{{short description|Type of wireless power transfer}} {{redirect|Wireless charging|conductive charging with pads instead of wires|conductive wireless charging}} thumb|The primary coil in the charger induces a current in the secondary coil in the device being charged.

'''Inductive charging''', also known as '''wireless charging''' or '''cordless charging''', is a type of wireless power transfer. It uses electromagnetic induction to provide electricity to portable devices. Inductive charging is also used in vehicles, power tools, electric toothbrushes, and medical devices. The equipment can be placed over an inductive pad free of any electrical contacts such as a dock or plug.

Inductive charging transfers energy through inductive coupling: alternating current passes through an induction coil, generating a fluctuating magnetic field, which creates an induced alternating electric current in a nearby secondary coil. The alternating current can be rectified to a direct current which charges a battery or provides operating power.<ref name="edn-2019">{{citation |url=https://www.edn.com/electronics-blogs/brians-brain/4461755/Wireless-charging--The-state-of-disunion |title=Wireless charging: The state of disunion |date=March 28, 2019 |author=Brian Dipert |website=Electrical Design Magazine}}</ref><ref name="Treffers" />

Greater distances between sender and receiver coils, such as those required for wirelessly charging electric vehicles, can be achieved with resonant inductive coupling. The alternating current of the system can use a resonance frequency tuned with capacitors to create a transmitter and receiver LC circuit with a specific resonance frequency. The frequency is chosen depending on the distance desired for optimal efficiency,<ref name="edn-2019" /> and as of 2025 the frequency is commonly 85&nbsp;kHz. Some systems use inductive loops made of Litz wire surrounding ferrite cores.<ref name="ENRX-Litz">{{citation |contribution=Integrating Electric Road Systems for Reliable EV Charging |author=Sergio A. Perez Romero (ENRX) |year=2026 |display-authors=etal |title=17th World Congress on Road Winter Service, Resilience and Decarbonization |publisher=PIARC}}</ref> Charging efficiency is sensitive to lateral, longitudinal, and vertical misalignment.<ref>{{citation |title=Review and Evaluation of Automated Charging Technologies for Heavy-Duty Vehicles |doi=10.3390/wevj15060235 |date=May 29, 2024 |journal=World Electric Vehicle Journal |author=Emma Piedel |display-authors=etal |volume=15 |issue=6 |page=235 |doi-access=free }}</ref> Misalignment of more than {{cvt|3|cm|in}} can severely lower power transfer.<ref name="Norway-2025">{{citation |author=P. P. Revheim (AtB)|contribution=The performance of inductive ERS in harsh winter climates: A Trondheim pilot study |year=2026 |display-authors=etal |title=17th World Congress on Road Winter Service, Resilience and Decarbonization |publisher=PIARC}}</ref> Some systems align their coils by having the receiver coils mounted on a movable arm that can be lowered closer to the transmitter coils, for example it can be lowered from the underside of a truck closer to a transmitter coil on the ground.<ref>{{citation |url=https://www.youtube.com/watch?v=K20LV6YwLiQ |title=37 - The Future of Wireless EV Charging: Insights from Electreon's Charlie Levine |date=December 23, 2024 |website=YouTube |author=Insider's Guide to Energy podcast |at=3 minutes and 14 seconds}}</ref> {{TOC limit|3}} ==Applications== Applications of inductive charging can be divided broadly into low power and high power. Low power applications generally target consumer electronic devices such as cell phones, handheld devices, computers, and similar devices which normally require power below 100 watts. The AC utility frequency of 50 or 60 hertz is often used,<ref>{{cite web |last1=Dipert |first1=Brian |title=Wireless charging: The state of disunion |date=28 March 2019 |url=https://www.edn.com/wireless-charging-the-state-of-disunion/ |access-date=12 September 2021}}</ref> or in the case of Qi-compliant devices, frequencies in the range of 87 to 205 kHz are typical.<ref>{{cite web |title=Qi Specification Introduction |page=11 |publisher=Wireless Power Consortium |url=https://www.wirelesspowerconsortium.com/knowledge-base/specifications/download-the-qi-specifications.html |archive-url=https://web.archive.org/web/20191105114155/https://www.wirelesspowerconsortium.com/knowledge-base/specifications/download-the-qi-specifications.html |url-status=dead |archive-date=November 5, 2019 |access-date=8 September 2023 |language=en}}</ref> Some methods, such as resonant inductive coupling, can maintain charging at a distance of a few inches between the transmitter and receiver coil,<ref name="Madzharov et al, 2017" /> though foreign objects pose a fire or burn risk if metals or organisms are between the active coils for high-power systems.<ref name="SAE-DWPT-standards" /> High power inductive charging generally refers to power above 1 kilowatt. Such power is required for electric vehicles, and some implementations reach 300 kilowatts or higher. High-power inductive charging systems use resonant inductive coupling for higher efficiency. These systems are usually implemented in the long wave range of frequencies in the tens of kilohertz, commonly 85&nbsp;kHz<ref name="ENRX-Litz" /> as the regulatory allowable noise levels are higher at this range than surrounding ranges.<ref>{{citation |url=https://www.editions-rgra.com/revue/1014/recherche-et-innovation/charge-you-drive-experimentation-sur-autoroute-dune-solution-de |title=Charge As You Drive : expérimentation sur autoroute d’une solution de recharge dynamique |date=February 2026 |journal=RGRA N° 1014}}</ref> Short wave frequencies can enhance the system's efficiency and size but they're not used because they would create radio interference worldwide.<ref>{{citation |last1=Regensburger |first1=Brandan |last2=Kumar |first2=Ashish |last3=Sreyam |first3=Sinhar |last4=Khurram |first4=Afridi |title=2018 IEEE 19th Workshop on Control and Modeling for Power Electronics (COMPEL) |chapter=High-Performance 13.56-MHz Large Air-Gap Capacitive Wireless Power Transfer System for Electric Vehicle Charging |publisher=IEEE |doi=10.1109/COMPEL.2018.8460153 |year=2018|pages=1–4 |isbn=978-1-5386-5541-2 |s2cid=52285213 }}</ref> High power at 85&nbsp;kHz raise the concern of electromagnetic compatibility and radio frequency interference over background noise levels at ranges of up to {{cvt|300|km|mi}}.<ref>{{citation |url=https://emobilitycentre.se/wp-content/uploads/2022/11/Underbilaga_7_FOI-R-4808-SE-Interference-Risks-from-WPT.pdf|author=Karina Fors|title=Interference Risks from Wireless Power Transfer for Electric Vehicles|website=Totalförsvarets forskningsinstitut|date=December 2019}}</ref>

