The present subject matter includes a first capacitor stack including a first plurality of anode layers and a first plurality of cathode layers and a second capacitor stack including a second plurality of anode layers and a second plurality of cathode layers. In various embodiments, a flexible bus is welded to the first capacitor stack and to the second capacitor stack. The flexible bus is adapted to conduct electricity between the first capacitor stack and the second capacitor stack. Also, the present subject matter includes embodiments where the first capacitor stack and the second capacitor stack are disposed in a case filled with an electrolyte.