Auto Tech

Proterra ushers in a new era of electric transit with 350-mile E2 bus

Electric bus-maker Proterra announces its newest model, the E2, which boasts seating capacity of 40 passengers and a 350-mile range per charge.

One big challenge with electric cars comes from stuffing them full of batteries to give them adequate range, batteries which at the same time increase weight, thus reducing range. That equation changes a bit, however, in the realm of large commercial vehicles where the battery pack makes up a smaller percentage of overall weight, something electric bus-maker Proterra uses to its advantage.

Its latest bus, the E2 Max, not only seats 40 passengers, but also carries a 660-kilowatt-hour battery pack, giving it a range of 350 miles. By contrast, a new variant of the Tesla Model S boasts a 100-kilowatt-hour battery pack, 315 mile range and seats for five adults and two children.

Of course, the demands on public transit are far different than a private vehicle. Proterra's top-of-the-line E2 Max is designed for the longest municipal bus routes. The company's base E2 model, also just announced, comes with a 440-kilowatt-hour battery pack and goes 251 miles on a charge, still far above a typical urban route.

The majority of public transit buses use diesel engines. Along with noise and fumes, these buses emit carbon dioxide, a greenhouse gas contributing to global climate change. Not only do electric buses run more quietly and emission-free, the electricity they use can be generated from a variety of sources, so pricing is not dependent on a single fuel source, in the manner that diesel is tied to the price of oil.

Proterra already manufactures two electric bus models, the FC and XR. The base 36-foot FC model carries a mere 79-kilowatt-hour battery pack, giving it a range of 46 miles. The company was founded in 2004, and sold its first buses in 2009. To date, the company has put 312 electric buses in the hands of municipal, commercial and university transit agencies.

The new E2 bus series use 120-kilowatt chargers, putting maximum recharge time at under five hours. Proterra also makes a rooftop charger available for the E2, so it can take advantage of overhead charging wires on all or part of its route. Overhead charging allows Proterra's buses to run almost continually.