FLUID SPRING PRESSURIZED BATTERY STACK

The present invention refers to a battery system (100) comprising a stack comprising a plurality of battery cells (10 ..., 10); fluid springs (30); and fluid pressure adjusting means (12,). The fluid springs (30) are positioned between a first and a second end plate (40a, 40b), and are configured for exerting a pressure on the battery cells. At least one of the fluid springs (30) comprises an elastic device, the elastic device having a predefined Young's modulus. The fluid pressure adjusting means (12) is connected to one or more fluid springs (30) comprising an elastic device is configured to generate an underpressure in the fluid within the connected fluid springs (30). Also, the battery system allows for avoiding or minimizing the risk of spill-over of a thermal runaway between different cells of the battery system. The present invention also refers to method for operating the battery system.