{{Short description|Systems vehicles with multiple power sources use to transmit power to the wheels}} '''Hybrid vehicle drivetrains''' transmit power to the driving wheels for [[hybrid vehicle]]s. A hybrid vehicle has multiple forms of motive power, and can come in many configurations. For example, a hybrid may receive its energy by burning gasoline, but switch between an [[electric motor]] and a [[Internal combustion engine|combustion engine]].
A typical [[powertrain]] includes all of the components used to transform stored [[potential energy]]. Powertrains may either use chemical, solar, nuclear or kinetic energy for propulsion. The oldest example is the steam locomotive. Modern examples include [[electric bicycle]]s and [[hybrid electric vehicle]]s, which generally combine a [[Electric-vehicle battery|battery]] (or [[supercapacitor]]) supplemented by an [[internal combustion engine]] (ICE) that can either recharge the batteries or power the vehicle. Other hybrid powertrains can use [[flywheel]]s to store energy.
Among different types of hybrid vehicles, only the electric/ICE type is commercially available as of 2017. One variety operated [[in parallel]] to provide power from both motors simultaneously. Another operated [[in series]] with one source exclusively providing the power and the second providing electricity. Either source may provide the primary motive force, with the other augmenting the primary.
Other combinations offer efficiency gains from superior energy management and regeneration that are offset by cost, complexity and battery limitations. Combustion-electric (CE) hybrids have battery packs with far larger capacity than a combustion-only vehicle. A combustion-electric hybrid has batteries that are light that offer higher energy density and are far more costly. ICEs require only a battery large enough to operate the electrical system and ignite the engine.<ref>{{cite web |url=http://www.greencarcongress.com/2009/03/doe-to-award-up-to-24b-for-advanced-batteries-electric-drive-components-and-electric-drive-vehicle-d.html#more |title=DOE to Award Up to $2.4B for Advanced Batteries, Electric Drive Components, and Electric Drive Vehicle Demonstration/Deployment Projects |publisher=Green Car Congress |date=March 19, 2009}}</ref> {{toclimit|3}}
== History == Electrical vehicles have a long history combining internal combustion and electrical transmission{{snd}} as in a [[diesel–electric transmission|diesel–electric]] power-train{{snd}} although they have mostly been used for rail [[locomotive]]s. A diesel–electric powertrain fails the strict definition of hybrid because the electric drive transmission directly replaces the mechanical transmission rather than being a supplementary source of motive power.
One of the earliest forms of hybrid land vehicle was the 'trackless' [[trolleybus]] experiment in The United States (New Jersey) that ran from 1935 to 1948, which normally used traction current delivered by wire. The trolleybus was fitted with an [[internal combustion engine]] to power the mechanical drivetrain directly, not to generate electricity for the traction motor. This enabled the vehicle to be used for revenue service where there was no contact wire.
Since the 1990s trolleybus hybrids have been introduced with small power plants to provide a low speed capability for emergency and maintenance but not to support general revenue service.
==Types by design==
=== Parallel hybrid === <!-- Other articles link here. --> [[File:Hybridpar.svg|thumb|Structure of a parallel hybrid electric vehicle. The grey squares represent [[differential gear]]s.]] Parallel hybrid systems have both an internal combustion engine and an electric motor that can both individually drive the car or both coupled up jointly giving drive. This is the most common hybrid system as of 2016.
If they are joined at an axis (in parallel)'','' the speeds at this axis must be identical and the supplied [[torques]] will add together (most electric bicycles are of this type). When only one of the two sources is in use, the other must be connected via a one-way [[clutch]] or [[freewheel]] so it can rotate freely.
With cars the two sources may be applied to the same shaft (for example with the electric motor connected between the engine and transmission), turning at equal speeds and the torques adding up with the electric motor adding or subtracting torque to the system as necessary. (The first two generations of [[Honda Insight]] use this system.)
[[Parallel Hybrid|Parallel hybrids]] can be further categorized by the balance between the different motors are at providing motive power: the ICE may be dominant (engaging the electric motor only in specific circumstances) or vice versa; while in others can run on the electric system alone but because current parallel hybrids are unable to provide electric-only or internal combustion-only modes they are often categorized as '''mild hybrids''' (see below).
Parallel hybrids rely more on [[regenerative braking]] and the ICE can also act as a generator for supplemental recharging. This makes them more efficient in urban 'stop-and-go' conditions. They use a smaller battery pack than other hybrids. [[Honda]]'s early Insight, [[Honda Civic Hybrid|Civic]], and [[Honda Accord Hybrid|Accord]] hybrids using [[Integrated Motor Assist|IMA]] are examples of production parallel hybrids.<ref name="UCSHbrid">{{cite web|url=http://www.hybridcenter.org/hybrid-center-how-hybrid-cars-work-under-the-hood-2.html |title=Hybrids Under the Hood (Part 2): Drivetrains |publisher=Hybrid Center ([[Union of Concerned Scientists]]) |url-status=dead |access-date=2010-03-18 |archive-url=https://web.archive.org/web/20100111032823/http://www.hybridcenter.org/hybrid-center-how-hybrid-cars-work-under-the-hood-2.html |archive-date=2010-01-11 }}</ref> General Motors [[Parallel Hybrid Truck]] (PHT) and [[BAS Hybrid]]s such as the [[Saturn Vue]] and [[Saturn Aura|Aura]] Greenline and [[Chevrolet Malibu]] hybrids also employ a parallel hybrid architecture.
====Through the Road (TTR) hybrid==== An alternative parallel hybrid is the "through the road" type.<ref>{{cite web |title=What do you mean when you say Through-The-Road-Hybrid (TTRH)? |publisher=Protean Electric |url=http://www.proteanelectric.com/en/faqs/what-do-you-mean-when-you-say-through-the-road-hybrid-ttrh/ |access-date=July 15, 2014 |archive-date=September 24, 2015 |archive-url=https://web.archive.org/web/20150924082500/http://www.proteanelectric.com/en/faqs/what-do-you-mean-when-you-say-through-the-road-hybrid-ttrh/ |url-status=dead }}</ref><ref>{{cite web |title=Through-The-Road (TTR) Hybrid - Through-The-Roof Potential - 598 |publisher=Argonne National Laboratory |url=http://www.transportation.anl.gov/pdfs/HV/598.PDF |access-date= July 15, 2014}}</ref> In this system a conventional drivetrain powers one axle, with an electric motor or motors driving another. This arrangement was used by the earliest 'off track' trolleybuses. It in effect provides a complete backup power train. In modern motors batteries can be recharged through regenerative braking or by loading the electrically driven wheels during cruise. This allows a simpler approach to power-management. This layout also has the advantage of providing four-wheel-drive in some conditions. (An example of this principle is a bicycle fitted with a front hub motor, which assists the cyclist's pedal power at the rear wheel.) Vehicles of this type include the [[Audi hybrid vehicles#Audi 100 Duo II|Audi 100 Duo II]] and [[Subaru VIZIV]] concept cars, [[Peugeot 3008#Hybrid version|Peugeot 3008]], [[Peugeot 508]], [[Peugeot 508#508 RXH|508 RXH]], [[Citroën DS5]] (all using [[Groupe PSA|PSA]]'s [[PSA HYbrid4|HYbrid4]] system), the [[Volvo V60#V60 Plug-in Hybrid|Volvo V60 plug-in hybrid]], the [[BMW 2 Series Active Tourer]], [[BMW i8]] and the [[Honda NSX (second generation)|second generation Honda NSX]].
=== Series hybrid === <!-- Other articles link here. --> [[File:Hybridpeak.svg|thumb|Structure of a series-hybrid vehicle. The grey square represents a differential gear. An alternative arrangement (not shown) is to have electric motors at two or four wheels.]] Series hybrids are also referred to as [[Range extender (vehicle)|extended-range electric vehicles]] (EREV)<ref Name=R1>{{cite web |title=The Voltec System - Energy Storage and Electric Propulsion |url=https://www.researchgate.net/publication/262004450 |last1=Matthe |first1=Roland |last2=Eberle| first2=Ulrich |date=2014-01-01 |access-date=2014-05-04}}</ref> or range-extended electric vehicles (REEV), or electric vehicle with extended range (EVER). All series hybrids are EREV, REEV or EVER, but not all EREV, REEV or EVER are series hybrids. Series hybrids with particular characteristics are classified as range-extended battery-electric vehicle (BEVx) by the [[California Air Resources Board]].<ref>{{Cite web|title = 2014 BMW i3 Electric Car: Why California Set Range Requirements, Engine Limits|url = http://www.greencarreports.com/news/1087888_2014-bmw-i3-electric-car-why-california-set-range-requirements-engine-limits|website = Green Car Reports| date=23 October 2013 |access-date = 2015-11-22}}</ref>
Electric transmissions were invented by 1903. Mechanical transmissions involve costs via their weight, bulk, noise, cost, complexity, and drain on engine power with every gear-change, affecting both manual and automatic systems. Unlike ICEs, electric motors typically do not require a transmission.