Inductive charging offers protected connections free of need of corrosion protection. Induction circuits offer protection from faults such as short circuits due to insulation failure, especially where connections are made or broken frequently.<ref name="Madzharov et al, 2017" /> Without the need to constantly plug and unplug the device, there is significantly less wear and tear on the socket of the device and the attaching cable.<ref name="Madzharov et al, 2017" /> For embedded medical devices, the transmission of power via a magnetic field passing through the skin avoids the infection risks associated with wires penetrating the skin.<ref>“Wireless Power For Medical Devices.” MDDI Online, 7 Aug. 2017, www.mddionline.com/wireless-power-medical-devices.</ref> Automatic operation of inductive charging in roads can allows vehicles to operate without charging stops through opportunity charging over inductive coils embedded in the road.<ref>{{Cite news|url=https://www.technologyreview.com/s/607902/the-case-for-building-roads-that-can-charge-electric-cars-on-the-go/|title=Do you really need wireless charging roads?|last=Condliffe|first=Jamie|work=MIT Technology Review|access-date=2018-10-04|language=en}}</ref>

==Power losses and waste heat== thumb|Charging with induction (left image) creates more waste heat than using a cable (right image). Due to the lower efficiency of inductive charging compared to conductive charging, devices took 15 percent longer to charge when supplied power is the same amount when tested in 2018.<ref>{{Cite news|url=https://www.nytimes.com/2018/10/03/technology/personaltech/wireless-charging-pros-cons.html|title=Wireless Charging Is Here. So What Is It Good For?|work=The New York Times |date=3 October 2018 |access-date=2018-10-04|language=en|last1=Chen |first1=Brian X. }}</ref> An amateur 2020 analysis of energy use conducted with a Pixel 4 found that a wired charge from 0 to 100 percent consumed 14.26 Wh (watt-hours), while a wireless charging stand used 19.8 Wh, an increase of 39%. Using a generic wireless charging pad and mis-aligning the phone produced consumption up to 25.62 Wh, or an 80% increase. The analysis noted that while this is not likely to be noticeable to individuals, it has negative implications for greater adoption of smartphone wireless charging.<ref>{{cite news |last=Ravenscraft |first=Eric |title=Wireless Charging Is a Disaster Waiting to Happen |work=onezero |publisher=Medium |url=https://onezero.medium.com/wireless-charging-is-a-disaster-waiting-to-happen-48afdde70ed9 |date=August 5, 2020 |access-date=2020-08-27}}</ref>{{Better source needed|date=January 2026}}

Inductive chargers produce more waste heat than wired chargers, which may negatively impact battery longevity.<ref>{{cite news|last1=Bradshaw|first1=Tim|title=Review: the joys of smartphone wireless chargers|work=Financial Times|archive-url=https://web.archive.org/web/20190919035555/https://www.ft.com/content/871843e8-aa78-11e7-93c5-648314d2c72c|url=http://www.ft.com/content/871843e8-aa78-11e7-93c5-648314d2c72c|archive-date=September 19, 2019}}</ref>{{Better source needed|reason=FT article only passingly mentions heat problem and provides neither specific numbers nor concrete examples|date=April 2022}} Waste heat is a concern for high-power implementations of inductive charging for transportation. Trials in France in 2023 found risk of thermal damage to the road under regular operating conditions due to the induction coils exceeding temperatures of {{convert|100|C|0}}.<ref name="Hornych-AIPCR-2023" />

==Standards== [[File:Wireless Charging Pad 2018.jpg|thumb|Wireless charging pad used to charge devices with the Qi standard]] thumb|Electric vehicle wireless charging station

===Electronics=== The most commercially-successful standard for compatibility between inductive chargers and small electronic devices is the Qi standard, which started development in 2008 and was first published in 2010. Qi quickly expanded in the mid 2010s,<ref>{{citation |url=https://hub.hku.hk/bitstream/10722/247386/1/content.pdf |author=S.Y. Ron Hui |title=Past, Present and Future Trends of Non-Radiative Wireless Power Transfer |journal=CPSS Transactions on Power Electronics and Applications |year=2016}}</ref> and after a period of having three competing standards<ref name="edn-2019" /> Qi became ubiquitous by the mid 2020s.<ref>{{citation |url=https://www.wired.com/story/what-is-qi2-wireless-charging/ |title=What Is Qi2? The Wireless Charging Standard Goes Magnetic |website=WIRED |author=Simon Hill |date=August 21, 2025}}</ref> Other standards include: Power Matters Alliance (PMA), which was publicly announced in January 2012;<ref>{{cite web |url=http://standards.ieee.org/news/2012/pma.html |title=Global Industry Leaders Aim To Refine Power in 21st Century as Smart and Wireless with Formation of the Power Matters Alliance |publisher=IEEE newsroom |date=2012-01-09 |url-status=dead |archive-url=https://web.archive.org/web/20130713114044/http://standards.ieee.org/news/2012/pma.html |archive-date=2013-07-13 }}</ref> and Rezence, which was developed by the Alliance for Wireless Power (A4WP) and merged with PMA in 2015 under the AirFuel name.<ref>{{cite web |url=https://www.airfuel.org/2015/11/03/verge-former-wireless-charging-rivals-join-forces-new-airfuel-alliance/ |title=Former wireless charging rivals join forces as new AirFuel Alliance |publisher=airfuel.org |date=2015-11-03 |access-date=2019-06-08 |archive-date=2019-06-08 |archive-url=https://web.archive.org/web/20190608175905/https://www.airfuel.org/2015/11/03/verge-former-wireless-charging-rivals-join-forces-new-airfuel-alliance/ |url-status=dead }}</ref>

