SAE taskforce developing standards for wireless charging for plug-in vehicles; targeting first guideline by end of 2011
|Closed loop wireless charging diagram. Source: Jesse Schneider. Click to enlarge.
SAE has launched a taskforce (SAE J2954) on the “Wireless Charging of Electric and Plug-in Electric Vehicles”—i.e. EVs and PHEVs. The taskforce, which launched in October 2010 and began meeting in November 2010, has a goal of delivering the first SAE guideline by end of 2011 for publishing in 2012. Since additional field data is needed for standardization, said Jesse Schneider of BMW, leader of the J2954 effort, a 2012-13 date is estimated for the balloted standard.
The taskforce goal is to establish performance and safety limits for wireless power transfer for automotive applications while establishing a minimum interoperability requirement. The team is currently reviewing the state of the art of wireless charging (e.g., inductive, magnetic resonance) and compiling an interoperability study.
The scope of the work covers light duty passenger EVs and PHEVs and buses. Charging locations to be considered include residential; on-road (static and dynamic), with Level 1, 2 and 3 capability (the last for buses). Presently the J2954 team is a cross-industry team of auto and bus OEMs, EV infrastructure companies, government laboratories, universities, wireless power and Tier 1 suppliers.
Wireless charging enables electric vehicles to be seemlessly charged without operator interaction. This is an added feature of “refueling” which could be very attractive to EV/PHEV customers, with high efficiencies, basically only having to park in a specific location. Many of the OEMs and EV infrastructure companies have already signed on to J2954. This taskforce is also taking an active role to work from the onset with ISO standards and VDE (German standards) to harmonize this important new trend.—Jesse Schneider, Chair SAE J2954
|Two wireless options
|Inductive charging uses the electromagnetic field to transfer energy between two objects in close proximity.
|A charging station sends energy through inductive coupling to an electrical device, which stores the energy in the batteries.
|Magnetic resonance uses the magnetic coupling of two objects exchanging energy through their varying or oscillating magnetic fields. Resonant coupling occurs when the natural frequencies of the two objects are approx. the same.
Currently, SAE 1773 defines a standard for EV inductive coupled charging. The standard was based upon specific hardware (paddle charger); vehicle-station bidirectional communication was either RF or IrDA. SAE 1772 specifies a conductive charge coupler standard that is not compatible to ISO standard in Europe.
Standard charging could be in the up to ~4 kW range, Schneider says, with more possible for some passenger vehicles and up to 60 kW Level 3 fast charging for some vehicles (e.g., buses). Passenger vehicles could be wirelessly charged during work, parking garage, home use, similar to conductive charging (such as SAE 1772) at a higher power level, with vehicle approval.
This wireless charging effort is different than the conductive plug charging standardization underway in that harmonization is seen as first priority, Schneider said. The SAE J2954 taskforce has established a relationship with ISO/IEC and VDE (German Standard) to ensure open communication to expedite harmonization. VDE is planning to publish their whitepaper on wireless charging for Germany in the first quarter of 2011 and ISO & IEC are planning to standardize in the coming years.
SAE TIR J2954: “Wireless Charging of Electric and Plug-in Hybrid Vehicles” (presentation by Jesse Schneider)