Michael Callender is the director of fleet solutions for
Highland, which offers a subscription-based, turnkey solution to allow school districts to immediately begin implementing electric school buses. In most cases High- land owns the buses and infrastructure, Callender said, and the company also maintains all vechicle charging and maintenance services. “In general, most customers don’t really know what to expect, but they seem relieved that our package includes facilitating training for their mechanics and making sure all their questions and concerns are addressed before the buses ever hit the road,” Callender said. “The most common questions we see are always about safety, for example, is it safe to operate in the rain, can we plug it in during rain or snow, etc., which are answered during training.”
Other Equipment Considerations He also noted that an often overlooked aspect of elec-
tric bus maintenance and repair is the chargers. “Highland spends considerable time and resources testing equipment and improving reliability,” he said. “We actively monitor charging and faults through our charge management software, which enables us to quickly respond to and service any issues. We are learning what is likely to go wrong, with which chargers, and how to quickly respond with solutions (e.g., remote service, hav- ing a bench stock of parts for replacement, etc.).” Electric buses also require new and different mainte- nance because the powertrain systems are different. Electric vehicles, for example, utilize regenerative braking. While an oversimplified analogy, think of an electric motor being operated in reverse. It is using electromagnetic force to apply a braking force, which acts to recapture some of the vehicle’s kinetic energy by charging the battery. However, there are increased torque levels to consider with regenerative braking. Richard Beyer, vice president of technical sales and
vehicle systems at Bendix Commercial Vehicle Sys- tems, said that new braking features include “hill hold,” which prevents the vehicle from rolling backward on an incline or other sloped surfaces. Hill hold supplements automatic transmissions (AT) and automated manual transmissions (AMTs), and makes buses easier to drive, while enabling a more car-like feel for the driver. “Ve- hicles with AT/AMTs are outfitted with these features to provide better control by preventing roll back, especially in hilly areas integrated with surface traffic and stop and go conditions.” When it comes to stopping the vehicle, regenerative braking moves the stopping force that assists braking to the motor. But buses will still have the same brake sys- tems—and most will be the same kind they have always had, either air or hydraulic. Stotler said that Thomas Built Buses chose to use a traditional air or hydraulic braking system to keep con-
30 School Transportation News • AUGUST 2022
First Student technicians complete zero-voltage tests in a Lion Electric Company high-voltage distribution unit, one of many new electric school bus elements that require additional training for maintenance safety and efficiency.
sistency in the shop, as this will provide continuity with the technician’s existing knowledge of braking systems. This will also allow districts to keep up with their current brake and maintenance program. IC Bus is using an air brake system alongside the three
levels of driver-selectable regenerative braking avail- able on the Electric CE Series. The company noted that air brake system service intervals will be significantly extended due to regenerative braking being the primary source of slowing the vehicle down. Using its observa- tions, drivers can use regenerative braking efficiently to extend battery range as well as extending their brake life and reducing brake maintenance. “So far, we’ve seen virtually no maintenance required. We expect brakes to last a lot longer, no oil changes or other maintenance required by combustion engines,” said Maki. Lion’s Alexander, though, said proper driver training is
needed. “If you stomp on the brake pedal, then you’re just creating friction and that energy is dissipating as heat in your brakes versus you could have recaptured it by the [regenerative braking],” he said, adding that bus drivers also need to learn to lift their foot off the accelerator and allow the regenerative braking, which is continuously readjusting based on speed and load, to kick in. In addition to hill hold and regenerative braking, new
tires are being introduced to accommodate some of the higher torques applied with EVs. For example, Bridge- stone recently introduced an all-position radial tire, specially designed for electric buses. It offers ultra-low rolling resistance and high-load capacity. Goodyear also introduced the Electric Drive GT designed with an asymmetric tread pattern and specialized tread com- pound that provide enhanced all-season traction for EVs in various road conditions.
COURTESY OF FIRST STUDENT
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