electric trucks can charge each other for extended range.
Unmanned aerial vehicles
The 2010 Wolverine 3 program included an ICE range extender for its unmanned aerial vehicle
An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controlle ...
.
Powertrain
A range-extended electric vehicle uses a series hybrid
Hybrid vehicle drivetrains transmit power to the driving wheels for hybrid vehicles. A hybrid vehicle has multiple forms of motive power.
Hybrids come in many configurations. For example, a hybrid may receive its energy by burning gasoline, but sw ...
drivetrain.
See also
* Genset trailer
A genset trailer is a range extending device for use with battery electric vehicles consisting of an internal combustion engine and an electric generator (collectively called a genset). They run on traditional fuels such as gasoline or diesel an ...
* Hybrid vehicle drivetrain
Hybrid vehicle drivetrains transmit power to the driving wheels for hybrid vehicles. A hybrid vehicle has multiple forms of motive power.
Hybrids come in many configurations. For example, a hybrid may receive its energy by burning gasoline, but sw ...
* Microturbines
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...
* List of hybrid and plug-in hybrid vehicles
References
{{Reflist, 30em
Vehicle technology
Electric vehicles
Plug-in hybrid vehicles