A hydrogen-redox flow battery assembly comprising: - one or more battery cells, each battery cell comprising: - a hydrogen chamber configured to house a flow path of hydrogen gas between a hydrogen inlet and a hydrogen outlet; - an electrolyte chamber configured to house a flow path of liquid electrolyte between an electrolyte inlet and an electrolyte outlet; - a membrane electrode assembly comprising a hydrogen electrode connected to said hydrogen chamber and an electrolyte electrode connected to said electrolyte chamber, and a membrane positioned between said hydrogen chamber and said electrolyte chamber, said membrane electrode assembly configured to only allow a diffusion of protons through said membrane electrode assembly between said hydrogen gas in said hydrogen chamber and said liquid electrolyte in said electrolyte chamber; - a hydrogen reservoir connected to said hydrogen chamber of said one or more battery cells and configured to retain said hydrogen gas; and - an electrolyte reservoir connected to said electrolyte chamber of one or more battery cells and configured to retain said liquid electrolyte; CHARACTERIZED IN THAT: - said hydrogen-redox flow battery assembly is further configured to allow an uncontrolled pressure difference between the pressure in said hydrogen chamber of said battery cell and the pressure in said electrolyte chamber of said battery cell, wherein said pressure difference is determined by said diffusion of protons through said membrane electrode assembly during a charge and/or a discharge operation; and - said one or more battery cells of said hydrogen-redox flow battery assembly is/are completely positioned in said hydrogen reservoir. - one or more battery cells, each battery cell comprising: - a hydrogen chamber configured to house a flow path of hydrogen gas between a hydrogen inlet and a hydrogen outlet; - an electrolyte chamber configured to house a flow path of liquid electrolyte between an electrolyte inlet and an electrolyte outlet; - a membrane electrode assembly comprising a hydrogen electrode connected to said hydrogen chamber and an electrolyte electrode connected to said electrolyte chamber, and a membrane positioned between said hydrogen chamber and said electrolyte chamber, said membrane electrode assembly configured to only allow a diffusion of protons through said membrane electrode assembly between said hydrogen gas in said hydrogen chamber and said liquid electrolyte in said electrolyte chamber; - a hydrogen chamber configured to house a flow path of hydrogen gas between a hydrogen inlet and a hydrogen outlet; - an electrolyte chamber configured to house a flow path of liquid electrolyte between an electrolyte inlet and an electrolyte outlet; - a membrane electrode assembly comprising a hydrogen electrode connected to said hydrogen chamber and an electrolyte electrode connected to said electrolyte chamber, and a membrane positioned between said hydrogen chamber and said electrolyte chamber, said membrane electrode assembly configured to only allow a diffusion of protons through said membrane electrode assembly between said hydrogen gas in said hydrogen chamber and said liquid electrolyte in said electrolyte chamber; - a hydrogen reservoir connected to said hydrogen chamber of said one or more battery cells and configured to retain said hydrogen gas; and - an electrolyte reservoir connected to said electrolyte chamber of one or more battery cells and configured to retain said liquid electrolyte; - said hydrogen-redox flow battery assembly is further configured to allow an uncontrolled pressure difference between the pressure in said hydrogen chamber of said battery cell and the pressure in said electrolyte chamber of said battery cell, wherein said pressure difference is determined by said diffusion of protons through said membrane electrode assembly during a charge and/or a discharge operation; and - said one or more battery cells of said hydrogen-redox flow battery assembly is/are completely positioned in said hydrogen reservoir.