Unlike a parallel hybrid, a series hybrid does not have a mechanical transmission between the engine and wheels. The engine instead acts as an electric generator, attached to the battery via cable. The linkage is engine to battery to electric motor to wheels. In some cases, the generator also directly links to the motor.
This serial arrangement is common in [[diesel–electric transmission|diesel–electric]] [[locomotive]]s and ships (the Russian river ship [[Vandal (tanker)|''Vandal'']], launched in 1903, was the world's first [[Diesel engine|diesel-powered]] and [[diesel–electric transmission|diesel–electric]] powered vessel). In the early 20th century, [[Ferdinand Porsche]] designed several successful vehicles using this arrangement for [[Bombardier Transportation Austria|Lohner-Werke]]. Porsche called it System Mixte. These [[Lohner–Porsche|Lohner–Porsche Mixte Hybrid]] vehicles had a [[wheel hub motor]] arrangement, with motors in two or four wheels. Lohner–Porsche racing cars set speed records.
[[File:Chevrolet Volt charging WAS 2011 833.jpg|thumb|The [[Chevrolet Volt]] operates primarily as a series hybrid.]]
The series hybrid approach isolates the engine from demand, allowing it to operate only at its most efficient speed. The engine can be much smaller, since it does not have to accommodate high speed/acceleration. Traction motors are typically powered only by the battery, which can also be charged from external sources.
[[Nissan]]'s e-Power line ([[Nissan Note#2017 model year update – e-Power|Note]],<ref>{{cite news |url=https://www.greencarreports.com/news/1130444_nissan-note-goes-all-hybrid-in-japan-with-revised-e-power-system-still-due-for-the-us |title=Nissan Note goes all-hybrid in Japan with revised e-Power system still due for the US |author=Edelstein, Stephen |date=December 7, 2020 |work=Green Car Reports |access-date=13 April 2021}}</ref> [[Nissan Serena#C27|Serena]],<ref>{{cite news |url=https://www.greencarcongress.com/2017/10/20171024-serena.html |title=Nissan introducing second non-plug-in e-POWER series-hybrid model: Serena e-POWER |date=October 24, 2017 |work=Green Car Congress |access-date=13 April 2021}}</ref> [[Nissan Kicks#Kicks e-Power|Kicks]],<ref>{{cite news |url=https://www.slashgear.com/2021-nissan-kicks-e-power-ev-debuts-with-an-onboard-generator-18620931/ |title=2021 Nissan Kicks e-Power EV debust with an onboard generator |author=Reyes, Alvin |date=May 18, 2020 |access-date=13 April 2021}}</ref> [[Nissan X-Trail#T33|X-Trail]],<ref>{{cite news|url=https://www.carscoops.com/2022/07/nissan-x-trail-debuts-in-japan-with-second-gen-e-power-hybrid-powertrain/ |title=All-New Nissan X-Trail Debuts In Japan With Second-Gen e-POWER Hybrid Powertrain |author=Pappas, Thanos |date=July 20, 2022 |work=Car |access-date=26 November 2023}}</ref> and [[Nissan Qashqai#J12|Qashqai]])<ref>{{cite news |url=https://www.carmagazine.co.uk/car-news/first-official-pictures/nissan/qashqai/ |title=New Nissan Qashqai: your next family crossover, now with E-Power |author=Scullion, Murray |date=February 18, 2021 |work=Car |access-date=13 April 2021}}</ref> use the engine to drive a generator and the EM57 traction motor.<ref>{{cite web |url=https://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/e_power.html |title=e-POWER |publisher=Nissan Motor Corporation |access-date=13 April 2021}}</ref> [[Mazda]]'s [[Mazda MX-30|MX-30]] is optionally equipped with a range extender.<ref>{{cite news |url=https://arstechnica.com/cars/2021/04/mazdas-electric-mx-30-goes-on-sale-in-the-us-this-fall/ |title=Mazda's electric MX-30 goes on sale in the US this fall |author=Gitlin, Jonathan M. |date=April 14, 2021 |work=Ars Technica |access-date=14 April 2021}}</ref> [[BMW i3 (hatchback)|BMW's i3]] attached the generator only to the battery. ThunderVolt hybrid transit buses<ref>{{cite web |url=https://www.altenergymag.com/articles/04.04.01/thundervolt/contents.html |title=Information on Thundervolt ELFA hybrid-electric drive systems for buses and trucks |date=April 2001 |website=AltEnergyMag |access-date=13 April 2021}}</ref> and transit buses fitted with [[BAE Systems Electronic Systems|BAE Systems]] (formerly [[Lockheed Martin]]) HybriDrive powertrains are also serial hybrids.<ref>{{cite conference |url=https://trid.trb.org/view/658052 |title=HybriDrive Propulsion System: A cleaner, more efficient way to go! |author=Grewe, T |date=May 17–21, 1998 |conference=The 1998 Bus Operations, Technology and Management Conference |location=Phoenix, Arizona |publisher=American Public Transportation System |access-date=13 April 2021}}</ref><ref>{{cite news |url=https://dieselnet.com/news/1999/01lmco2.php |title=Lockheed Martin to deliver more diesel electric propulsion systems for New York City buses |date=January 13, 1999 |work=DieselNet |access-date=13 April 2021}}</ref>
===Electric traction motors=== Electric motors are more efficient than ICEs, with high [[power-to-weight ratio]]s providing torque over a wide speed range. ICEs are most efficient when turning at a constant speed.
ICEs can run optimally when turning a generator. Series-hybrid systems offer smoother acceleration by avoiding gear changes. Series-hybrids incorporate:
* Electric traction only – using only electric motors to turn the wheels. * ICE – turns only a generator. * Generator – turned by the ICE to generate electricity and start the engine. * Battery – energy buffer. * Regenerative braking – The drive motor becomes a generator and recovers energy by converting kinetic to electrical energy, also slowing the vehicle and preventing thermal losses.
In addition:
* May be plugged into the grid to recharge the battery. * [[Supercapacitor]]s assist the battery and recover most energy from braking.
====In detail==== The electric motor may be entirely fed by electricity from the battery or via the generator turned by the ICE, or both. Such a vehicle conceptually resembles a [[diesel–electric transmission|diesel–electric]] [[locomotive]] with the addition of a battery that may power the vehicle without running the ICE and acting as an energy buffer that is used to accelerate and achieve greater speed; the generator may simultaneously charge the battery and power the electric motor that moves the vehicle.
When the vehicle is stopped the ICE is switched off without idling, while the battery provides whatever power is needed at rest. Vehicles at traffic lights, or in slow moving stop-start traffic need not burn fuel when stationary or moving slowly, reducing emissions.
Series-hybrids can be fitted with a [[supercapacitor]] or a [[flywheel]] to store [[regenerative braking]] energy, which can improve efficiency by recovering energy otherwise lost as heat through the braking system. Because a series-hybrid has no mechanical link between the ICE and the wheels, the engine can run at a constant and efficient rate regardless of vehicle speed, achieving higher efficiency (37%, rather than the ICE average of 20%<ref>{{cite web |url=http://courses.washington.edu/me341/oct22v2.htm |title=Improving IC Engine Efficiency |publisher=University of Washington: Energy & Environment – Autumn 2001 |access-date=April 18, 2013}}</ref>) and at low or mixed speeds this could result in ~50% increase in overall efficiency (19% vs 29%).
[[Lotus Cars|Lotus]] offered an engine/generator set design that runs at two speeds, giving 15 kW of electrical power at 1,500 rpm and 35 kW at 3,500 rpm via the integrated electrical generator,<ref>{{cite web |url=http://www.greencarcongress.com/2009/09/lotus-range-extender.html#more |title=Lotus to Introduce Range Extender Engine |publisher=Green Car Congress |date=September 7, 2009}}</ref> used in the Nissan concept [[Infiniti Emerg-e]].
This operating profile allows greater scope for alternative engine designs, such as a [[Microturbines|microturbine]],<ref>{{cite news|first=William|last=Neuman|date=October 11, 2007|work=[[New York Times]]|url=http://cityroom.blogs.nytimes.com/2007/10/11/the-turbine-on-the-bus-goes-purr-purr-purr/ |title=The turbine on the bus goes purr purr purr}}</ref> [[Atkinson cycle#Rotary Atkinson-cycle engine|rotary Atkinson cycle engine]] or [[Linear Combustion Engine|linear combustion engine]].<ref>[http://www.lceproject.org/en/ Linear Combustion Engine Project ] {{Webarchive|url=https://web.archive.org/web/20100606230503/http://www.lceproject.org/en/ |date=2010-06-06 }}. Retrieved April 18, 2013.</ref>
The ICE is matched to the electric engine by comparing the output rates at [[cruising speed]]. Generally, output rates for combustion engines are provided for instantaneous (peak) output rates,<ref>{{Cite web|url=https://www.diygokarts.com/community/?t=9700|title=DIY Go Karts|website=DIY Go Karts|date=5 February 2024 }}</ref> but in practice, these cannot be used.
