A high-voltage capacitor assembly, comprising a first capacitor unit; and an enclosure; the first capacitor unit comprising: a first capacitor; and a second capacitor; each of the first capacitor and the second capacitor comprising a stack of capacitor cells; each of the capacitor cells comprising an arrangement of a pair of elongate foil electrodes separated by a dielectric (20, 30), whereby the arrangement is multiply-folded in a substantially flat, wound configuration resulting in folded sections of the foil electrodes; wherein the first capacitor and the second capacitor are electrically connected in series and integrated into the enclosure; whereby the capacitor cells of the first capacitor and the second capacitor are electrically connected in series; adjacent capacitor cells of the stack of the capacitor cells of the first capacitor are electrically connected in series by a bridging element joining their foil electrodes on one longitudinal side of the foil electrodes; and adjacent capacitor cells of the stack of the capacitor cells of the second capacitor are electrically connected in series by bridging elements (13a, 13b) joining their foil electrodes on both longitudinal sides of the foil electrodes. a first capacitor unit; and an enclosure; the first capacitor unit comprising: a first capacitor; and a second capacitor; each of the first capacitor and the second capacitor comprising a stack of capacitor cells; each of the capacitor cells comprising an arrangement of a pair of elongate foil electrodes separated by a dielectric (20, 30), whereby the arrangement is multiply-folded in a substantially flat, wound configuration resulting in folded sections of the foil electrodes; wherein the first capacitor and the second capacitor are electrically connected in series and integrated into the enclosure; whereby the capacitor cells of the first capacitor and the second capacitor are electrically connected in series; adjacent capacitor cells of the stack of the capacitor cells of the first capacitor are electrically connected in series by a bridging element joining their foil electrodes on one longitudinal side of the foil electrodes; and adjacent capacitor cells of the stack of the capacitor cells of the second capacitor are electrically connected in series by bridging elements (13a, 13b) joining their foil electrodes on both longitudinal sides of the foil electrodes. a first capacitor; and a second capacitor; each of the first capacitor and the second capacitor comprising a stack of capacitor cells; each of the capacitor cells comprising an arrangement of a pair of elongate foil electrodes separated by a dielectric (20, 30), whereby the arrangement is multiply-folded in a substantially flat, wound configuration resulting in folded sections of the foil electrodes; wherein the first capacitor and the second capacitor are electrically connected in series and integrated into the enclosure; whereby the capacitor cells of the first capacitor and the second capacitor are electrically connected in series; adjacent capacitor cells of the stack of the capacitor cells of the first capacitor are electrically connected in series by a bridging element joining their foil electrodes on one longitudinal side of the foil electrodes; and adjacent capacitor cells of the stack of the capacitor cells of the second capacitor are electrically connected in series by bridging elements (13a, 13b) joining their foil electrodes on both longitudinal sides of the foil electrodes.