Alternative Fuels

California district pilots electric drive system on bus

Kelly Aguinaldo
Posted on March 27, 2014
TransPower’s ElecTruck Drive System has been retrofitted on a Thomas Built Buses Saf-T-Liner HDX school bus, and it is being tested at California’s Escondido Union High School District.

TransPower’s ElecTruck Drive System has been retrofitted on a Thomas Built Buses Saf-T-Liner HDX school bus, and it is being tested at California’s Escondido Union High School District.

ESCONDIDO, Calif. — A local school district is currently participating in a month-long pilot program to test an electric drive system from TransPower that’s designed for several types of vehicles, including Type C and Type D school buses.

The ElecTruck Drive System has been installed in the chassis of a Thomas Built Buses Safe-T-Liner HDX unit that is owned by TransPower and is being leased to Escondido Union High School District.

Director of Transportation Robert Berkstresser told SBF that his operation became involved in piloting the technology after he and transportation officials at several other districts in San Diego County were approached by the county's air pollution control district.

“When the time came to put the bus on the road, we helped with registration and Highway Patrol certification, so we got the first crack at operating the bus for student service,” Berkstresser said.

He added that during the month-long test period, the data being tracked include the battery stability, motor efficiency and the reserve percentage of energy after a route.  

So far, Berkstresser has seen a savings in energy costs as a result of running the bus.

“The electric cost is about half of what our typical diesel bus would be for the same distance,” he said. “We will not have the bus long enough to access maintenance costs and compare them to a diesel bus. We do know that there will be cost savings on periodic inspections.”  
The bus is running on a fixed route due to mileage constraints that stem from the electric system. But Berkstresser said a bus outfitted with the ElecTruck Drive System could be used for special-needs or regular-education routes.

“At some point I anticipate owning electric vehicles in our fleet,” he said. “We would most likely use them in special-ed operations.”

The ElecTruck Drive System has a range of 60 to 80 miles, according to TransPower President and CEO Michael Simon. The system includes a proprietary automated manual transmission and a high-power, bi-directional onboard charger.

Joshua Goldman, vice president of business development for TransPower, told SBF that in installing the ElecTruck Drive System in a school bus, the diesel engine is replaced with an electric motor, and other accessories that are normally powered by a diesel engine are replaced with an electric drive. The batteries are placed in a reinforced underfloor luggage compartment.

The California Air Resources Board is funding a six-month pilot program, administered by the Air Pollution Control District of San Diego County, that includes the bus in operation at Escondido Union High School District.

“The purpose of the program is to evaluate the performance and range of the current system as installed in the Thomas Built Saf-T-Liner HDX chassis,” Goldman said. “The system is available to the marketplace today for similar trial programs, and it will be available for larger scale pilot production runs as soon as 2015. Within two to five years, the commercial prices of the system will come down as market volume increases.

"Also, the range will increase as batteries get cheaper, lighter and higher density. The batteries are scalable in size to easily double the current range of this bus for routes that require longer hauls. For future demonstrations, investments in larger infrastructure by school districts will allow for the 90-minute battery charge time, also allowing for greater daily use of this system.”   

Michael Simon added that TransPower has plans to convert six Type C school buses to electric drive under a project that’s scheduled to begin in May, with deployment of the buses by May 2015. The project will be performed under the auspices of the Clinton Global Initiative. 

“We are actively seeking opportunities to involve additional school districts in this demonstration and to go well beyond six buses,” Simon said. “So, while we don’t consider our system ready to install in hundreds of buses at this moment, we will have at least 20 medium- and heavy-duty trucks and buses operating with the same basic components by the time the six (or more) new buses are delivered in just over a year. If these efforts go well, then we could be starting to discuss an order for as many as 50 or 100 buses within this general time frame.”  

For more information on TransPower, which is based in Poway, Calif., visit the company’s website,

Related Topics: alternative fuels, California

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