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Proterra boosts capacity of Catalyst XR battery pack 28% to 330 kWh with new design, same volume as predecessor

Battery-electric bus manufacturer Proterra announced a new battery pack design for the Proterra Catalyst XR transit vehicle at the American Public Transportation Association Bus and Paratransit Conference (APTA). Within the same volumetric footprint as that in the original Catalyst XR, the new energy storage system now holds 28% more energy at 330 kWh.

All current Catalyst XR customers that are still waiting on their buses to be delivered will receive a complimentary upgrade to the higher energy level.

Proterra offers both extended-range (XR) and fast-charge (FC) versions of its electric bus, using different battery technologies. (Earlier post.) The TerraVolt FC fast charge battery option (lithium titanate, LTO chemistry) allows for maximum run time with minimum dwell time. The first Catalyst XR Extended Range product uses an NMC higher energy-density pack.

The XR is compatible with the fast charging equipment (although the charge will not be as quick as with the FC); full charge recovery can be accomplished in less than 90 minutes.

In the company’s battery-engineering lab in Silicon Valley, Proterra engineers are designing batteries specifically for heavy-duty EV transit. With extensive background in mechanical, electrical and battery systems engineering, the team architected a new Catalyst XR battery pack for optimal efficiency which now delivers additional range while remaining the lightest vehicle in its class.

Proterra is not yet disclosing changes made to the cells or to the mechanical design of the pack to deliver the boost in capacity within the same volumetric footprint.

Our goal is to enable a complete replacement of fossil-fueled transit vehicles. By steadily improving the range and charging capability of our purpose-built EV transit vehicles, we’re broadening the market for EV transit very quickly, enabling more cities and more routes to go Zero Emission sooner.

—Ryan Popple, CEO of Proterra

The award-winning bus has already achieved the best efficiency rating ever for a 40′ transit bus at 22 MPGe. Nearly six times more efficient than a diesel or CNG bus, the Catalyst is also significantly more energy efficient per mile than the closest competitors’ electric bus.

Other performance benefits of the Catalyst XR2 include:

  • Longest nominal range: capable of traveling a maximum of 194 miles (312 km) on a single charge, based on Altoona efficiency measures. Actual mileage will vary with route conditions.

  • Lightest weight: at least 2,000 lbs. lighter than any other 40’ battery electric bus on the market, while being more efficient.

  • Designed for safety: Catalyst vehicles are purpose-built and engineered for the safest location of batteries—outside of the passenger compartment. The batteries are temperature-controlled and incorporate both active and passive safety systems, with ruggedized, reinforced battery packs that are further separated from passengers by a heavy-duty structural barrier.

EV Simulator. Proterra also has introduced the Proterra EV Simulator. The EV Simulator provides fleet managers with customized, system-level information on electric bus deployment. Designed to visualize mass transit networks and to assess the cost savings, performance improvements and environmental benefits of battery-electric transport, the Proterra EV Simulator generates a side-by-side comparison of Proterra’s transit solutions with diesel, CNG and hybrid technologies on specified transit routes within a chosen public transit system.

Utilizing data that drives Google’s map applications and based on algorithms that are built on performance data from Proterra’s two million miles of real-world experience, the Proterra EV Simulator incorporates a wide variety of variables affecting vehicle performance, including route specifications, local temperatures, passenger load and vehicle efficiency.

The Proterra EV Simulator takes into account energy use of the Proterra electric powertrain and provides an estimated daily route analysis based a specified passenger load, layover times, the number of buses in operation and number of route loops, as well as energy efficiency, vehicle charge time and battery state-of-charge on-route and at the end of the day. Some of the key calculations include:

  • Annual maintenance and operational costs per Proterra bus
  • Lifetime maintenance and fuel savings
  • Overall Total Cost of Ownership (TCO)
  • Energy efficiency MPGe
  • Total daily distance and energy used per day
  • Charge time



This mid-range (194 miles) e-bus performances compare favorably with BYD's and will be able to handle most city routes. Both have almost the same battery and range capacity.

Tripling (3X) the battery capacity, with overnight charging, could make it a decent intercity unit.

The remaining problem to be solved (for the city unit) is the long 90 minutes recharge time with todays limited capacity chargers?

David Freeman

@HarveyD - the article mentions that charging is slower, so the battery chemistry seems to be the limiting factor, not available charge current.

Thus, a 1MWh battery pack would take 90 minutes to charge, even with infinite power.


Yes DF, most of current lithium batteries require 30 to 90 minutes for a quick charge.

Recharging the 1MWh pack required for extended range inter-city e-buses would take a powerful charging facility, at each rest and/or lunch stops + slower overnight charging?

New much higher charge rate battery technologies are being developed and could become available in 5 to 10 years.

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