New video released by the MBTA on Friday shows the moment an explosion led to a battery failure on trains, which prompted new train cars to be pulled from service once again in late June.
The video shows, from a distance, sparks flying in a train yard.
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The new Orange and Red line train cars were removed from service June 20 after one of the Orange Line cars experienced what the MBTA described at the time as a battery failure at the Wellington Yard.
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The train was out of service at the time, but the MBTA removed all the new cars from service while engineers and technicians worked to identify the issue's cause, noting safety is the agency's "top priority."
According to the transportation agency, the battery that failed "provides low-voltage DC power, controlling the electrical equipment on the vehicle and powering lighting, signage, and communications equipment."
The train manufacturer, CRRC, and the MBTA worked together to identify the cause of the problem as an out-of-range battery temperature reading, which caused the battery to "overcharge for an extended duration and fail," officials have said
A design change was made that increases airflow in the battery compartment, the agency said. Additionally, a modification to the temperature sensing circuitry "was developed, implemented, and successfully tested over the weekend."
The new cars recently returned to service, and the MBTA said it was grateful to T riders for their patience while engineers worked to ensure the cars are safely and reliably performing.