The use of an [[wheel hub motor|electric motor driving a wheel directly]] eliminates the conventional mechanical transmission elements: gearbox, transmission shafts and differential, and can sometimes eliminate [[Constant-velocity joint|flexible couplings]].
In 1997, Toyota released the first series-hybrid bus sold in Japan.<ref>{{cite web |url=http://www.japantimes.co.jp/news/1997/08/22/news/toyota-debuts-power-hybrid-bus/#.UXAtnMr76dw |title=Toyota debuts power-hybrid bus |work=The Japan Times |date=August 22, 1997 |access-date=April 18, 2013 |archive-date=November 2, 2017 |archive-url=https://web.archive.org/web/20171102162918/https://www.japantimes.co.jp/news/1997/08/22/news/toyota-debuts-power-hybrid-bus/#.UXAtnMr76dw |url-status=dead }}</ref> [[DesignLine Corporation|Designline International]] of Ashburton, New Zealand produces city buses with a [[Microturbine#Microturbines|microturbine]] powered series-hybrid system. [[Wrightbus]] produces series hybrid buses including the [[Wright Gemini 2|Gemini 2]] and [[New Routemaster]]. [[Supercapacitors]] combined with a [[lithium ion]] battery bank have been used by [[AFS Trinity]] in a converted Saturn Vue SUV vehicle. Using [[supercapacitors]] they claim up to 150 mpg in a series-hybrid arrangement.<ref>{{cite web |url=http://afstrinity.com/press/releases/press-release-9-24-08.html |title=AFS Trinity urgees Congress and candidates to support proposed auto stimulus package |publisher=AFS Trinity |date=September 24, 2008}}</ref>
Well known automotive series hybrid models include the variant of the [[BMW i3 (hatchback)|BMW i3]] that is equipped with a range extender. Another example of a series hybrid automobile is the [[Fisker Karma]]. The [[Chevrolet Volt]] is almost a series hybrid, but also includes a mechanical link from the engine to the wheels above 70 mph.<ref>{{Cite web|url=https://www.autoguide.com/auto-news/2010/10/gm-admits-chevy-volts-gasoline-engine-can-power-the-wheels-so-is-it-still-special.html|title=GM Admits Chevy Volt's Gasoline Engine Can Power the Wheels; So is It Still Special?|first=Colum|last=Wood|date=October 12, 2010|website=Autoguide.com}}</ref><ref>{{Cite web|url=https://www.popularmechanics.com/cars/alternative-fuel/cells/chevy-volt-hybrid-drive-system|title=GM Reveals the Volt's Hybrid Drive System|first=Larry|last=Webster|date=October 12, 2010|website=Popular Mechanics}}</ref>
Series-hybrids have been taken up by the aircraft industry. The DA36 E-Star, an aircraft designed by [[Siemens]], [[Diamond Aircraft Industries|Diamond Aircraft]] and [[EADS]], employs a [[series hybrid]] powertrain with the propeller turned by a Siemens 70 kW (94 hp) electric motor. A power sapping propeller speed reduction unit is eliminated. The aim is to reduce fuel consumption and emissions by up to 25 percent. An onboard 40 hp (30 kW) [[Austro Engine]] Wankel rotary engine and generator provides the electricity.
The Wankel was chosen because of its small size, low weight and great power to weight ratio. (Wankel engines also run efficiently at a constant speed of approximately 2,000 RPM which is suited to generator operation. Keeping to a constant/narrow band offsets many of the perceived disadvantages of the Wankel engine in automotive applications.<ref name="telegraph.co.uk">{{cite news| url=https://www.telegraph.co.uk/motoring/news/9550675/Mazda-stays-loyal-to-rotary-engines.html | location=London | work=The Daily Telegraph | title=Mazda stays loyal to rotary engines | date=September 18, 2012}}</ref>)
The electric propeller motor uses electricity stored in batteries, with the engines not operating, to take off and climb reducing sound emissions. The powertrain reduces the weight of the plane by 100 kilos relative to its predecessor. The DA36 E-Star first flew in June 2013, making this the first ever flight of a series hybrid powertrain. Diamond Aircraft state that the technology is scalable to a 100-seat aircraft.<ref>{{cite web|url= http://green.autoblog.com/2011/07/03/siemens-diamond-aircraft-eads-unveil-worlds-first-serial-hybr/ |title=Siemens, Diamond Aircraft, EADS unveil world's first serial hybrid aircraft |publisher=Autoblog |date=2011-07-03 |access-date=2011-07-03}}</ref><ref>{{cite web|url=http://www.greencarcongress.com/2013/06/eads-21030618.html| title=EADS and Siemens enter long-term research partnership for electric aviation propulsion; MoU with Diamond Aircraft | date= 2013-06-18 | access-date=2016-07-18}}</ref>
====In-wheel motors==== If the motors are attached to the vehicle body, [[Constant-velocity joint|flexible couplings]] are required but not if the traction motors are [[wheel motor|integrated into the wheels]]. One disadvantage is that the [[unsprung mass]] increases and suspension responsiveness decreases, which impacts ride and potentially safety. However the impact should be minimal as electric motors in wheel hubs such as [[Hi-Pa Drive]], may be very small and light having exceptionally high [[power-to-weight ratio]]s and braking mechanisms can be lighter as the wheel motors brake the vehicle.
Advantages of individual wheel motors include simplified [[traction control system|traction control]], [[All-wheel drive vehicle|all-wheel drive]] if required and a lower floor (useful for buses and other specialised vehicles (some [[Heavy Expanded Mobility Tactical Truck|8x8 all-wheel drive military vehicles]] use individual wheel motors). [[Diesel–electric transmission|Diesel–electric]] [[locomotive]]s have used this concept (individual motors driving axles of each pair of wheels) for 70 years.<ref>Churella, 28-30</ref>{{full citation needed|date=April 2013}}<ref>{{Cite web |title=Diesel Locomotive Technology |url=http://www.railway-technical.com/diesel.shtml |archive-url=https://web.archive.org/web/20150901062917/http://www.railway-technical.com/diesel.shtml |archive-date=2015-09-01 |access-date=2026-03-28 |website=www.railway-technical.com |language=en-gb}}</ref>
Other measures include lightweight aluminium wheels to reduce the [[unsprung mass]] of the wheel assembly; vehicle designs may be optimized to lower the centre of gravity by locating heavier elements (including battery) at floor level; In a typical road vehicle the power-transmission setup may be smaller and lighter than the equivalent conventional mechanical power-transmission setup, liberating space; the combustion generator set only requires cables to the driving electric motors, increasing flexibility in major component layout spread across a vehicle giving superior weight distribution and maximizing vehicle cabin space and opening up the possibility of superior vehicle designs exploiting this flexibility.
===Series-parallel hybrid=== [[File:Hybridcombined.svg|thumb|Structure of a combined hybrid electric vehicle]]
'''Series-parallel hybrid''' or '''power-split''' are parallel hybrids that incorporate power-split devices, allowing for power paths from the ICE to the wheels that can be either mechanical or electrical. The main principle is to decouple the power supplied by the primary source from the power demanded by the driver.
ICE torque output is minimal at lower RPMs and conventional vehicles increase engine size to meet market requirements for acceptable initial acceleration. The larger engine has more power than needed for cruising. Electric motors produce full torque at standstill and are well-suited to complement ICE torque deficiency at low RPMs. In a power-split hybrid, a smaller, less flexible, and more efficient engine can be used. The conventional [[Otto cycle]] (higher power density, more low-RPM torque, lower [[fuel efficiency]]) is often modified to an [[Atkinson cycle]] or [[Miller cycle]] (lower power density, less low-rpm torque, higher fuel efficiency; sometimes called an Atkinson-Miller cycle). The smaller engine, using a more efficient cycle and often operating in the favorable region of the [[brake specific fuel consumption]] map, significantly contributes to the higher overall efficiency of the vehicle.
