Air duct device, battery rack system and control method of air duct device

The invention belongs to the technical field of batteries, and discloses an air duct device, a battery rack system and a control method of the air duct device, the air duct device is used for exhausting air into a battery rack, and the air duct device comprises a plurality of first plate body assemblies, a plurality of second plate body assemblies and a third plate body assembly, the first plate assemblies and the second plate assemblies are detachably connected in a staggered mode in the vertical direction to form an air bellow, the edges of the two opposite side walls of the air bellow can be detachably connected with the battery rack, the top and the bottom of the air bellow are provided with a first opening and a second opening respectively, and external cold air can enter the air bellow through the first opening and can enter the air bellow through the second opening. And the third plate body assembly is detachably plugged at the second opening and is detachably connected with the battery rack, the struc