NOVELTY - A fuel cell comprises: (i) a casing; (ii) a first chamber configured to retain liquid fuel and defined at least partially by a first surface of an anode; and (iii) a second chamber configured to retain liquid electrolyte and defined at least partially by a second surface of the anode and a first surface of a cathode. The fuel cell is configured to be sealed in a liquid-tight manner during at least a portion of its service life.    USE - For supplying electrical energy to a device e.g. portable telecommunications device, cellular phone, portable computer, personal digital assistant (PDA), audio device, video device, or medical device having a power capacity of up to 150 W (claimed).    ADVANTAGE - The assembly provides a fuel cell that is capable of being operated in a sealed state, similar to a battery. The sealed fuel cell can be reused after the liquid fuel and/or the liquid electrolyte are exhausted.    DETAILED DESCRIPTION - A fuel cell (12) comprises a casing; a cathode having a first surface and a second surface, wherein at least part of the second surface is exposed to the atmosphere; an anode having a first surface and a second surface; a first chamber configured to retain liquid fuel and defined at least partially by the first surface of the anode; and a second chamber configured to retain liquid electrolyte and defined at least partially by the second surface of the anode and the first surface of the cathode. The fuel cell is configured to be sealed in a liquid-tight manner during at least a portion of its service life.    INDEPENDENT CLAIMS are also included for:    (1) a cartridge (14) for refreshing a refillable fuel cell comprising fuel chamber(s) at least partially filled with liquid fuel and an electrolyte chamber at least partially filled with liquid electrolyte;    (2) a method of supplying electrical energy to a device comprising providing a fuel cell; and electrically connecting the fuel cell to the device;    (3) a method of refreshing a self-contained fuel cell by connecting a cartridge to the fuel cell;    (4) a fuel cell system comprising a fuel cell assembly (16); and a cartridge removably connected to the fuel cell;    (5) a fluid replacement system (70) for replacing a spent liquid contained in a fuel cell comprising a storage chamber configured to contain a first replacement liquid; a first port in fluid communication with the storage chamber and connectable with one of the refilling ports; a second port in fluid communication with the storage chamber and connectable with another refilling port; and a fluid flow actuating arrangement configured to remove at least part of spent liquid from the fuel cell via the second port and to supply at least some replacement liquid to the fuel cell via the first port;    (6) a port arrangement for transferring a liquid between a fuel cell and a cartridge comprising a first port and a second port configured to open when the ports are connected; and an absorbent component disposed between the first port and the second port, wherein the first and second ports together defining a dead space are configured to close when disconnected from each other and the dead space has a volume less than or equal to an absorbency capacity of the absorbent material; and    (7) a liquid replacement method comprising at least partially removing an at least partially spent liquid fuel from a first chamber of a fuel cell; and transferring a replacement liquid fuel into the first chamber, wherein removing and transferring occur simultaneously.    DESCRIPTION OF DRAWING(S) - The figure shows a perspective view of a refillable fuel cell system.    Fuel cell (12)    Cartridge (14)    Fuel cell assembly (16)    Valves (38, 40, 46, 48, 74, 76, 82, 84)    Fluid replacement system (70)    Interlocking mechanism (132)