Variations of the simple design (pictured at right) found, for example, in the well-known [[Toyota Prius]] are the:
* Fixed-ratio second [[Epicyclic gearing|planetary gearset]] as used in the [[Lexus RX|Lexus RX400h]] and [[Toyota Highlander|Toyota Highlander Hybrid]]. This allows for a motor with less torque but higher power (and higher maximum rotary speed), i.e. higher power density * [[Ravigneaux planetary gearset|Ravigneaux]]<ref>{{cite web|url=http://www.mathworks.com/help/toolbox/physmod/sdl/ref/ravigneauxgear.html |title=Ravigneaux planetary gear set of carrier, sun, planet, and ring wheels with adjustable gear ratios and friction losses - Simulink |publisher=Mathworks.com |access-date=2012-08-01}}</ref>-type planetary gear (planetary gear with 4 shafts instead of 3) and two clutches as used in the [[Lexus GS|Lexus GS450h]]. By switching the clutches, the gear ratio from MG2 (the traction motor) to the wheel shaft is switched, either for higher torque or higher speed (up to 250 km/h / 155 mph) while sustaining better transmission efficiency. This is effectively accomplished in the Generation 3 Prius HSDs (Prius v, Prius Plug-in and Prius c), although the Generation 3 HSD has this second planetary gear set fixed at 2.5:1, rather than switching between 1:1 and 2.5:1 as the "carrier" is held fixed. [[File:2019 Toyota Prius (ZVW50R) 1.8 Hybrid liftback (2018-12-19) 01.jpg|thumb|Power-splitter series-hybrid [[Toyota Prius]] ]] * Two additional planetary gear sets in combination with four clutches to create a [[Two-Mode Hybrid]] configuration able to operate in all-electric, blended electric and ICE, or ICE alone with four fixed gears. Examples of [[Two-Mode Hybrid]]s include the [[General Motors]] [[Two-Mode Hybrid]] full-size trucks and SUVs, the [[BMW X6|BMW X6 ActiveHybrid]]<ref name="an">Krust, Matthias (July 14, 2009). [http://www.autonews.com/apps/pbcs.dll/article?AID=/20090714/COPY02/307149993&AssignSessionID=373348067472168 "BMW, Daimler, GM hybrid alliance nears end"]. [[Automotive News]].</ref> and the [[Mercedes-Benz M Class|Mercedes ML 450 hybrid]].<ref name="an"/>
The Toyota Hybrid System THS / [[Hybrid Synergy Drive]] has a single power-split device (incorporated as a single three-shaft planetary gearset) and can be classified as an Input-Split, since the power of the engine is split at the input to the transmission. This in turn makes this setup very simple in mechanical terms, but has drawbacks of its own. For example, in Generation 1 and Generation 2 HSDs maximum speed is mainly limited by the speed of the smaller electric motor (often functioning as a generator). The Generation 3 HSD separates the ICE-MG1 path from the MG2 path, each with its own, tailored gear ratio (1.1:1 and 2.5:1, respectively, for late Priuses, including the Prius c). The Generation 4 HSD eliminates the second planetary gear set, and places the electric motors on parallel axes, with a combining gear in between these axes, and transfers the combined result to the final drive differential. This is quite similar to Toyota-affiliated [[Aisin Seiki]]'s hybrid system, and saves significant space. [[File:Toyota 1NZ-FXE Engine 01.JPG|thumb|right|Early Hybrid Synergy Drive. Generation 1/Generation 2 (chained) ICE-MG1-MG2 Power Split Device HSD is shown. MG2 ratio permanently set at 1:1.]] [[File:Toyota electronic continuously variable transmission (2010-10-16) 03.jpg|thumb|Late Hybrid Synergy Drive. Generation 3 (chainless) ICE-MG1 Power Split Device/MG2 Motor Speed Reduction Device HSD is shown. MG2 ratio permanently set at 2.5:1.]] [[General Motors]], [[BMW]], and [[DaimlerChrysler]] collaborated on a system named "Two-Mode Hybrid" as part of the [[Global Hybrid Cooperation]]. The technology was released in the fall of 2007 on the [[Chevrolet Tahoe|Chevrolet Tahoe Hybrid]]. The system was also featured on the GMC Graphite SUV concept vehicle at the 2005 [[North American International Auto Show]] in [[Detroit]].<ref>{{cite web|title=The GMC Graphyte — A hybrid SUV concept vehicle |work=GM - GMability Education 9-12: Fuel Cells & Energy |url=http://www.gm.com/company/gmability/edu_k-12/9-12/fc_energy/graphyte.html |archive-url=https://web.archive.org/web/20060116181503/http://www.gm.com/company/gmability/edu_k-12/9-12/fc_energy/graphyte.html |archive-date=January 16, 2006 |url-status=dead }}</ref> [[BYD Auto]]'s [[BYD F3DM|F3DM]] sedan is a series-parallel [[plug-in hybrid]] automobile, which went on sale in China in 2008.<ref>[http://www.chinastakes.com/story.aspx?id=875 "New BYD Hybrid Gets Jump in Electric Car Wars in China"]. China Stakes. December 1, 2008.</ref><ref>{{cite web|last=Yoney |first=Domenick |url=http://www.autobloggreen.com/2009/04/13/chinese-plug-in-hybrid-byd-f3dm-has-sold-just-80-copies-in-fou/ |title=Chinese plug-in hybrid, BYD F3DM, has sold just 80 copies in four months |publisher=Autoblog Green |date=April 13, 2009}}</ref><ref>{{cite news |last=Shirouzu |first=Norihko |url=https://www.wsj.com/articles/SB122392773358329717?mod=googlenews_wsj |title=BYD to Launch Electric Car Sales in China Next Month |work=The Wall Street Journal |date=October 13, 2008}} {{subscription required}}</ref>
The [[Two-Mode Hybrid]] name highlights the drive-train's ability to operate in all-electric (Mode 1, or ''Input-Split'') as well as hybrid (Mode 2, or ''Compound-Split'') modes. The design allows for operation in more than two modes. Two power-split modes are available, along with several fixed-gear (essentially parallel hybrid) regimes. Such a design can be referred to as a multi-regime design.<ref>{{cite journal|last1=Wishart|first1= J.|last2= Zhou|first2= Y.|last3= Dong|first3= Z. |year=2008|title=Review of multi-regime hybrid vehicle powertrain architecture|journal= International Journal of Electric and Hybrid Vehicles|volume=1|issue=3|doi=10.1504/IJEHV.2008.019900|pages= 248–275}}</ref> The Two-Mode Hybrid powertrain design can be classified as a compound-split design, since the addition of four clutches within the transmission allows for multiple configurations of engine power-splitting. In addition to the clutches, this transmission has a second planetary gearset. The objective of the design is to vary the percentage of mechanically vs. electrically transmitted power to cope both with low-speed and high-speed operating conditions. This enables smaller motors to do the job of larger motors when compared to single-mode systems, because the derived electrical peak power is proportional to the width of the continuous variation range. The four fixed gears enable the Two-Mode Hybrid to function like a conventional parallel hybrid under high continuous power regions such as sustained high speed cruising or trailer towing. Full electric boost is available in fixed-gear modes.<ref name="GM Two-Mode">{{cite web|url=http://www.gm.com/experience/fuel_economy/hybrids.jsp|title=Powerfully Efficient: GM Two-Mode Hybrid|publisher=General Motors|archive-url=https://web.archive.org/web/20090225071649/http://www.gm.com/experience/fuel_economy/hybrids.jsp|archive-date=February 25, 2009}}</ref>
==Types by degree of hybridization== {| class="wikitable" style="margin: 1em auto 1em auto;" |- ! Type !! [[Start-stop system]] !! [[Regenerative braking]]<br/>Electric boost !! [[Charge-depleting]] mode !! Rechargeable !! Exhaust regeneration |- | Micro hybrid || {{yes}} || {{no}} || {{no}} || {{no}} || {{no}} |- | [[Mild hybrid]] || {{yes}} || {{yes}} || {{no}}|| {{no}} || {{no}} |- | Dual mild hybrid || {{yes}} || {{yes}} || {{no}}|| {{no}} || {{yes}} |- | Full hybrid || {{yes}} || {{yes}} || {{yes}} || {{no}} || {{no}} |- | Dual full hybrid || {{yes}} || {{yes}} || {{yes}} || {{no}} || {{yes}} |- | [[Plug-in hybrid]] || {{yes}} || {{yes}} || {{yes}} || {{yes}} || {{no}} |- | Dual plug-in hybrid || {{yes}} || {{yes}} || {{yes}} || {{yes}} || {{yes}} |}
===Dual hybrids=== These contain two different energy recovery systems. This is a transversal categorization.
===Micro hybrids=== Micro hybrid (μHEV) is a general term given to vehicles that use some type of [[start-stop system]] to automatically shut off the engine when [[Idle speed|idling]]. Strictly speaking, micro hybrids are not real hybrid vehicles, because they do not rely on two different sources of power.<ref>{{cite web|url=http://www.kfz-tech.de/Engl/HybridBegriffe.htm|title=Hybrid-electro Drives (terms)|publisher=KFZ-tech.de|access-date=13 April 2015}}</ref>
===Mild hybrids=== {{Main|Mild hybrid}} [[File:2006 GMC Sierra Hybrid engine.jpg|right|thumb|Engine compartment of a 2006 [[GMC Sierra]] Hybrid]] Mild hybrids (MHEV) are essentially conventional vehicles with some hybrid hardware, but with limited hybrid features. Typically, they are a parallel hybrid with start-stop and modest levels of engine-assist or regenerative braking. Mild hybrids generally cannot provide all-electric propulsion.
Mild hybrids like the General Motors 2004–2007 Parallel Hybrid Truck (PHT) and the Honda Eco-Assist hybrids are equipped with a [[three-phase]] electric motor mounted within the bell-housing between the engine and transmission, allowing the engine to be turned off whenever the truck is coasting, braking, or stopped, yet restart quickly to provide power. Accessories can continue to run on electrical power while the engine is off, and as in other hybrid designs, regenerative braking recaptures energy. The large electric motor spins up the engine to operating-speeds before injecting fuel.
