SAE Sets Charging Standards for Transit Fleets, Other Heavy-Duty EVs

June 02, 2023 by Shannon Cuthrell

A leading standards authority, SAE International, unveils new recommendations for on-route conductive charging of high-weight electric vehicles such as transit buses. 

SAE International (formerly the Society of Automotive Engineers), a Pennsylvania-based mobility standards authority with a member base of over 128,000 engineers and experts, recently outlined a new set of recommendations governing testing and performance requirements for on-route conductive charging systems serving medium- and heavy-duty electric vehicles. 


Nova Bus’s LFSe electric transit model using OPPCharge fast-charging infrastructure

Nova Bus’s LFSe electric transit model using OPPCharge fast-charging infrastructure. Image used courtesy of Nova Bus


The guidelines apply to electric transit buses and other high-capacity applications using conductive automated connection devices (ACDs) that transfer direct current (DC) power. These include infrastructure- and vehicle-mounted pantograph connections, a subset of transit charging marking a shift from traditional plug-in chargers. On-route conductive charging is gaining traction in the medium/heavy-duty EV market, in which reducing downtime is crucial as transportation operators prefer to establish the connection without the driver’s manual input. 

SAE’s new release addresses an area missing from its existing standards that don’t cover on-route conductive charging for the continuous operation of high-capacity EVs like electric transit buses

Mark Kosowski, a document sponsor and technical executive at the Electric Power Research Institute, stated that the recommended practices aim to ensure each connection design is interoperable and safe across different manufacturers.


Updates to J-3105

SAE’s EV charging standard, J-3105, applies to power transfer systems using ACDs. It covers the physical, functional, and electrical testing and performance requirements for conductive power transfer systems, primarily for EVs using an ACD connection capable of transferring DC power, such as battery-electric buses. 

J-3105 was first issued in 2020, but SAE has since updated this framework with two subsections, announced in May. According to SAE, these systems are suitable for power transfer of up to 600 kilowatts with Level 1 charging systems and up to 1.2 megawatts with Level 2 chargers. 

J-3105/1 specifies infrastructure-mounted pantograph (or cross-rail) systems, which are hands-free connections on the infrastructure above the vehicle. The recommendations provide connection interface requirements for EV power transfer systems using conductive ACDs based on a cross-rail design to allow interoperability for on-road vehicles such as buses and coaches. Other configurations could also serve non-standard applications, such as electric mining trucks or port vehicles. 


different types of connectors for heavy-duty conductive automatic charging systems

Types of connectors for heavy-duty conductive automatic charging systems. Image used courtesy of EPRI


J-3105/2 focuses on vehicle-mounted pantograph (bus-up) connection interface requirements for EV power transfer systems using a conductive ACD based on a traditional rail vehicle pantograph design. 

A third document not updated in the latest recommendations, J-31053/3, outlines EV power transfer systems using conductive ACDs based on an enclosed pin and socket design. 


Industry Task Force

The recommendations were developed with the participation of several industry stakeholders, including charging providers, EV manufacturers, and local/regional utilities. Five years ago, SAE formed a task force to explore ACD-related best practices for medium/heavy-duty electric transit vehicles. 


Roof-mounted pantographs

Roof-mounted pantographs provide daytime fast and overnight slow charging for an electric bus fleet in Poland. Image used courtesy of Schunk


The task force included bus manufacturers such as California-based Proterra and Canada’s Nova Bus, charging providers like European tech giants ABB and Siemens, and pantograph and connector manufacturers including Germany-based Schunk and Swiss firms Furrer+Frey and Stäubli. 

A few utilities were also involved, including Southern California Edison and the Sacramento Municipal Utility District, alongside transit fleet transportation authorities from Chicago, Los Angeles, and New York City.