A battery pack and battery pack chassis are described. The battery pack includes a chassis that is configured to position multiple cells proximate to one another within the pack, while also providing areas through which a potting compound can flow and contact the cells. For example, the chassis can include spacers or ribs that separate the cells, in some cases in asymmetric configurations, such that the potting compound contacts the outer surface of each battery cell within the pack. The chassis, in some cases, can also facilitate the connection of a bus bar between battery cells.