A method of assembling a power module includes placing a first plurality of cells adjacent to one another to form a first cell layer. A flexible circuit layer is positioned above the first cell layer, the flexible circuit being electrically conductive. A second plurality of cells is positioned adjacent to one another to form a second cell layer aligned with the first cell layer such that the flexible circuit layer is sandwiched between the first cell layer and the second cell layer. The flexible circuit layer is folded along each of a plurality of axes of rotation such that each one of the first plurality of cells faces another one of the second plurality of cells. Each of the first plurality of cells and the second plurality of cells has respective first and second tabs (extending from their respective short ends) which are welded to the flexible circuit layer.