Provided are battery packs and interface modules for electrically interconnecting electrochemical cells in the packs and for providing heat distribution with the packs. An interface module interfaces one side of all electrochemical cells in a battery pack. The interface module may have a substantially planar shape such that the space occupied by the module in the battery pack is minimal. Most, if not all, conductive components of the interface module may be formed from the same sheet of metal. In some embodiments, the interface module includes multiple bus bars such that each bus bar interconnects two or more terminals of different electrochemical cells in the battery pack. Each bus bar may have a separate voltage sense lead extending from the bus bar to a connecting portion. The bus bars may be flexibly supported within the module. The interface module may also include multiple thermistors disposed on different bus bars.