===Electric vehicles=== A group was launched in May 2010 by the Consumer Electronics Association to set a baseline for interoperability for chargers. General Motors, Toyota, and Ford expressed interest in the technology and the standards effort.<ref>{{cite web |url=http://www.eetimes.com/electronics-news/4209856/Car-makers-signal-interest-in-wireless-charging |last=Merritt |first=Rick |title=Car makers signal interest in wireless charging |work=EE Times |date=October 20, 2010 |url-status=live |archive-url=https://web.archive.org/web/20101028125931/http://www.eetimes.com/electronics-news/4209856/Car-makers-signal-interest-in-wireless-charging |archive-date=October 28, 2010 }}</ref> Daimler's Head of Future Mobility, Professor Herbert Kohler, expressed caution and said in 2011 that the inductive charging for EVs was at least 15 years away, and the safety aspects of inductive charging for EVs have yet to be looked into in greater detail.<ref>{{cite journal |last=Davis |first=Matt |title=Mission Critical |journal=Electric & Hybrid, Vehicle Technology International |date=July 2011 |pages=68}}</ref>

The first standard for vehicle wireless charging was the SAE J2954 standard. It allows inductive car charging over a pad, with power delivery up to 11&nbsp;kW. The standard provides a methodology for activating the charger only when sufficient alignment is detected.<ref>{{cite web |website=SAE International |url=https://www.sae.org/standards/content/j2954/ |title=Wireless Power Transfer for Light-Duty Plug-in/Electric Vehicles and Alignment Methodology |date=23 April 2019}}</ref> As of 2024, standards for higher-power wireless charging and for charging while driving are being developed.<ref name="SAE-DWPT-standards" /> Magne Charge, a largely obsolete inductive charging system, also known as J1773, used to charge battery electric vehicles (BEV) formerly made by General Motors.

====DWPT EV standards==== {{see also|Electric road#Wireless electric roads}} In the 2020s, organizations continued developing dynamic wireless power transfer (DWPT) electric vehicle (EV) charging technologies and standards. Among them: Vedecom,<ref>{{citation |url=https://www.vedecom.fr/inductive-charging-for-electric-vehicles-while-driving/?lang=en |title=Inductive charging for electric vehicles while driving: a major ecological challenge |date=April 19, 2022 |website=vedecom.fr}}</ref> ENRX (formerly IPT),<ref name="Reilly2024">{{citation |url=https://www.youtube.com/watch?v=hnlukyi9qw0 |contribution=Dynamic Wireless Power Transfer Pilot Projects |author=Greg Reilly|title=Fall 2024 Kent Seminar Series |date=November 21, 2024}}</ref> Magment,<ref>{{citation |url=https://www.concretepavements.org/2021/08/29/german-co-works-alongside-indot-to-create-concrete-roads-that-can-charge-evs-as-they-drive-along/ |title=German Co. Works Alongside INDOT to Create Concrete Roads that Can Charge EVs as they Drive Along |author=Amy M. Dean |work=International Society for Concrete Pavements |date=August 29, 2021 }}</ref> Electreon, Utah State University, Purdue University, and the University of Auckland.<ref>{{citation |url=https://web.archive.org/web/20240606082707if_/https://www.utah.gov/pmn/files/1116757.pdf |title=ASPIRE Steering Committee Mtg, Utah Intelligent Electrified Transportation Planning Initiative |date=April 8, 2024 |website=Utah Department of Transportation}}</ref> WiPowerOne (an offshoot of the KAIST OLEV project) and Electreon, two wireless electric road companies, have been working on new dynamic inductive charging standards in the early 2020s.<ref>{{citation |url=https://www.youtube.com/watch?v=I5xdJMoz_WA |title=Electric Road Systems - PIARC Online Discussion - 17 February 2021 |date=23 February 2021 |at=2 hours and 17 minutes into the video}}</ref> IPT (which later became a subsidiary of ENRX<ref name="IPT-to-ENRX">{{citation |url=https://arendalsfossekompani.no/en/news/enrx-a-new-powerhouse-in-advanced-induction-technology |title=ENRX: A new powerhouse in advanced induction technology |author=ENRX |date=Mar 27, 2023}}</ref>) has been working on its PRIMOVE system that uses inductive cables instead of coils, as according to their CEO the existing standards which use coils are "extremely expensive" for dynamic charging.<ref>{{citation |url=https://www.emobility-engineering.com/wireless-charging/ |title=Wireless Charging |date=September 6, 2021 |author=E-Mobility Engineering staff}}</ref> SAE International has started developing standards for dynamic wireless power transfer in 2023.<ref name="SAE-DWPT-standards" /> The Michigan Department of Transportation (MDOT) has tested one wireless electric road technology from 2023 to 2025 on a quarter-mile stretch of public road. One of the project's goals is developing an interoperable system that will interact with the infrastructure regardless of manufacturer.<ref>{{citation |url=https://www.asce.org/publications-and-news/civil-engineering-source/article/2025/02/05/looking-for-anxiety-free-ev-driving-in-road-charging-holds-promise |title=Looking for anxiety-free EV driving? In-road charging holds promise |author=Robert L. Reid |date=February 5, 2025 |website=ASCE}}</ref>

