Abstract: Cartridge for refilling methanol or methanol/water as fuel to an electronic unit with a fuel cell. The cartridge includes a connection device comprising: an axially slidable cylinder (4) with an upper end that with a first sealing means (3) is brought sealingly through an inner cartridge wall (2) that constitutes the container for the fuel; passage way for fuel arranged along the cylinder, with opening (5) for fuel in at least two different distances from the upper end of the cylinder, of which both openings are located outside the inner cartridge wall with the cylinder in an outer position; a second sealing means (6) arranged at a lower end of the cylinder, sealing against an opening through an outer cartridge wall; a spring (8) arranged around the cylinder such that the first sealing means is pressed sealingly against the inner cartridge wall, and the second sealing means is pressed sealingly against the outer cartridge wall, such that the passage way for fuel is kept closed.