Railway vehicle electrical devices, such as driving system, such as auxiliary power system is the basic system of railway vehicle.

铁道 车辆电气装置如驱动系统、辅助电源系统等，是铁路车辆的基本系统。

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The 787 has two identical lithium-ion batteries, one of which is located toward the front of the plane and powers cockpit electrical systems, the other toward the rear and used to start an auxiliary power unit while the plane is on the ground, among other functions.

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Richard Walsh, a Massport spokesman, said the jet's auxiliary power unit battery, which is housed in a small compartment known as the aft electrical equipment bay, exploded after crews believed the fire was extinguished.

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