The 2004–2007 [[Chevrolet Silverado#First-generation Silverado / second-generation Sierra (GMT800; 1999)|Chevrolet Silverado]] PHT was a full-size [[pickup truck]]. Chevrolet was able to get a 10% efficiency improvement by shutting down and restarting the engine on demand and using regenerative braking. The electrical energy was used only to drive accessories such as power steering. The GM PHT used a [[42-volt electrical system|42 volt system]] via three 12 volt vented [[lead–acid battery|lead acid batteries]] connected in series (36V total) to supply the power needed for the startup motor, as well as to power the electronic accessories.
[[General Motors]] then introduced their [[BAS Hybrid]] system, another [[mild hybrid|mild-hybrid]] implementation officially released on the 2007 [[Saturn Vue#Green Line|Saturn Vue Green Line]]. Its "start-stop" functionality operates similarly to the Silverado, although via a belted connection to the motor/generator unit. However the GM [[BAS Hybrid|BAS Hybrid System]] can also provide modest assist under acceleration and during steady driving, and captures energy during regenerative (blended) braking. BAS Hybrid offered as much as a 27% improvement in combined [[fuel efficiency]] in EPA testing of the 2009 Saturn VUE.<ref>{{cite web|url=http://www.fueleconomy.gov/feg/sbs.htm |title=Compare Cars Side-by-Side |publisher=Fueleconomy.gov |access-date=2012-08-01}}</ref> The system can also be found on the 2008–2009 [[Saturn Aura#Aura Green Line|Saturn Aura Green Line]] and the 2008–2010 [[Chevrolet Malibu#Seventh generation (2008)|Chevrolet Malibu]] hybrids.
Another way to offer start/stop is by employing a static start engine. Such an engine requires no starter motor, but employs sensors to determine the exact position of each piston, then precisely timing the injection and ignition of fuel to ''turn over'' the engine.<ref>{{cite journal |last=Kassakian |first=J.G |title=Automotive electrical systems circa 2005 |journal=IEEE Spectrum |year=1996 |volume=33 |issue=8 |pages=22–27 |doi=10.1109/6.511737}}</ref>
Mild hybrids are sometimes called ''power-assist hybrids'' as they use the ICE for primary power, with a torque-boosting electric motor connected to a (largely) conventional power train. The electric motor is mounted between the engine and transmission. It is essentially a large starter motor that operates when the engine needs to be turned over and when the driver "steps on the gas" and requires extra power. The electric motor may also restart the combustion engine and shutting down the main engine at idle, while the enhanced battery system is used to power accessories.{{Citation needed|date=September 2009}} GM announced [[Buick LaCrosse#eAssist|Buick LaCrosse]] and [[Buick Regal#eAssist|Buick Regal]] mild-hybrids dubbed Eassist.
Before 2015, [[Honda]]'s hybrids, including the [[Honda Insight|Insight]], used this design, leveraging their expertise in small, efficient gasoline engines; their system is dubbed [[Integrated Motor Assist]] (IMA). IMA hybrids cannot provide propulsion on electric power alone. However, since the amount of electrical power needed is much smaller, system size is reduced.
Another variation is the [[Saturn Vue#Green Line|Saturn Vue Green Line]] BAS Hybrid system that uses a smaller electric motor (mounted to the side of the engine) and battery pack than the Honda IMA, but functions similarly.
Another variation on this type is [[Mazda]]'s e-4WD system, offered on the [[Mazda Demio]] sold in Japan.<ref>{{cite web |title=Electric 4WD Model Added to Mazda Demio Series |url=https://newsroom.mazda.com/en/publicity/release/2003/200311/1127e.html |website=newsroom.mazda.com |archive-url=https://web.archive.org/web/20210109194851/https://newsroom.mazda.com/en/publicity/release/2003/200311/1127e.html |archive-date=9 January 2021 |date=27 November 2003 |url-status=live}}</ref> This [[front-wheel drive]] vehicle has an electric motor that can drive the rear wheels when extra [[traction (engineering)|traction]] is needed. The system is disengaged in all other driving conditions, so it does not directly enhance performance or economy but allows the use of a smaller and more economical engine relative to total performance.
The [[Genesis G90]] and [[Genesis GV80#GV80 Coupe|Genesis GV80 Coupe]] offer mild hybrid options with an [[electric supercharger]].<ref>{{Cite web|url=https://www.motor1.com/news/582432/2023-genesis-g90-getting-hybrid-v6-with-electric-supercharger/|title=2023 Genesis G90 In US Getting Mild-Hybrid V6 With Electric Supercharger|website=Motor1.com}}</ref><ref>{{Cite web|url=https://www.autoexpress.co.uk/genesis/gv80/361059/big-genesis-gv80-suv-gets-sporty-gv80-coupe-variant-and-facelift|title=Big Genesis GV80 SUV gets sporty GV80 Coupe variant, and a facelift|website=Auto Express}}</ref>
====Dual mild hybrids==== These contain two different energy recovery systems.
The [[Mercedes-Benz C-Class (W206)]], [[Mercedes-AMG SL (R232)|Mercedes-AMG SL 43 (R232)]], the Mercedes-AMG CLE 53, the petrol [[Mercedes-Benz GLC#Second generation (X254/C254; 2022)|Mercedes C254/X254]], and the Porsche 911 Carrera GTS T-Hybrid have an [[electrically-assisted turbocharger]]/[[MGU-H]].<ref>{{Cite web|url=https://www.carmagazine.co.uk/car-news/first-official-pictures/mercedes-benz/cle-amg-53/|title=New 442bhp Mercedes-AMG CLE53: double turbos, six cylinders, all-wheel drive|website=CAR Magazine}}</ref><ref name="mgu-h">{{Cite web |last=Perkins |first=Chris |date=2023-02-10 |title=How Electric Turbochargers Are Changing Internal Combustion |url=https://www.roadandtrack.com/car-culture/a42821665/how-electric-turbochargers-are-changing-internal-combustion/}}</ref><ref>{{Cite web|url=https://www.youtube.com/watch?v=NLvcOjuiZVY|title=Porsche 911 GTS Hybrid (MGU-H) - EXPLAINED|date=May 29, 2024|via=YouTube}}</ref>
===Full hybrids=== {{Distinguish|text = [[Fuel cell vehicle|FCEV]]}} [[File:2006 Mercury Mariner Hybrid engine.jpg|right|thumb|Engine compartment of a 2006 [[Mercury Mariner Hybrid]] ]] A '''full hybrid''' (FHEV or HEV), sometimes also called a '''strong hybrid''', is a vehicle that can run on just the engine, the batteries, or a combination. The [[Toyota Prius]], [[Toyota Camry Hybrid]], [[Ford Escape Hybrid]]/[[Mercury Mariner Hybrid]], [[Ford Fusion Hybrid]]/[[Lincoln MKZ Hybrid]]/[[Mercury Milan Hybrid]], [[Ford C-Max Hybrid]], [[Ford Maverick (2022)|Ford Maverick Hybrid]], [[Kia Optima Hybrid]], [[Toyota Sienna#Fourth generation (XL40; 2020)|Toyota Sienna Hybrid]], as well as the General Motors [[2-mode hybrid]] trucks and SUVs, are examples of this type of hybridization as they can operate on battery power alone. A large, high-capacity battery provides battery-only operation. These vehicles have a split power path that allows more flexibility in the drivetrain by inter-converting mechanical and electrical power. To balance the forces from each portion, the vehicles use a [[differential (mechanical device)|differential]]-style linkage between the engine and motor connected to the head end of the transmission.
The Toyota brand name for this technology is [[Hybrid Synergy Drive]], which is used in the Prius, the [[Toyota Highlander Hybrid|Highlander Hybrid]] [[sport utility vehicle|SUV]] and the [[Camry Hybrid]]. A computer oversees system operation, determining how to mix the power sources. The Prius operations can be divided into six distinct regimes:–
:'''Electric vehicle mode'''—The ICE is off and the battery powers the motor (or charges during regenerative braking). Used for idling when the battery [[state of charge]] (SOC) is high.
:'''Cruise mode'''—The vehicle is cruising (i.e. not accelerating), and the ICE can meet the demand. The power from the engine is split between the mechanical path and the generator. The battery also powers the motor, whose power is summed mechanically with the engine. If the battery state-of-charge is low, part of the power from the generator charges the battery.
:'''Overdrive mode'''—A portion of the [[rotational energy]] produces electricity, because the ICE's full power is not needed to maintain speed. This electrical energy is used to drive the sun gear in the direction opposite its usual rotation. The end result has the ring gear rotating faster than the engine, albeit at lower torque.
:'''Battery charge mode'''—Also used for idling, except that in this case the battery state-of-charge is low and requires charging, which is provided by the engine and generator.
:'''Power boost mode'''—Employed in situations where the engine cannot maintain the desired speed. The battery powers the motor to complement the engine power.