== Electronic devices == [[File:Smartwatch & Smartphone.jpg|thumb|Samsung Galaxy Z smartphones inductively charging smart watches]] Manufacturers of smartphones have started adding inductive charging technology into their devices in the late 2010s, the majority adopting the Qi wireless charging standard.<ref>{{Cite news|title=Apple buoys wireless charging industry with WPC membership|last=Alleven|first=M|date=2017|work=FierceWirelessTech|id = {{ProQuest|1880513128}}}}</ref> Some battery-powered devices offer wireless bidirectional charging, allowing a charged device to charge the battery of another device.<ref>{{cite web | title=Which Electric Cars Have Bidirectional Charging (V2L, V2G, V2H)? | publisher=Zecar | date=21 March 2025 | url=https://zecar.com/resources/which-electric-cars-have-bidirectional-charging}}</ref><ref>{{cite web | last=Younker | first=Scott | title=iPhone 17 Pro rumor says Apple will finally steal this feature from Samsung Galaxy phones | website=Tom's Guide | date=20 February 2025 | url=https://www.tomsguide.com/phones/iphones/iphone-17-pro-rumor-says-apple-will-finally-steal-this-feature-from-samsung-galaxy-phones}}</ref><ref>{{Cite web |last=Pocket-lint |date=2021-07-30 |title=What is reverse wireless charging? |url=https://www.pocket-lint.com/phones/news/146874-reverse-wireless-charging-explained-which-phones |access-date=2022-04-21 |website=www.pocket-lint.com |language=en-gb}}</ref>

===Early modern proprietary implementations=== {{see also|Wireless power transfer#Inductive coupling}} * Electric toothbrushes which use inductive charging have been commercially available since as early as the 1970s.<ref name="1970s">{{citation |title=Handbook of Small Appliance Troubleshooting and Repair |author=David L. Heiserman |year=1974 |isbn=9780133817492 |pp=182 |publisher=Prentice-Hall}}</ref> * Visteon introduced in 2007 a device inductive charging system to allow vehicles to charge specially made cell phones and MP3 players with compatible receivers.<ref>{{cite web |url = http://www.mobilemag.com/2007/01/03/visteon-to-unveil-wireless-charger-for-your-car-at-ces/ |title = Visteon to unveil wireless charger for your car at CES |date = 2007-01-03 |publisher = mobilemag.com |url-status = live |archive-url = https://web.archive.org/web/20130606095001/http://www.mobilemag.com/2007/01/03/visteon-to-unveil-wireless-charger-for-your-car-at-ces/ |archive-date = 2013-06-06 }}</ref> * Energizer introduced in 2009 an inductive charging station for the Wii remote.<ref>{{cite web |url = http://gear.ign.com/articles/977/977418p1.html |title = Energizer Induction Charger for Wii Preview |date = 2009-04-28 |publisher = IGN.com |url-status = live |archive-url = https://web.archive.org/web/20090502172350/http://gear.ign.com/articles/977/977418p1.html |archive-date = 2009-05-02 }}</ref> * The 2009 Palm Pre smartphone had an optional inductive charger accessory, the "Touchstone". Further Palm and HP devices used Touchstone charging technology.<ref>{{cite web |first = Paul |last = Miller |url = https://www.engadget.com/2009/01/08/palm-pres-wireless-charger |title = Palm Pre's wireless charger, the Touchstone |date = 2009-01-08 |publisher = Engadget |url-status = live |archive-url = https://web.archive.org/web/20170912222440/https://www.engadget.com/2009/01/08/palm-pres-wireless-charger/ |archive-date = 2017-09-12 }}</ref><ref name=digitaltrends100225>{{cite web |first = Nick |last = Mokey |url = http://www.digitaltrends.com/product-reviews/cell-phone-reviews/cell-phone-smart-phone-reviews/palm-pre-plus-review/ |title = Palm Pre Plus Review |publisher = Digital Trends |date = February 25, 2010 |access-date = 2010-03-09 |url-status = live |archive-url = https://web.archive.org/web/20100324155310/http://www.digitaltrends.com/product-reviews/cell-phone-reviews/cell-phone-smart-phone-reviews/palm-pre-plus-review/ |archive-date = March 24, 2010 }}</ref> * An MIT inductive power project started in 2006, WiTricity, uses a curved coil and capacitive plates.<ref>{{cite web |last = Hadley |first = Franklin |url = http://web.mit.edu/newsoffice/2007/wireless-0607.html |title = Goodbye wires… |work = MIT News |publisher = Massachusetts Institute of Technology |date = 2007-06-07 |access-date = 2007-08-23 |url-status = live |archive-url = https://web.archive.org/web/20070903142421/http://web.mit.edu/newsoffice/2007/wireless-0607.html |archive-date = 2007-09-03 }}</ref><ref>{{cite journal | last = Castelvecchi | first = Davide | url = http://web.mit.edu/newsoffice/2006/techtalk51-9.pdf | title = Wireless energy may power electronics: Dead cell phone inspired research innovation | journal = TechTalk | publisher = Massachusetts Institute of Technology | volume = 51 | issue = 9 | date = November 15, 2006 | access-date = August 23, 2007 | url-status = live | archive-url = https://web.archive.org/web/20070302091819/http://web.mit.edu/newsoffice/2006/techtalk51-9.pdf | archive-date = March 2, 2007 }}</ref>

==Transportation== [[File:Движущиеся автомобили на макете.jpg|thumb|A wirelessly powered model lorry at the Grand Maket Rossiya museum]] Electric vehicle wireless power transfer or wireless charging is generally divided into three categories: stationary charging when the vehicle is parked for an extended period of time; dynamic charging when the vehicle is driven on roads or highways; and quasi-dynamic or semi-dynamic charging, when the vehicle moves at low speeds between stops,<ref name="Jang2018"/>{{Rp|847}} for example when a taxi slowly drives at a taxi rank.<ref>{{citation |url=https://www.autofutures.tv/2021/09/10/sprint-power-mobility-moments/ |title=Tomorrow's Wireless Charging Taxis – Mobility Moments With Sprint Power Director Ben Russell |author=Tom Fogden |date=September 10, 2021 |website=autofutures.tv |access-date=April 3, 2022 |archive-date=October 18, 2021 |archive-url=https://web.archive.org/web/20211018070507/https://www.autofutures.tv/2021/09/10/sprint-power-mobility-moments/ |url-status=dead }}</ref>

