The invention relates to a rechargeable battery unit, in particular for a watercraft, having a plurality of rechargeable batteries which are connected to one another by means of a holding arrangement to form a rechargeable battery cell, wherein the holding arrangement has at least one holder which forms receptacles by means of which the rechargeable batteries are held in the region of a pole end, and that at least some of the rechargeable batteries are electrically coupled to one another in the region of their poles by means of a pole connector. A design of this kind allows a powerful rechargeable battery unit to be constructed with a compact installation space, it also being possible for the rechargeable battery cells to be cascaded for the purpose of varying the energy density and/or voltage in said rechargeable battery unit. A rechargeable battery unit of this kind is suitable, in particular, for use in motor-operated watercraft.