All About Series | October 17, 2022
All About Range, Safety and Reliability

Electric school buses are reliable, safe and ready now to meet your district’s needs.

Image
A yellow school bus at a bus stop with blue skies, trees and American flag on a pole nearby.

Current electric school bus battery ranges can cover most bus routes

One of the most common questions about electric school buses is about their range: how far can they go on a single charge? Electric school buses are becoming more advanced, with longer ranges, with each new generation of bus. Many manufacturers are on their second or third iteration – and some even further along. Electric school buses currently have ranges of up to 210 miles for Type C buses; and all Type A, C and D buses listed offer over 100 miles of range, enough to cover most bus routes.

When examining the range of the bus, it is important to be aware of the advertised or “nameplate” battery capacity compared to its “usable” capacity. Many manufacturers will advertise the actual battery size (kWh) or nameplate capacity of a bus, but in reality, around 80% - 90% of that advertised capacity will be “usable.” Manufacturers reserve about 10-20% of the battery to maintain the battery state of health over the long run. Reserving some of the battery power also ensures that critical functionality will work and that the vehicle will not suddenly shut-off.

Should the charge level reach less than 10-20% (the bus will warn a driver when it approaches this range), the bus may eliminate power to external systems to conserve it for essential functions. This function is similar to fossil fuel vehicles that are low on fuel.

The range listed is typically based on simply running the bus only; however, other systems like heating and air conditioning would also use the battery and reduce mileage range. Notably, a wheelchair lift or ramp does not draw power from the high voltage battery that is responsible for propulsion – so there’s no impact on range. Instead, a separate 12-volt battery is used to power the lift and ramp.

In contrast, regenerative braking can capture extra energy, which could extend the range of the bus. Regenerative braking occurs on downhill rides or during slow stopping like at stop signs, traffic lights and bus stops, or while in traffic. It has an added benefit of lower wear and tear on braking systems.

Over the lifetime of an electric school bus, the battery will naturally degrade by around 20% after several years of use – similar to how a smart phone battery doesn’t last as long after a few years. If an electric school bus operator participates in vehicle-to-grid (V2G) or vehicle-to-anything (V2X) services, the added battery cycles may degrade the battery more quickly. 

Electric school buses are safe

There are certain risks inherent to working with high voltage systems – however, these risks are minimal, and issues are prevented with proper vehicle design, training and safety procedures much like the safety procedures for electrical work and in the automotive sector. Data show that battery fires are extremely rare. In a large study of passenger cars, the rate of fires was significantly higher in gasoline and hybrid cars compared to electric vehicles: gasoline vehicles had 1,530 fires per 100,000 vehicles, while electric vehicles experienced only 25 fires per 100,000 vehicles.

Battery fires, or thermal events, are typically prevented by keeping battery temperatures at reasonable ranges and monitoring any deviations (i.e., liquid cooling). In addition, built-in safety features of electric school bus models effectively protect students and drivers. Electric school buses are designed to the highest safety specifications to prevent thermal events, and school buses are among the safest vehicles on the road. Electric school buses are designed using specific battery chemistries, strategic placement of batteries in the middle of the undercarriage, high-impact protective battery coverings and automatic electrical disconnects that prevent incidents even in the case of a collision.

School districts and dealers can conduct safety trainings to help first responders better understand which buses in the fleet are electric, battery configurations and switch locations within the bus and how to suppress or extinguish electrical fires, just in case.  

In a large study of passenger cars, the rate of fires was significantly higher in gasoline and hybrid cars compared to electric vehicles.

Source

Electric school buses are reliably operating in a range of climates and geographic conditions

Electric school buses have been successfully deployed in a variety of climates with buses committed in 38 states, across urban, suburban and rural areas.

Electric school buses can operate in extreme temperatures due to battery thermal management systems that maintain an internal temperature range for optimal and safe battery function. For cold weather climates, including Alaska, Canada and Michigan, electric school buses can offer unique advantages. Unlike a diesel bus with weight concentrated in the front, electric buses’ battery weight is more evenly distributed between the front and rear wheels, improving driving ability in the snow. Cold weather conditions, however, can impact range if the heating system draws from the battery responsible for propulsion, but impacts vary. Three Rivers Community Schools outside of Kalamazoo, Michigan, has found that their electric buses have “outperformed [their internal combustion engine] buses in cold weather” but utilize a diesel heater. Salt Lake City School District in Utah, on the other hand, has seen its range drop around 18% in winter conditions due to an all-electric heater; they have, however, found that they can get around 16% additional range from regenerative braking. School districts can test conditions and plan routes that meet their needs. 

Buses have also been deployed in hot weather climates. Cartwright School District 83 outside of Phoenix, Arizona, received the state’s first electric school bus in July 2021. The bus has an upgraded air conditioning system that is appropriate for the Arizona heat and has successfully operated in summer temperatures without major battery impacts. While extremely high ambient temperatures can lead to battery overheating, an active cooling system in electric school buses helps maintain an optimal temperature around the battery, and a secondary safety system automatically shuts off the battery before major issues can arise. With this in mind, some school districts have opted not to operate their buses on extremely hot days during the summer but see promise as technology continues to evolve.

In addition to temperature, electric school buses have also seen success in a variety of geographic conditions from rural to urban to mountainous regions. The Eastern Band of Cherokee Indians has found its bus is performing well in North Carolina’s mountainous terrain, noting the added benefit of regenerative braking on the mountain declines. Similarly, the electric cooperative serving West Grand School District in Colorado noted that the electric school bus works “much better than a traditional diesel bus” on the district’s steep mountain passes, prompting the district to pursue more electric models. 

Share