Inductive charging is not considered a mature dynamic charging technology as it delivers the least power of the three electric road technologies, its receivers lose 20%-25% of the supplied power when installed on trucks, and its health effects have yet to be documented, according to a French government working group on electric roads.<ref>{{citation |url=https://www.lemoniteur.fr/article/mobilite-electrique-2-5-une-fenetre-etroite-pour-brancher-les-autoroutes.2203237 |title=Sur les routes de la mobilité électrique |author=Laurent Miguet |date=April 28, 2022 |website=Le Moniteur}}</ref> Similarly, research in Germany by BASt in 2025 estimated 76%–81% overall efficiency for heavy goods transport.<ref>{{citation |author=F. Otto|contribution=ERS With Wireless Charging Through the Use of Precast Concrete Elements – Design Aspects and Demonstration |year=2026 |display-authors=etal |title=17th World Congress on Road Winter Service, Resilience and Decarbonization |publisher=PIARC |url=https://pre-proceedings-chambery2026.piarc.org/ressources/files/source/2/13d10fe8-IP0226-Otto-E.pdf}}</ref> Trials in Norway in 2025 found that coil misalignment of more than {{cvt|3|cm|in}} can severely lower power transfer.<ref name="Norway-2025" /> SAE International notes that wireless charging systems do not have well-established foreign object detection technologies, and proposes establishing safety tests for these technologies. Foreign objects pose a fire or burn risk if metals or organisms are between the ground pad and the receiver when the system is active.<ref name="SAE-DWPT-standards">{{citation|publisher=US Department of Transportation Federal Transit Administration|date=December 2024|title=Effectiveness of Wireless Charging for Electric Transit Buses|author=Katrina Sutton|url=https://www.transit.dot.gov/sites/fta.dot.gov/files/2024-12/FTA-Report-No-0270.pdf|website=FTA Reports and Publications |pages=10–13}}</ref>

===Early developments=== M. Hutin and M. Le-Blanc proposed in 1894 an apparatus and method to power an electric vehicle with inductive power transfer.<ref name="HutinPatent" /> At the time, combustion engines proved more popular, and this technology was not widely implemented.<ref name="Treffers" /> In 1972, Professor Don Otto of the University of Auckland proposed a vehicle powered by induction using transmitters in the road and a receiver on the vehicle.<ref name="Treffers" /> Bolger, Kirsten, and Ng implemented in 1978 an electric vehicle powered by inductive power transfer at a frequency of 180&nbsp;Hz and power of 20&nbsp;kW.<ref name="Treffers" /> An inductive-charging bus was operated in the 1980s in California, and similar developments in inductive power transfer were being explored in France, Germany, and other European countries.<ref name="Treffers" />

