BYD’s prototype electric transit school bus on display last month at the STN EXPO Indianapolis features a fire suppression system.
lithium-ion batteries as hazardous cargo and banned them on all commercial passenger flights. Still, the FAA reportedly recorded 46 incidents in 2018 of smoking or burning lithium batteries on passenger planes or in airports, up from 31 the previous year. Electronic devices powered by lithium-ion batteries
were then banned from cargo holds but were allowed as carry-on items, only after flight crews underwent supplemental training on how to deal with battery fires in electronic devices. Larry Rambeaux, a member of the Technology and
Maintenance Council that advocates for unbiased standards for the trucking industry, explained there are many different types of lithium batteries, but they all get lumped together as lithium ion. “There are many different additives and ratios,” he noted. “You could talk for weeks about the different batteries and how to treat them.” Rambeaux noted that lithium-ion’s bad reputa- tion started when cell phones caught fire, which scared a lot of people. He added that latter day lithium-ion batteries are safe
for school buses, if they are manufactured in a reputa- ble factory. “I feel confident about that,” he said. “Where I have fears and reservations is that people have heard these great things about lithium [and] they want to put them in chassis that weren’t designed for them,” he said. “The charging system of the vehicle depends on the chemistry of the battery, so you may have to make changes to the charging system of the vehicle.” Rambeaux also espoused the vital aspects of a thermal management system, or TMS.
Safety First Rambeaux said electric school bus owners should-
make sure they receive training from their vehicle and battery manufacturer, adding that lithium can be very temperamental. “It can be damaged from being too hot or too cold, undercharged or overcharged,” he said. “Just because it is lithium does not mean it’s all the same. We’re talking about a battery pack that has several hundred
38 School Transportation News • JULY 2022
volts. So, foremost in my opinion, if you’re not properly trained you shouldn’t touch them. You’re at voltage levels now that are lethal.” As a result, OEMs and school districts must mirror the airlines and train staff and students on safety regimens that are in line with the unique challenges presented by the potential for the types of thermal events caused by the powerful lithium-ion alternative to fossil fuels. Primary on the list of things to do was to improve the chemistry of the batteries to make them safer and less volatile while sacrificing as little power as possible. The batteries should also be located in a protected space with a stabilized temperature. The OEMs interviewed for this article said they’ve done just that. Lion Electric Company spokesman Brian Alexander
shared that the battery-electric school bus (BESB) man- ufacturer developed a battery that uses a lithium nickel manganese cobalt oxide chemistry (NMC), a recipe he explained that has high energy density for staying power and renders them less prone to thermal events. Alexander, Lion’s director of public relations, add-
ed that it is critical to control the temperature of the battery’s environment. One very important aspect to en- suring optimal performance in all conditions is to keep the batteries in the optimal temperature range, about 70 degrees Fahrenheit. He noted that this is accomplished with active cooling.
“A TMS is very important,” he said. “[Our battery] has high energy density and thermal stability as well as a longer lifecycle than some other types of Li-ion batteries.” Maintaining an optimum temperature for a battery
electric school bus means having a TMS that provides heat in cold climates, insulation for extreme weather, and ventilation, according to the website for Elmelin Industrial Insulation Solutions, which specializes in industrial insulation solutions for high voltage and high temperature applications. The advice continues that a TMS must prevent thermal runaway, a chemical reaction that can cause a battery fire to reignite by re-generat- ing excessive heat even after it has been extinguished.
PHOTO BY VINCENT RIOS CREATIVE
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