:'''Negative split mode'''—The vehicle is cruising and the battery state-of-charge is high. The battery provides power to both the motor (to provide mechanical power) and to the generator. The generator converts this to mechanical energy that it directs towards the engine shaft, slowing it down (although not altering its torque output). The purpose of this engine "lugging" is to increase the fuel economy of the vehicle.
====Dual full hybrids==== These contain two different energy recovery systems. An example of dual hybrids are [[Formula One car]]s (See [[Formula One engines#2014–2021]] and [[Formula One engines#2022–2025]]). Other examples are the [[Porsche 919 Hybrid]], and the [[Infiniti Q60#Project Black S|Infiniti Project Black S]] which was cancelled.
===Plug-in hybrid=== [[File:Volt charging.jpg|thumb|[[Chevrolet Volt]] charging]] {{Main|Plug-in hybrid}} {{See also|Vehicle-to-grid|Plug-in electric vehicle}} A [[plug-in hybrid electric vehicle]] (PHEV) has two defining characteristics. It:
* Can be plugged into an electrical outlet to be charged. * Can travel powered only by the battery.
They are full hybrids, able to run on battery power; offer greater battery capacity and the ability to recharge from the [[electric power transmission|grid]]; can be either parallel or series designs and are also called ''gas-optional'', or ''griddable'' hybrids. The plug-in hybrid's main benefit is that they can be gasoline-independent for significant distances and also offer the extended ICE range for longer trips. [[Electric Power Research Institute]] research found a lower [[total cost of ownership]] for PHEVs due to reduced service costs and gradually improving battery technology. The "[[well-to-wheel]]" efficiency and emissions of PHEVs compared to gasoline hybrids depends on the grid energy sources (the US grid is 30% [[coal]]; California's grid is primarily [[natural gas]], [[hydroelectric power]], and [[wind power]]). [[File:Byd duel mode engine.jpg|thumb|left|Engine compartment of a [[BYD F3DM]] plug-in hybrid]] [[Prototype]]s of PHEVs, with larger battery packs that can be recharged from the power grid, were built in the U.S., notably at [[Andrew A. Frank|Andy Frank]]'s Hybrid Center<ref>{{cite web | title=Team Fate | publisher=UC-Davis Hybrid Electric Vehicles Group | url=http://www.team-fate.net/ }}</ref> at [[University of California, Davis]]. One production PHEV, the [[Renault Kangoo]], went on sale in France in 2003. [[DaimlerChrysler]] built PHEVs based on the [[Mercedes-Benz Sprinter]] [[van]]. Light Trucks are offered by [[Micro-Vett|Micro-Vett SPA]]<ref>{{cite web|title=Hybrid Daily: Technical Data |publisher=Micro-Vett |url=http://www.micro-vett.it/english/bimodaleing2.html |archive-url=https://web.archive.org/web/20060110114534/http://www.micro-vett.it/english/bimodaleing2.html |archive-date=January 10, 2006 |url-status=dead }}</ref> the so-called Daily Bimodale.
The California Cars Initiative converted the 2004 and newer Toyota Prius to become a prototype of what it calls PRIUS+. With the addition of {{convert|300|lb|kg|abbr=on|order=flip}} of [[lead–acid batteries]], the PRIUS+ achieved roughly double the gasoline [[fuel economy in automobiles|mileage]] of a standard Prius and could make trips of up to {{convert|10|mi|km|order=flip}} using only electric power.<ref>{{cite web | title=How We Green-Tuned an '04 Prius into a PRIUS+ Plug-In Hybrid!| work=CalCars | url=http://www.calcars.org/priusplus.html | access-date=April 18, 2013}}</ref>
Chinese battery manufacturer and automaker [[BYD Auto]] released the [[BYD F3DM|F3DM]] compact [[Sedan (automobile)|sedan]] to the Chinese fleet market on December 15, 2008,<ref name=F3DM>Crippen, Alex (December 15, 2008). [https://www.cnbc.com/2008/12/15/warren-buffetts-electric-car-hits-the-chinese-market-but-rollout-delayed-for-us-europe.html "Warren Buffett's Electric Car Hits the Chinese Market, But Rollout Delayed For U.S. & Europe"]. CNBC.</ref><ref name=bwf3dm>Balfour, Frederik (December 15, 2008). [http://www.businessweek.com/globalbiz/content/dec2008/gb20081215_913780.htm "China's First Plug-In Hybrid Car Rolls Out"] {{webarchive|url=https://web.archive.org/web/20081220105009/http://www.businessweek.com/globalbiz/content/dec2008/gb20081215_913780.htm |date=2008-12-20 }}. ''Business Week''.</ref> later replaced by the [[BYD Qin]] plug-in hybrid.<ref>{{cite web|url=http://www.greencarreports.com/news/1075547_byd-chin-worlds-first-plug-in-hybrid-updated-and-renamed|title=BYD Chin: World's First Plug-In Hybrid, Updated And Renamed|author=Voelcker, John|publisher=Green Car Reports|date=April 20, 2012}}</ref><ref>{{cite web|url=http://green.autoblog.com/2012/04/20/byds-beijing-motor-show-line-up-includes-chin-dual-mode-remote/|title=BYD's Beijing Motor Show line-up includes Chin Dual Mode, remote-controlled F3|author=Blanco, Sebastian|publisher=Autoblog Green|date=April 20, 2012}}</ref>
General Motors began deliveries of the [[Chevrolet Volt]] in the United States in December 2010,<ref name="R1"/> and its sibling, the Opel Ampera, was released in Europe by early 2012.<ref name=FirstRetailDelivery>{{cite web|last=Chambers|first=Nick|url=http://www.plugincars.com/first-chevy-volts-reach-customers-will-out-deliver-nissan-december-106575.html|title=First Chevy Volts Reach Customers, Will Out-Deliver Nissan in December|publisher=plugincars.com|date=December 16, 2010}}</ref><ref>{{cite web|url=http://media.opel.com/media/intl/en/opel/news.detail.html/content/Pages/news/intl/en/2012/opel/02_21_opel_ampera_first_customer|title=Opel Ampera: First Customers Take Delivery|publisher=Opel Europe|date=February 21, 2012}}</ref> {{As of|2012|11}}, other plug-in hybrids available in several markets were the [[Fisker Karma]], [[Toyota Prius Plug-in Hybrid]] and [[Ford C-Max Energi]].
{{As of|2012|10}}, the best selling PHEV is the Volt, with more than 33,000 units of the Volt/Ampera family sold worldwide since December 2010, led by US sales of 27,306,<ref name=PEVsalesUS0712>{{cite web|url=http://www.greencarreports.com/news/1078116_july-plug-in-electric-car-sales-volt-steady-leaf-lethargic-again|title=July Plug-In Electric Car Sales: Volt Steady, Leaf Lethargic (Again)|author=Voelcker, John|publisher=Green Car Reports|date=August 1, 2012}}</ref><ref name=PEVSalesUS1012>{{cite web|url=http://insideevs.com/october-2012-plug-in-electric-vehicle-sales-report-card/|title=October 2012 Plug-In Electric Vehicle Sales Report Card|author=Cole, Jay|publisher=Inside EVs|date=November 1, 2012}}</ref> followed by the Netherlands with 2,175 Amperas sold through October 2012.<ref name=NetherSales2012>{{cite web|url=http://www.raivereniging.nl/markt-informatie/statistieken/verkoopstatistieken.aspx |title=Autoverkopen mei 2012 dalen met 4,4 procent |language=nl |trans-title=Car sales in May 2012 decreased by 4.4 percent |author=RAI |publisher=RAI Vereniging |date=2012-06-04 |access-date=2012-08-05 |url-status=dead |archive-url=https://web.archive.org/web/20140328183047/http://www.raivereniging.nl/markt-informatie/statistieken/verkoopstatistieken.aspx |archive-date=2014-03-28 }} ''Download pdf file for detailed sales in 2011 and 2012 CYTD''.</ref><ref name=NetherSales1012>{{cite web|url=http://www.autoweek.nl/verkoopcijfers.php?verkoopjaar=2012&maand=10 |title=Verkoopcijfers oktober 2012 - Modellenoverzicht |language=nl |trans-title=Sales October 2012 - Models overview |author=RAI |publisher=Auto Week Netherlands |date=October 2012 |access-date=2012-11-01 |url-status=dead |archive-url=https://web.archive.org/web/20121105075038/http://www.autoweek.nl/verkoopcijfers.php?verkoopjaar=2012&maand=10 |archive-date=2012-11-05 }} ''Table shows September and October 2012 sales''.</ref> The Prius Plug-in Hybrid had sold 21,600 units sold worldwide through October 2012, with US sales of 9,623 units, followed by Japan with 9,500 units.<ref name=PEVSalesUS1012/><ref name=PiPSales1012>{{cite web|url=http://www2.toyota.co.jp/en/news/12/11/1108_1.html|title=Cumulative Sales of TMC Hybrids Top 2 Million Units in Japan|publisher=Toyota|date=November 8, 2012|access-date=November 24, 2012|archive-date=November 11, 2012|archive-url=https://web.archive.org/web/20121111065020/http://www2.toyota.co.jp/en/news/12/11/1108_1.html|url-status=dead}}</ref> More recently, the 4xe variants of the [[Jeep Wrangler (JL)|Jeep Wrangler]] and [[Jeep Grand Cherokee#Fifth generation (WL; 2021)|Jeep Grand Cherokee]] have become the best-selling PHEVs in the U.S., respectively selling 67,429 and 45,684 units in calendar 2023.<ref>{{cite web |url=https://insideevs.com/news/715209/stellantis-phev-sales-2024q1/ |title=U.S.' King Of Plug-In Hybrids Set Another PHEV Sales Record In Q1 2024 |first=Mark |last=Kane |work=Inside EVs |date=April 8, 2024 |access-date=November 6, 2024}}</ref>
====Dual plug-in hybrids==== These contain two different energy recovery systems. Examples of such systems include the [[Mercedes-AMG ONE]], is a plug-in dual hybrid. The [[Mercedes-Benz C-Class (W206)]] and the [[Mercedes-Benz GLC#Second generation (X254/C254; 2022)|Mercedes C254/X254]] also have an [[electrically-assisted turbocharger]]/[[MGU-H]].<ref name="ams-2021-02">{{cite web|last=Holger Wittich, Patrick Lang|date=2021-02-22|title=Neue Mercedes C-Klasse (W206)|url=https://www.auto-motor-und-sport.de/neuheiten/mercedes-c-klasse-w206-infos-daten-marktstart-preise|publisher=[[auto motor und sport]]}}</ref><ref name="mgu-h" />
==Types by power source==
===Electric-internal combustion engine hybrid=== There are many ways to create an electric-Internal Combustion Engine (ICE) hybrid. The variety of electric-ICE designs can be differentiated by how the electric and combustion portions of the powertrain connect, at what times each portion is in operation, and what percent of the power is provided by each hybrid component. Two major categories are '''series hybrids''' and '''parallel hybrids''', though '''parallel designs''' are most common today.