===Early modern examples=== [[File:Primove Charging Pad1 Markuskirche Mannheim Germany.jpg|thumb|200kW Charging-Pad for Buses, 2020 Bombardier Transportation]] *In 1997 Conductix-Wampfler started testing wireless charging in Germany. In 2002 the technology was implemented in 20 buses in operation in Turin, Italy. In 2008 the technology was implemented in a Mercedes-Benz A-Class E-CELL.<ref name="Conductix-1997">{{citation |url=https://roogle2.region-stuttgart.de/wp-content/uploads/2013/11/publikationen_Elektromobilitaet_Kompetenzatlas.pdf |page=44 |title=Charge and go! |author=Mathias Wechlin |publisher=e-mobil BW |year=2013}}</ref><ref>{{cite web |url = https://lup.lub.lu.se/search/files/37941174/elektrifering_av_stadsbussar_k2_wp_2016_12.pdf |pp=40–44 |title =Elektrifiering av stadsbussar: En genomgång av erfarenheter i Sverige och Europa |author=Malin Aldenius |display-authors=etal |publisher=K2 - Nationellt kunskapscentrum för kollektivtrafik |year = 2016}}</ref> With the participation of the local municipality and several businesses, field trials were begun in March 2010. The first system was sold to Google in 2011 for employee use at the Mountain View campus.<ref>{{cite web |last=Thibaut |first=Kyle |title=Google Is Hooking Up Their Employees With Plugless Power For Their Electric Cars (Video) |url=https://techcrunch.com/2011/03/22/google-is-trying-out-plugless-power-for-their-electric-cars-video/ |website=TechCrunch.com |date=22 March 2011 |publisher=Techcrunch |access-date=March 6, 2015 |url-status=live |archive-url=https://web.archive.org/web/20150402131414/http://techcrunch.com/2011/03/22/google-is-trying-out-plugless-power-for-their-electric-cars-video/ |archive-date=April 2, 2015 }}</ref> * Magne Charge inductive charging was employed by several types of electric vehicles around 1998, but was discontinued<ref>{{cite web |url=http://www.eanet.com/ev1-club/ |title=EV1 Club Home Page |quote=GM Pulls the Plug on Inductive Charging: Letter from General Motors Advanced Technology Vehicles (Letter dated 2002-03-15) |publisher=EV1 Club |access-date=2007-08-23 |url-status=live |archive-url=https://web.archive.org/web/20080603161730/http://www.eanet.com/ev1-club/ |archive-date=2008-06-03 }}</ref> after the California Air Resources Board selected the SAE J1772-2001, or "Avcon", conductive charging interface<ref>{{cite web |url=http://www.arb.ca.gov/regact/charger/uid.pdf |title=Rulemaking: 2001-06-26 Updated and Informative Digest ZEV Infrastructure and Standardization |date=2002-05-13 |work=title 13, California Code of Regulations |publisher=California Air Resources Board |access-date=2010-05-23 |quote=Standardization of Charging Systems |url-status=live |archive-url=https://web.archive.org/web/20100615234417/http://www.arb.ca.gov/regact/charger/uid.pdf |archive-date=2010-06-15 }}</ref> for electric vehicles in California in June 2001.<ref>{{cite press release |title=ARB Amends ZEV Rule: Standardizes Chargers & Addresses Automaker Mergers |url=http://www.arb.ca.gov/newsrel/nr062801.htm |publisher=California Air Resources Board |date=2001-06-28 |access-date=2010-05-23 |quote=the ARB approved the staff proposal to select the conductive charging system used by Ford, Honda and several other manufacturers |url-status=dead |archive-url=https://web.archive.org/web/20100616001956/http://www.arb.ca.gov/newsrel/nr062801.htm |archive-date=2010-06-16 }}</ref> General Motors and Toyota agreed on this interface and it was also used in the Chevrolet S-10 EV and Toyota RAV4 EV vehicles. * EPCOT Universe of Energy is equipped with moving theater "pews," which take passengers/viewers through the exhibit. They are self-propelled, and inductively recharged when at rest.<ref>{{Cite web |title=EPCOT's Universe of Energy Companion Site: Pavilion |url=https://progresscityusa.com/energy/tech_charging.htm |access-date=2022-04-22 |website=progresscityusa.com}}</ref> This exhibit with the recharging technology was in place ca. 2003. * In November 2011, the Mayor of London, Boris Johnson, and Qualcomm announced a trial of 13 wireless charging points and 50 EVs in the Shoreditch area of London's Tech City, due to be rolled out in early 2012.<ref>{{cite web |url= https://www.sourcelondon.net/london-charges-ahead-wireless-electric-vehicle-technology |title=London charges ahead with wireless electric vehicle technology |publisher=Source London, Transport for London |date=November 10, 2011 |access-date=2011-11-11 |url-status=dead |archive-url= https://web.archive.org/web/20120424030306/https://www.sourcelondon.net/london-charges-ahead-wireless-electric-vehicle-technology |archive-date=24 April 2012 }}</ref><ref>{{cite web |url= https://www.qualcomm.com/news/releases/2011/11/10/first-electric-vehicle-wireless-charging-trial-announced-london |title=First Electric Vehicle Wireless Charging Trial Announced for London |publisher=Qualcomm Incorporated |date=November 10, 2011 |access-date=2011-11-11}}</ref> In October 2014, the University of Utah in Salt Lake City, Utah added an electric bus to its mass transit fleet that uses an induction plate at the end of its route to recharge.<ref>{{cite news |last=Knox |first=Annie |title=University of Utah electric bus runs on a wireless charge |url=http://www.sltrib.com/home/1754251-155/bus-battery-wave-lake-salt-vehicles |newspaper=Salt Lake Tribune |access-date=December 17, 2016 |url-status=live |archive-url=https://web.archive.org/web/20161220170345/http://www.sltrib.com/home/1754251-155/bus-battery-wave-lake-salt-vehicles |archive-date=December 20, 2016 }}</ref> UTA, the regional public transportation agency, planned to introduce similar buses in 2018.<ref>{{cite web |title=UTA Announces Plans to Add First All-Electric Buses to Fleet |url=https://www.rideuta.com/news/2016/04/UTA-Announces-Plans-for-All-Electric-Buses |website=Ride UTA |publisher=Utah Transit Authority |access-date=17 December 2016 |url-status=live |archive-url=https://web.archive.org/web/20161220130127/https://www.rideuta.com/news/2016/04/UTA-Announces-Plans-for-All-Electric-Buses |archive-date=20 December 2016 }}</ref> In November 2012 wireless charging was introduced with 3 buses in Utrecht, The Netherlands. January 2015, eight electric buses were introduced to Milton Keynes, England, which uses inductive charging in the road with IPT technology at either end of the journey to prolong overnight charges.<ref>{{cite web |url=https://www.bbc.co.uk/news/technology-25621426 |title=Wirelessly charged electric buses set for Milton Keynes |publisher=BBC |date=January 9, 2015 |access-date=2015-01-08 |url-status=live |archive-url=https://web.archive.org/web/20150114052059/http://www.bbc.co.uk/news/technology-25621426 |archive-date=January 14, 2015 }}</ref> *Bombardier-Transportation presented in September 2015 its PRIMOVE 3.6&nbsp;kW Charger for cars,<ref>{{cite web | url = http://primove.bombardier.com/media/news/news-detail-page/article////experts-convinced-by-primove-solution-for-cars.html | title = Experts convinced by PRIMOVE solution for cars | publisher = Bombardier | author = Bombardier Mannheim | date = 2015-09-17 | access-date = 2015-09-17 | url-status = dead | archive-url = https://web.archive.org/web/20160405182716/http://primove.bombardier.com/media/news/news-detail-page/article////experts-convinced-by-primove-solution-for-cars.html | archive-date = 2016-04-05 }}</ref> which was developed at Site in Mannheim, Germany.<ref>{{cite web | url = http://de.bombardier.com/content/dam/Websites/bombardiercom/Sites/supporting-documents/BT-SiteFactSheet-Mannheim-Germany-2014-DE.pdf | title = SITE FACT SHEET Mannheim Germany | publisher = Bombardier | author = Sybille Maas-Müller | date = 2015-03-12 | access-date = 2015-03-12 | url-status = dead | archive-url = https://web.archive.org/web/20160405182720/http://de.bombardier.com/content/dam/Websites/bombardiercom/Sites/supporting-documents/BT-SiteFactSheet-Mannheim-Germany-2014-DE.pdf | archive-date = 2016-04-05 }}</ref> Primove was bought in 2021 by IPT,<ref>{{citation |url=https://www.youtube.com/watch?v=KGseqj4h8Zk |title= IPT - 25 years in 2 minutes |author=IPT Technology ENRX |website=YouTube |date=May 20, 2022}}</ref> which by 2023 became a subsidiary of ENRX.<ref name="IPT-to-ENRX" /> *Transport for London trialed inductive charging for double-decker buses in London in 2014.<ref>{{cite web|title=New hybrid bus charging technology trial announced|url=https://tfl.gov.uk/info-for/media/press-releases/2014/august/new-hybrid-bus-charging-technology-trial-announced|website=Transport for London|access-date=2 December 2016|url-status=live|archive-url=https://web.archive.org/web/20160824211611/https://tfl.gov.uk/info-for/media/press-releases/2014/august/new-hybrid-bus-charging-technology-trial-announced|archive-date=24 August 2016}}</ref> *Evatran began selling the Plugless L2 Wireless charging system to the public in 2014.<ref>{{cite news |last=Bacque |first=Peter |title=Evatran to begin shipping its Plugless electric vehicle charging system |url= http://www.richmond.com/business/national-international/article_e92e9d29-28f4-523f-b782-22f137b2a540.html |access-date=March 6, 2015 |publisher=Richmond.com |date=January 6, 2014}}</ref> * Wärtsilä operated a full-scale pilot installation in 2017 employing 1.6MW of power over {{cvt|50|cm|in}} distance between landside and onboard coils for charging of an electric hybrid ferry in commercial operation. The pilot test was run for one year.<ref>{{cite web | url=https://www.wartsila.com/media/videos?wchannelid=s8uxmc66ya&wmediaid=yrl0nc9sww | title=Videos - Wärtsilä }}</ref> *{{Anchor|Momentum Dynamics|InductEV}}A partnership between Cabonline, Jaguar, Momentum Dynamics, and Fortum Recharge is trialed wireless charging a taxi fleet in Oslo, Norway. The fleet consisted of 25 Jaguar I-Pace SUVs equipped with inductive charging pads rated at 50-75&nbsp;kW. The pads use resonant inductive coupling operating at 85&nbsp;Hz.<ref>{{Cite web|title=Wireless Charging Tech to Keep EVs on the Go|url=https://spectrum.ieee.org/wireless-charging-tech-to-keep-evs-on-the-go|access-date=2020-09-29|website=IEEE Spectrum: Technology, Engineering, and Science News|date=27 August 2020|language=en}}</ref> Momentum Dynamics, which was renamed InductEV,<ref>{{citation |url=https://www.bizjournals.com/philadelphia/news/2025/11/28/inductev-electreon-electric-vehicles.html |title=King of Prussia's InductEV to be acquired by Israeli firm for $10.5M |author=Ryan Mulligan |website=Philadelphia Business Journal |date=November 28, 2025}}</ref> has entered insolvency assignment in August 2025.<ref>{{citation |url=https://www.law.com/radar/card/de-na-559908-inductev-inc-v-inductev-abc-llc |title=Inductev Inc v. Inductev ABC LLC |website=Law.com |date=August 27, 2025}}</ref>

