Proterra Catalyst BE35

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Proterra Catalyst BE35
Dallas Area Rapid Transit 45001-a.jpg
Years of manufacture 2016 to present
Length 36 feet
Width 102 inches
Power/Fuel Electricity

The Proterra Catalyst is the company's second generation battery electric low floor transit bus. First launched as a 40-foot bus, the 35-foot Catalyst BE35 was announced in October 2015. Dallas Area Rapid Transit, who has purchased seven buses, was the launch customer.[1] The pilot bus was unveiled at the 2017 American Public Transportation Association Expo and delivered to DART at the start of 2018.[2]

The Catalyst uses a monocoque structure composed of E-glass fibre stitched non-crimp fabric and unidirectional carbon fibre in a vinyl ester resin. It is moulded using the Seeman Composites Resin Infusion Molding Process (SCRIMP), a vacuum-assisted closed infusion molding method, by TPI Composites. A gel-coat layer is first placed in the mould followed by triaxl glass fibre fabic. Unidirectional carbon fibre fabric is used to add strength at key areas. Quadriaxial quasi-isotropic glass fibre fabric is used where strength and stiffness are especially critical. The materials are vacuum bagged and infused with catalyzed vinyl ester resin. The resulting compsoite structure is lightweight and can absorb a large amount of energy in a collision.[3]

The upper body from the roof down to the lower window line, which includes the entire windshield and rear window, is on section. The lower body from the lower window line to the floor is another. The upper section of the roof and the ceiling are glass fibre sandwich structures with a balsa wood core. Components such as doors and interior fittings are attached by either molding stainless steel inserts into the laminate or by bonding.[3]

In a standard fast charge (FC) configuration, the bus can travel up to 55 miles before the lithium–titanate batteries need to be recharged. An extended range (XR) battery option allows the bus to travel up to 235 miles between charges. At the 2016 American Public Transit Association (APTA) Annual Meeting, Proterra unveiled their E2 (Efficient Energy) battery option with a capacity of 440 to 660 kWh that allows the bus to travel up to 251 miles. This range is able to meet a full day's worth of service for some agencies.[4]

At the 2017 American Public Transit Association EXPO in Atlanta, Proterra introduced their DuoPower drivetrain. It integrates two 190 kWh electric motors and two-speed transmission into a planetary axle from AxleTech. It boasts almost twice the horsepower as the standard ProDrive drivetrain and is five times more efficient than a standard diesel bus.[5] With the DuoPower drivetrain, the 35-foot Catalyst E2 has a nominal range of 302 miles.

The bus's batteries can be charged enroute with a proprietary overhead charging station, which features automatic docking.[6] The standard FC option can be fully charged in ten minutes, while the XR option can be fully charged in approximately one hour.[7] The bus can also be plugged in using a J1772 CCS charger at the garage. The E2 is only charged this way while the bus is out of service, typically when it is parked overnight, at the garage and is fully charged in three to four hours.

The 35-foot Catalyst has a slightly different appearance from the 40-foot Catalyst. The headlights have been re-positioned and the windshield has been reshaped. The tail lights are round rather than rectangular.


Length: 36' 11"
Width: 102"
Height: 135.5"
Wheelbase: 20' 3"
GVWR: 38,000 lbs
Curb weight: 25,746 to 29,008 lbs
Traction motor Availability
ProDrive drivetrain UQM HD220 220 kW peak permanent magnet motor 2014 to present
DuoPower drivetrain Dual independent 190 kW motors 2017 to present
Eaton EEV-7202 2-speed auto-shift EV transmission
Independent front suspension and multi-link air-ride rear suspension
Four wheel disc brakes w/ ABS and optional traction control
Battery options
Series Model Nominal range Standard charge time Curb weight
ProDrive FC (Fast Charge) FC 55 miles <1 hour 28,925 lbs
FC+ 72 miles <1 hour 30,500 lbs
DuoPower FC (Fast Charge) FC 67 miles <1 hour 28,925 lbs
FC+ 86 miles <1 hour 30,500 lbs
ProDrive XR (eXtended Range) XR 136 miles <2.5 hours 27,350 lbs
XR+ 193 miles <2.5 hours 28,925 lbs
DuoPower XR (eXtended Range) XR 163 miles <2.5 hours 27,550 lbs
XR+ 235 miles <2.5 hours 28,925 lbs
ProDrive E2 (Efficient Energy) E2 251 miles <3 hours 30,500 lbs
DuoPower E2 (Efficient Energy) E2 302 miles <3 hours 30,500 lbs


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Demonstrator and engineering units

Below is a list of known demonstrator and engineering buses.

Fleet number Thumbnail Year VIN Motors Notes
  • Blue and green wrap
  • Demo with SMART August 21, 2021


  1. Proterra Expands its Catalyst™ EV Bus Platform to Include a Nimbler Bus. Press release. 05 October 2015. Protera, Inc. Retrieved on 16 November 2016.
  2. DART Demos New Proterra Zero-Emission, All-Electric Buses. 10 January 2018.
  3. 3.0 3.1 Dawson, Donna. [ "A clean technology for clean, zero-emissions buses." CompositesWorld, 01 October 2018.
  4. Proterra Catalyst® E2 Series Sets New Industry Precedent with a Nominal Range of up to 350 Miles. Press release. 12 September 2016. Protera, Inc. Retrieved on 16 November 2016.
  5. Proterra Introduces the DuoPower™ Drivetrain for its Catalyst® Zero-Emission Buses at APTA. Press release. 09 October 2017. Proterra.
  6. Proterra, bus maker, aims to follow Tesla model. Retrieved on 02 September 2014.
  7. Proterra Introduces Extended-Range Electric Bus, Flexible Battery System. Press release. 24 February 2016. Protera, Inc. Retrieved on 16 November 2016.