The new Orange and Red line train cars were back in service on Monday, two weeks after a reported battery failure in one of the cars led them to be pulled from service for inspection, the MBTA said in a statement.
A new and out-of-service Orange Line car experienced a failure within its battery compartment on June 20 at the Wellington Yard, according to the Massachusetts Bay Transportation Authority, and the agency removed all of its new Orange and Red line cars from passenger service to inspect them.
The battery controls the electrical equipment on the vehicle and powers lighting, signage, and communications equipment, according to the MBTA. While the cars have been out of service, vehicle engineers and technicians have been working to identify the cause of the failure.
The maker of the cars, CRCC, and the MBTA have identified the cause of the problem to be an “out-of-range battery temperature reading,” the statement said. This caused the battery to “overcharge for an extended duration and fail.”
A design change has since been made “to increase airflow in the battery compartment,” and engineers modified the temperature sensing circuitry and tested it over the weekend, according to the MBTA.
Rail experts previously told the Globe that a battery explosion was likely behind the agency’s decision to pull the new trains from passenger service.
The battery incident is one of a slew of recent safety-related problems with the MBTA, which is currently under investigation by the Federal Transit Administration.