New Haven Register (New Haven, CT)
NTSB: Moisture in battery caused 2022 electric bus blaze
HAMDEN — A fire that erupted from a CTtransit electric bus while it was parked at a maintenance facility nearly two years ago likely was sparked by moisture inside the vehicle’s battery, authorities concluded.
The resulting fire sent two CTtransit maintenance workers to the hospital for smoke inhalation, and required firefighters to respond three times before it was fully extinguished, according to the findings of the National Transportation Safety Board.
NTSB investigators found that the probable cause of the bus fire “was moisture in the high voltage lithium-ion battery system, which led to battery damage resulting in the fire,” the report said.
The fire began on July 23, 2022, while the “battery electric transit bus” was parked inside the transit system’s maintenance facility in Hamden, the NTSB said.
Officials had taken the bus out of service two days prior because of an “error in the bus charging system,” the report said.
Around 3:40 a.m,, the bus began emitting smoke inside the facility, the report said. Firefighters responded and did not see any “visible flames,” the report said. So crews pushed the vehicle outside to an isolated parking spot.
“In the process, two CTtransit maintenance workers suffered smoke inhalation and were treated at an area hospital,” the report said.
Later that morning, the bus started emitting smoke again, along with fire from the rear of the bus. Firefighters came back to the scene, where the incident commander decided to let the bus burn.
“The fire remained active for several hours and fully consumed the vehicle. Following the departure of fire personnel, the bus continued to smolder while remaining isolated in the parking lot,” the report said.
Two days later, smoke and an “orange glow” were seen in the wreckage of the bus, the NTSB report said. Firefighters once again came out and doused the battery compartment, the NTSB said.
There were no other injuries reported in connection with the incident, according to the agency.
The report notes that after the fire in Hamden, the Federal Transit Administration issued new guidance about using electric transit buses in a handbook. The new guidance dealt with handling the risk of high voltage fires, including storing buses outdoors and having an isolation area in the event a bus were to catch fire.
“As transit agencies continue to electrify their bus fleets, the NTSB will continue to monitor issues related to BETB fires and ongoing research in the area to understand the safety impacts of these alternative-fueled vehicles,” the report said.