===Dynamic charging=== Wireless charging of an electric vehicle while driving is known as "dynamic wireless charging" or "dynamic wireless power transfer", DWPT. The first working full-scale DWPT prototype is generally regarded to have been developed at the University of California, Berkeley in the 1980s and 1990s. The first commercialized DWPT system, Online Electric Vehicle (OLEV), was developed as early as 2009 by researchers at the KAIST.<ref name="Jang2018">{{citation |url=https://koasas.kaist.ac.kr/handle/10203/246539 |title=Survey of the operation and system study on wireless charging electric vehicle systems |journal=Transportation Research Part C |year=2018 |issue=95 |author=Young Jae Jang|volume=95 |pages=844–866 |doi=10.1016/j.trc.2018.04.006 |bibcode=2018TRPC...95..844J |doi-access=free }}</ref>{{Rp|848}} Vehicles using the system draw power from a power source underneath the road surface, which is an array of inductive rails or coils.<ref>{{cite news |url=http://newatlas.com/kaist-olev-electric-vehicle/12557/ |last=Ridden |first=Paul |title=Korean electric vehicle solution |work=New Atlas |date=August 20, 2009 |url-status=live |archive-url=https://web.archive.org/web/20170405171420/http://newatlas.com/kaist-olev-electric-vehicle/12557/ |archive-date=April 5, 2017 }}</ref><ref>H. Feng, R. Tavakoli, O. C. Onar and Z. Pantic, "Advances in High-Power Wireless Charging Systems: Overview and Design Considerations," in IEEE Transactions on Transportation Electrification, vol. 6, no. 3, pp. 886-919, Sept. 2020, {{doi|10.1109/TTE.2020.3012543}}.</ref> Commercialization efforts of the technology have not been successful because of high costs.<ref>{{cite news|url=https://www.koreatimes.co.kr/www/tech/2019/04/325_265924.html|title=ICT minister nominee accused of wasting research money|author=Kwak Yeon-soo|date=March 24, 2019|newspaper=The Korea Times}}</ref>

The main technical challenge of DWPT is low efficiency,<ref name="RISE2021" />{{Rp|57}} and implementation has not been widespread as of 2025 due to high costs.<ref>{{citation |url=https://www.youtube.com/watch?v=-jgjuSwbW2E&t=2m38s |title= Charge as you drive: France trials motorway that powers EVs on the go |publisher=Channel NewsAsia |date=November 18, 2025}}</ref> The cost of a single wireless electric lane at 50% coverage at large-scale deployment was estimated in 2021 to be about 6.5 million dollars per mile.<ref>{{citation |author=Konstantinou, T. |display-authors=etal |year=2021 |title=Feasibility study and design of in-road electric vehicle charging technologies |publisher=Purdue University |doi=10.5703/1288284317353|doi-access=free }}</ref>

The German Ministry of Economy, BMWK tested in-road wireless EV charging infrastructure implemented by Electreon in 2023. The tests included a bus equipped with inductive coils that receive power from a 200-meter strip of transmitters under the road surface. The receivers were able to collect 64.3% of the energy emitted from the transmitters. Installation proved complex and costly, and finding suitable locations for the coils' roadside power cabinets proved difficult.<ref name="WPTCE-japan-2024">A. Wendt et al., "Wireless Electric Road Systems – Technology Readiness and Recent Developments," 2024 IEEE Wireless Power Technology Conference and Expo (WPTCE), Kyoto, Japan, 2024, pp. 177-182, doi: 10.1109/WPTCE59894.2024.10557264.</ref>

