The Proterra EcoRide BE35 is a 35 foot (11 m) (nominal length) fast-charge battery electric bus that seats 38 (including the driver) with a total passenger capacity of 60 in its composite low floor body.

[12] This was followed by a 2007 contract for two more fuel cell buses for Burbank, California; by this time the key characteristics were announced: a 35-foot (11 m) composite body provided by Martin Marietta, lithium-titanate batteries, and plug-in charging in addition to onboard charging through the use of a range-extending auxiliary power unit (APU) consisting of two 16 kW fuel cells from Hydrogenics.

[18]: 34  As shown with the fuel cell APU, Proterra claimed the HFC35 had a range of 250 miles (400 km) before needing to be refueled or recharged.

[22][23] The HFC35 prototype exhibited at APTA '08 in San Diego[24] was later demonstrated in Washington, D.C. (Nov 2008)[5] and a nationwide tour in regular service was scheduled for 2009, starting in Columbia, South Carolina[15] as a football stadium shuttle for the University of South Carolina (with maintenance, refueling, and charging at Central Midlands Regional Transit Authority), with Capital Metro in Austin, Texas,[25] and at the 2010 Olympic and Paralympic Winter Games in Vancouver, British Columbia.

[26] The DoD HFC35 was delivered to Joint Base Lewis–McChord in Tacoma, Washington,[27] where it was powered by hydrogen reformed from mewthane produced during wastewater treatment.

[43][44] In June 2016, Proterra announced it would grant royalty-free access to the patents covering their FastFill overhead charging system.

[45] Proterra uses the TerraVolt branding for the battery system and ProDrive for the drivetrain module, which includes the traction motor and optional range-extending APU.

[49] The first HFC35 prototype was not available for service for approximately two months to address a failure in a DC-DC converter, which provided the interface between the fuel cell APU and the traction battery.

[16]: 21 Results from the BE35 STURAA test showed an average, combined fuel economy of 1.81 kWh/mi (1.12 kW⋅h/km) or 20.84 miles per US gallon (11.29 L/100 km) diesel equivalent.