Abstract: A hydrogen-redox flow battery assembly comprises one or more battery cells and is used to electrochemically generate and store electric power. Each battery cell includes a hydrogen chamber, an electrolyte chamber, a membrane electrode assembly positioned between the hydrogen chamber and the electrolyte chamber, a hydrogen reservoir and an electrolyte reservoir. The hydrogen-redox flow battery assembly is configured to allow an uncontrolled pressure difference between the pressure in the hydrogen chamber and the pressure in the electrolyte chamber, the pressure difference determined by a diffusion of protons through the membrane electrode assembly during a charge and/or a discharge operation. The one or more battery cells of the hydrogen-redox flow battery assembly is/are completely positioned in the hydrogen reservoir.