Proterra's high-voltage overhead charging system uses robotic control (and some autonomous software on the bus) to replenish bus batteries in as little as 10 minutes, depending on the size of the battery pack. Charging at 250-1000V (DC) and up to 1400A, the system is eight times faster than the CHAdeMO fast-charging standard and between three and four times faster than Tesla's Superchargers. And unlike the old-fashioned pantograph, which needs to cover the vehicle's entire route, Proterra's system is static. This means bus operators can install them in terminals or at the same locations they use to refill their diesel tanks.
"The interesting thing is these diesel buses have such massive fuel tanks—given how inefficient they are—that it takes longer to completely refill an 80- or 120-gallon diesel bus system than it does to recharge our electric vehicles," explains Proterra CEO Ryan Popple. "So we're actually getting to the point where the vehicles that are configured for fast charge can be replenished faster than you can stick a hose in the side of a diesel bus and fill it with fuel."
According to Popple, Proterra's fast-charger can recharge a 100kWh electric bus in just ten minutes, sufficient for a circulator bus route of 30 (48km) miles or less. That's better than diesel or even natural gas, he told us: "We've gone from something that would have been considered a negative for EVs—slow overnight charging—and now we've gone to the point where EVs are advantaged relative to combustion in terms of speed and ease of refueling." (Recharging the 400kWh batteries of a longer-range electric bus would obviously take longer.)