===Effects on road surface=== Inductive charging infrastructure was found in 2017 to increase the occurrence of reflective cracks in road surfaces.<ref name="RISE2021">{{citation |url=https://ri.diva-portal.org/smash/get/diva2:1534916/FULLTEXT02.pdf |title=Research & Innovation Platform for Electric Road Systems |author=Martin G. H. Gustavsson |publisher=RISE |isbn=978-91-89385-08-5 |date=March 5, 2021 }}</ref>{{Rp|64}}<ref>F. Chen, N. Taylor, R. Balieu, and N. Kringos, “Dynamic application of the Inductive Power Transfer (IPT) systems in an electrified road: Dielectric power loss due to pavement materials,” Construction and Building Materials, vol. 147, pp. 9–16, Aug. 2017, doi: 10.1016/j.conbuildmat.2017.04.149</ref> Testing of various bonding materials between the inductive coils and the asphalt in 2023 at Nantes showed that standard installation techniques of inductive coils under the asphalt were not satisfactory and resulted in critical strains. Performance was satisfactory with the use of specific bonding resins, with non-critical degradation in performance compared to reference pavements with no inductive coils. Despite satisfactory results, even the best-performing methods showed risk of debonding of the casing of the coils from the top layer of the road.<ref>{{citation |url=https://www.youtube.com/watch?v=QZtLOuZ0Xmk&t=42m50s |contribution=Advancing road-based charging for electric vehicles |author=Pierre Hornych|title=Fall 2024 Kent Seminar Series|date=October 11, 2024}}{{br}}{{citation |url=http://pavetrack.com/APT/2025/2025.06%20-%20IFSTTAR.pdf |title=Evaluation of Electric Road Systems using APT tests |author=Pierre Hornych |date=June 20, 2025}}</ref> ÉTS and Université Laval studied the structural performance of in-pavement inductive coils in 2025, similarly finding evidence of debonding.<ref>{{citation |url=https://www.tandfonline.com/doi/abs/10.1080/14680629.2025.2492142 |title=Evaluating the structural performance of eRoad pavements: impact of inductive charging coils on mechanical behaviour |author=Danial Arzjania |display-authors=etal|date=May 4, 2025 |journal=Road Materials and Pavement Design |volume=26 |pages=55–71 |doi=10.1080/14680629.2025.2492142|url-access=subscription }}</ref><ref>{{citation |contribution=Structural Performance of Electric Road Pavement structures with embedded Inductive Charging Coils using Heavy vehicle simulator |author=Danial Arzjania |year=2026 |display-authors=etal |title=17th World Congress on Road Winter Service, Resilience and Decarbonization |publisher=PIARC}}</ref> The 2023 Nantes trials showed increased risk of thermal damage to the road under regular operating conditions due to the induction coils exceeding temperatures of {{convert|100|C|0}}.<ref name="Hornych-AIPCR-2023">{{Citation| last = Hornych | first = Pierre| contribution = Design of a pavement solution for electric vehicle charging by induction| year = 2023| title = XXVIIe Congrès mondial de la Route| publisher = AIPCR| contribution-url = https://hal.science/hal-04420080}}</ref> INDOT has been testing in 2024 a DWPT installation with special polymer-concrete previously used for bridges.<ref name="Reilly2024"/>{{Rp|at=38m19s}}

== Medical implications == {{refimprove|section|date=January 2026}} Wireless charging is making an impact in the medical sector by means of being able to charge implants and sensors long-term that is located beneath the skin. Multiple companies offer rechargeable medical implant (e.g. implantable neurostimulators) which use inductive charging. Researchers have been able to print wireless power transmitting antenna on flexible materials that could be placed under the skin of patients. This could mean that under skin devices that could monitor the patient status could have a longer-term life and provide long observation or monitoring periods that could lead to better diagnosis from doctors. These devices may also make charging devices like pacemakers easier on the patient rather than having an exposed portion of the device pushing through the skin to allow corded charging. This technology would allow a completely implanted device making it safer for the patient. It is unclear if this technology will be approved for use – more research is needed on the safety of these devices. While these flexible polymers are safer than ridged sets of diodes they can be more susceptible to tearing during either placement or removal due to the fragile nature of the antenna that is printed on the plastic material. While these medical based applications seem very specific the high-speed power transfer that is achieved with these flexible antennas is being looked at for larger broader applications.<ref>{{Cite journal|last1=Yong Zhi|first1=Cheng|last2=Ji|first2=Jin|last3=Wen Long|first3=Li|last4=Jun Feng|first4=Chen|last5=Bin|first5=Wang|last6=Rong Zhou|first6=Gong|year=2017|title=Indefinite-permeability metamaterial lens with finite size for miniaturized wireless power transfer system |journal=AEU - International Journal of Electronics and Communications|volume=12|pages=1777–1782}}</ref>

==See also== {{div col|colwidth=23em}} * Charging station * Conductive wireless charging * Ground-level power supply * Litz wire * Wardenclyffe Tower * Wireless power transfer * Wireless Power Consortium {{div col end}}

==References== {{Reflist|refs=

<ref name="HutinPatent" > {{cite patent | country = | number = US527857A | status = | title = TRANSFORMER SYSTEM FOR ELECTRIC RAILWAYS | pubdate = 1894-10-23 | gdate = | fdate = | pridate = | inventor = Maurice Hutin and Maurice Leblanc | invent1 = | invent2 = | assign1 = | assign2 = | class = | url = https://patents.google.com/patent/US527857A/en }}</ref>

<ref name="Treffers" >{{Cite magazine |last=Treffers |first=Menno |title=History, Current Status and Future of the Wireless Power Consortium and the Qi Interface Specification |magazine=IEEE Circuits and Systems Magazine |volume=15 |issue=2 |year=2015 |pages=28–31 |doi=10.1109/mcas.2015.2418973 }}</ref>

<ref name="Madzharov et al, 2017" >{{Cite journal |last1=Madzharov |first1=Nikolay D. |first2=Valentin S. |last2=Nemkov |title=Technological inductive power transfer systems |journal=Journal of Electrical Engineering |publisher=The Journal of Slovak University of Technology |volume=68 |issue=3 |pages=235–244 |date=January 2017 |doi=10.1515/jee-2017-0035 |bibcode=2017JEE....68..235M|doi-access=free}}</ref>

}}

{{DEFAULTSORT:Inductive Charging}} Category:Wireless energy transfer