Coupling of cell to housing

Porous separator is sandwiched between electrode films with attached current collector foil to obtain an electrode sheet. The electrode sheet is formed into a jellyroll for use in a double layer capacitor. The jellyroll is inserted into a can through an open end to rest against the can's bottom. A collector plate is pressed against the jellyroll, crunching current collector foil protruding from each end of the jellyroll. The bottom and the collector plate include indentations of reduced thickness. Laser is applied to the indentations to weld the foil on each end of the jellyroll to the bottom or collector plate. The laser application pattern, for example, a zigzag pattern, results in the total length of laser welds along each indentation being considerably longer than the length of the indentation, reducing contact resistance between (1) the foil and the bottom, and (2) the foil and the current collector.