Most hybrids, no matter the specific type, use [[regenerative braking]] to recover energy when slowing down the vehicle. This simply involves driving a motor so it acts as a generator.
Many designs also shut off the internal combustion engine when it is not needed in order to save energy. That concept is not unique to hybrids; [[Subaru]] pioneered this feature in the early 1980s, and the [[Volkswagen Lupo|Volkswagen Lupo 3L]] is one example of a conventional vehicle that shuts off its engine when at a stop. Some provision must be made, however, for accessories such as [[air conditioning]] which are normally driven by the engine. Furthermore, the lubrication systems of internal combustion engines are inherently least effective immediately after the engine starts; since it is upon startup that the majority of engine wear occurs, the frequent starting and stopping of such systems reduce the lifespan of the engine considerably.{{Dubious|reason=frequent starting engines are already warm and lubricated|date=May 2014}} Also, start and stop cycles may reduce the engine's ability to operate at its optimum temperature, thus reducing the engine's efficiency.
[[File:Hybridfuelcell.svg|thumb|Structure of a fuel cell hybrid electric vehicle]]
===Electric-fuel cell hybrid=== [[Fuel cell]] vehicles are often fitted with a battery or supercapacitor to deliver peak acceleration power and to reduce the size and power constraints on the fuel cell (and thus its cost); this is effectively also a series hybrid configuration.
===Internal combustion engine-hydraulic hybrid=== [[File:Chrysler_Pacifica_Hybrid_WAS_2017_1684.jpg|thumb|left|[[Chrysler]] offers the [[Chrysler Pacifica (RU)|Pacifica]] minivan as a plug-in hybrid]] A [[hydraulic hybrid]] vehicle uses hydraulic and mechanical components instead of electrical. A [[variable displacement pump]] replaces the electric motor/generator. A [[hydraulic accumulator]] stores energy. The vessel typically carries a flexible bladder of pre-charged pressurized nitrogen gas. Pumped hydraulic fluid is compressed against the bladder storing the energy in the compressed nitrogen gas. Some versions have a piston in a cylinder rather than a pressurized bladder. The hydraulic accumulator is potentially cheaper and more durable than batteries. Hydraulic hybrid technology was originally implemented in Germany in the 1930s. Volvo Flygmotor used petro-hydraulic hybrids experimentally in buses from the early 1980s.
The initial concept involved a giant [[flywheel]] (see [[Gyrobus]]) for storage connected to a hydrostatic transmission. The system is under development by [[Eaton Corporation|Eaton]] and several other companies, primarily in heavy vehicles like buses, trucks and military vehicles. An example is the Ford F-350 Mighty Tonka concept truck shown in 2002. It features an Eaton system that can accelerate the truck to highway speeds.
The system components were expensive, which precluded installation in smaller trucks and cars. A drawback was that the power motors were not efficient enough at part load. Focus switched to smaller vehicles. A British company, [[Artemis Intelligent Power]], made a breakthrough by introducing an electronically controlled hydraulic motor/pump that is efficient at all ranges and loads, making small applications of petro-hydraulic hybrids feasible.<ref>{{cite web|url=http://www.artemisip.com/our-technology |title=Our Technology |publisher=Artemis Intelligent Power |access-date=April 18, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130729061859/http://artemisip.com/our-technology |archive-date=July 29, 2013 }}</ref> The company converted a BMW car to prove viability. The BMW 530i gave double the MPG in city driving compared to the standard car. The test used the standard 3,000 cc engine. Petro-hydraulic hybrids allows downsizing an engine to average power usage, not peak power usage. Peak power is provided by the energy stored in the accumulator.<ref>{{cite web |url=http://www.artemisip.com/applications/on-road |title=Applications – On-road |publisher=Artemis Intelligent Power |access-date=April 18, 2013 |archive-url=https://web.archive.org/web/20150525063540/http://www.artemisip.com/applications/on-road |archive-date=May 25, 2015 |url-status=dead }}</ref>
The kinetic braking energy recovery rate is higher and therefore the system is more efficient than 2013-era battery charged hybrids, demonstrating a 60% to 70% increase in economy in EPA testing.<ref>{{cite web|url=http://www.epa.gov/oms/technology/420f05006.pdf |archive-url=https://web.archive.org/web/20100402080301/http://www.epa.gov/OMS/technology/420f05006.pdf |url-status=dead |archive-date=April 2, 2010 |title=EPA Announces Partnership to Demonstrate World's First Full Hydraulic Hybrid Urban Delivery Vehicle |publisher=EPA |date=February 2005 |access-date=April 18, 2013}}</ref> In EPA tests a hydraulic hybrid Ford Expedition returned {{convert|32|mpgus|L/100 km|sigfig=2|abbr=on}} in urban driving and {{convert|22|mpgus|L/100 km|sigfig=2|abbr=on}} on the highway.<ref>{{cite web|last=Vanzieleghem |first=Bruno |url=http://www.autobloggreen.com/2006/06/15/capturing-the-power-of-hydraulics |title=Capturing the power of hydraulics |publisher=Autoblog Green |date=June 15, 2006}}</ref>
One research company's goal was to create a fresh design to improve the packaging of gasoline-hydraulic hybrid components. All bulky hydraulic components were integrated into the chassis. One design claimed to reach 130mpg in tests by using a large hydraulic accumulator that is also the structural chassis. The hydraulic driving motors are incorporated within the wheel hubs and reversing to recover braking energy. The aim is 170 mpg in average driving conditions. Energy created by shock absorbers and kinetic braking energy, that normally would be wasted, assists in charging the accumulator. An ICE sized for average power use charges the accumulator. The accumulator is sized to run the car for 15 minutes when fully charged.<ref>{{cite web |last=Proefrock |first=Philip |url=http://inhabitat.com/hybrid-hydraulic-drive-vehicle-promises-170-mpg/ |title=Hybrid Hydraulic Drive Vehicle Promises 170 MPG |publisher=Inhabitat |date=March 25, 2010}}</ref><ref>{{cite web |last=Turpen |first=Aaron |url=http://www.torquenews.com/1080/ingocar-valentin-tech-shatters-way-we-think-about-cars |title=INGOCAR from Valentin Tech shatters the way we think about cars |publisher=Torque News |date=February 15, 2012}}</ref><ref>{{cite web|url=http://www.valentintechnologies.com/default.asp |title=170 MPG Ingocar |publisher=Valentin Technologies, Inc |access-date=April 18, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130421115904/http://www.valentintechnologies.com/default.asp |archive-date=April 21, 2013 }}</ref>
