Proterra, a leading manufacturer of all-electric buses, unveiled this week a new battery pack to power its Catalyst XR bus pictured above. The new pack holds 28 percent more energy which adds up to an impressive 330 kWh of energy capacity.

As of March 2016, Proterra had 63 buses on the roads across 10 states. Now the company says that all current Catalyst XR customers will receive a complimentary upgrade with the new battery pack.

Ryan Popple, CEO of Proterra, on the announcement:

“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.”

Proterra is based in South Carolina, but the new battery pack was developed out of the company’s battery-engineering lab in Silicon Valley.

The company’s Chief Technology Officer, Gary Horvat, had a long engineering career at GM and he was involved in several of the automaker’s EV and PHEV programs before joining Fisker Automotive until the company went bankrupt. Horvat on the announcement:

“By increasing the battery’s energy density, the team was able to utilize the Catalyst vehicle’s purpose-built design and maintain its light weight. The improved Catalyst XR marks another step toward Proterra’s goal of providing a high-performance bus that can serve any transit route in the United States.”

Proterra recruited several battery engineering veterans to develop its latest battery pack, including long time Tesla battery engineer, Dustin Grace.

Grace is now heading Proterra’s battery engineering program, but prior to joining the bus maker in September last year, he had an 8-year tenure at Tesla where he was a key team member on several of Tesla’s battery pack programs, including for the 2010 Smart ForTwo EV, 2012 Tesla Model S, 2014 Mercedes-Benz B-Class Electric Drive and more recently the Model 3.

Proterra’s 40’ battery electric bus can travel an impressive 194 miles on a single charge and achieve a best-in-class efficiency rating of 22 MPGe.