In January 2011, Chrysler announced a partnership with the EPA to design and develop an experimental gasoline-hydraulic hybrid powertrain suitable for use in passenger cars. Chrysler adapted an existing production minivan to the powertrain.<ref>{{cite web |last=Hanlon |first=Mike |url=http://www.gizmag.com/chrysler-announces-development-of-hydraulic-hybrid-technology-for-cars/17686/ |title=Chrysler announces development of hydraulic hybrid technology for cars |publisher=Gizmag |date=January 26, 2011}}</ref><ref>{{cite web|url=http://yosemite.epa.gov/opa/admpress.nsf/0/837c1d022dba18448525781d005995be?OpenDocument |archive-url=https://archive.today/20120805232854/http://yosemite.epa.gov/opa/admpress.nsf/0/837c1d022dba18448525781d005995be?OpenDocument |url-status=dead |archive-date=August 5, 2012 |title=EPA and Chrysler to Take Latest Hybrid Technology from Lab to Street/Partnership to adapt fuel efficient technology |publisher=EPA |date=January 19, 2011}}</ref><ref>{{cite web|url=http://epa.gov/otaq/technology/research/research-hhvs.htm |archive-url=https://archive.today/20120709024214/http://epa.gov/otaq/technology/research/research-hhvs.htm |url-status=dead |archive-date=July 9, 2012 |title=Hydraulic Hybrid Research |publisher=EPA |access-date=April 18, 2013}}</ref><ref>{{cite web|url=http://epa.gov/otaq/technology/research/demonstration-vehicles.htm |archive-url=https://web.archive.org/web/20101109134303/http://epa.gov/otaq/technology/research/demonstration-vehicles.htm |url-status=dead |archive-date=November 9, 2010 |title=Demonstration Vehicles |publisher=EPA |access-date=April 18, 2013}}</ref><ref>{{cite web|url=http://www.greencarcongress.com/2013/09/20130924-chrysler.html|title=Chrysler Group files S-1 for IPO; snapshot of R&D priorities; exploring a light-duty hydraulic hybrid|date=2013-09-24|access-date=2016-07-18}}</ref>
NRG Dynamix of the U.S.A. claimed its approach reduced cost by one-third compared with electric hybrids and added only 300 lbs (136 kg) to vehicle weight vs. 1,000 lbs (454 kg) for electric hybrids. The company claimed a standard pickup vehicle powered by a 2.3-litre, 4-cylinder engine achieved 14 mpg (16.8 L/100 km) in city driving. Using the petro-hydraulic setup fuel economy reached "the mid 20s".<ref>{{cite web|url=http://wardsauto.com/vehicles-amp-technology/new-hydraulic-hybrid-system-claims-big-mpg-boost | title=New Hydraulic Hybrid System Claims Big MPG Boost | author=David C. Smith | editor=WardsAuto|date= 2012-08-06 |access-date=2016-07-18}}</ref>
===Internal combustion engine-pneumatic=== Compressed air can power a hybrid car with a gasoline compressor to provide the power. [[Motor Development International]] in France was developing such air-powered cars. A team led by Tsu-Chin Tsao, a [[UCLA]] mechanical and aerospace engineering professor, collaborated with engineers from Ford to get pneumatic hybrid technology up and running. The system is similar to that of a hybrid-electric vehicle in that braking energy is harnessed and stored to assist the engine as needed during acceleration.
===Human power-environmental power=== Many land and water vehicles use human power combined with a further power source. Common are parallel hybrids, e.g. a sailboat with oars, [[motorized bicycle]]s or a [[human-electric hybrid vehicle]] such as the [[Twike]]. Some series hybrids exist. Such vehicles can be [[tribrid vehicle]]s, combining three power sources e.g. on-board solar cells, grid-charged batteries and pedals.
==Hybrid vehicle operation modes== Hybrid vehicles can be used in different modes. The figure shows some typical modes for a parallel hybrid configuration. [[File:Hybrid modes.gif|thumb|center|500px]] {{Clear}}
==Hybrid drivetrain topology== P stands for Position. If there are multiple electric motors in different locations, may be written as P1 + P3 or P0 + P2.5 + P4.
Location of electric motor(s) in drivetrain: * P0 – beside, inside or in front of engine (Ex: ''Belt-Alternator-Starter ([[BAS hybrid|BAS]]) or Integrated Starter-Generator ([[Integrated starter-generator|ISG]]))'' * P1 – engine output shaft (Ex: ''Integrated motor-generator (IMG), integrated motor assist ([[Integrated Motor Assist|IMA]]), flywheel assist system (FAS)''<ref>{{Cite web |title=Parallel Hybrid Configurations Supported |url=https://vibratesoftware.com/about-us/parallel-hybrid-configurations/ |access-date=2024-07-26 |website=Vibrate Software, Inc. |language=en-US}}</ref>'')'' * P2 – between engine and transmission * P2.5 – inside transmission * P3 – transmission output shaft * P4 – rear axle * P5 – inside the wheel(s) or propeller(s)<ref>{{Cite web|url=https://www.researchgate.net/publication/367071291_Energy_Flow_and_Electric_Drive_Mode_Efficiency_Evaluation_of_Different_Generations_of_Hybrid_Vehicles_under_Diversified_Urban_Traffic_Conditions/fulltext/63c015fc56d41566df5e406e/Energy-Flow-and-Electric-Drive-Mode-Efficiency-Evaluation-of-Different-Generations-of-Hybrid-Vehicles-under-Diversified-Urban-Traffic-Conditions.pdf|title=Energy Flow and Electric Drive Mode Efficiency Evaluation of Different Generations of Hybrid Vehicles under Diversified Urban Traffic Conditions}}</ref>
==Aftermarket options== Often, an [[Aftermarket (automotive)|aftermarket]] powertrain can be added to a vehicle. The aftermarket solution is used when the user delivers [[Electric vehicle conversion|glider]] ([[rolling chassis]]) and the hybrid (two engines) or all-electric (only an electric motor) powertrain kit to the [[automaker]] and receives the vehicle with the tech installed. An (electric or hybrid) powertrain can be added to a glider<ref>{{cite web |url=http://www.nrel.gov/docs/fy05osti/37567.pdf |title=Energy Storage Fuel Cell Vehicle Analysis: Preprint |publisher=National Renewable Energy Laboratory |date=April 2005}}</ref> by an aftermarket installer.
In 2013 a [[University of Central Florida]] design team, ''On the Green'', worked to develop a bolt-on hybrid conversion kit to transform an older model vehicle into a gas-electric hybrid.<ref>[http://ucfhybridcart.wordpress.com/ On the Green]. Retrieved April 18, 2013.</ref>
A conversion of a 1966 Mustang was demonstrated by an engineer in California. The system replaced the alternator with a 12 kW (30 kW peak) brushless electric motor. Gas mileage and power improved.<ref>[http://www.howtobuildahybrid.com/ How To Build A Hybrid] {{Webarchive|url=https://web.archive.org/web/20130604152730/http://howtobuildahybrid.com/ |date=2013-06-04 }}. Retrieved April 18, 2013.</ref>
There are [[hub motor]]s that can be fitted in the wheel,<ref>{{Cite web |title=EV FOR EVERYONE |url=https://www.orbiselectric.com/ |access-date=2024-03-20 |website=ORBIS ELECTRIC (Copy) |language=en-US}}</ref> or between the wheel and brake rotor<ref>{{Cite web |author=Staff Reporter |date=2023-09-12 |title=RMIT student wins James Dyson Award for new electric motor retrofit solution |url=https://www.aumanufacturing.com.au/rmit-student-wins-james-dyson-award-for-new-electric-motor-retrofit-solution |access-date=2024-03-20 |website=Australian Manufacturing Forum |language=en-AU}}</ref> of internal combustion vehicles to convert them to hybrid [[individual wheel drive]] (IWD).
==See also== * [[Battery electric vehicle]] * [[Electric vehicle]] ** [[Electric vehicle battery#Battery architecture and integration|Battery architecture and integration]] * [[Engine control unit]] * [[Hybrid electric vehicle]]
==References== {{Reflist}}
==External links== * {{HowStuffWorks|3290-hybrid-cars-need-special-mechanics-video|Hybrid Cars Need Special Mechanics}} * [https://web.archive.org/web/20080119112528/http://www.ecogeek.org/content/view/1298/ The Rise of the REEV] * [https://web.archive.org/web/20061210194839/http://www.ecoworld.com/blog/2006/11/10/serial-hybrids-are-here/ Serial Hybrids Are Here - Ecoworld.com] * [http://science.discovery.com/fansites/discoveriesthisweek/videogallery/videogallery.html?myClip=dtw_aircar Air Car video] {{Webarchive|url=https://web.archive.org/web/20061024154644/http://science.discovery.com/fansites/discoveriesthisweek/videogallery/videogallery.html?myClip=dtw_aircar |date=2006-10-24 }} * [https://web.archive.org/web/20100906145407/http://www.zeroshift.com/transmission-technology/Hybrid-Electric-Vehicle-Transmissions.html Zeroshift hybrid and electric vehicle Transmission (EV transmission) Systems]
{{Powertrain}}
{{DEFAULTSORT:Hybrid Vehicle Drivetrain}} [[Category:Engines]] [[Category:Hybrid powertrain| ]] [[Category:Hybrid vehicles]]