Abstract: The present invention provides a module for retaining and cooling a group of primary or secondary electrochemical cells for use in powered devices. To provide more effective cooling and reduce thermal gradients, cells are aligned in a side-by-side configuration within a multi-pass cooling passage. The multi-pass cooling in each module results in potentially longer useful life for the entire array. Large array batteries are formed of multiple modules, the shape and configuration of the modules allowing a variety of compact combinations having high energy density. In one configuration of an array battery according to the invention, two decks of modules are stacked vertically within a rigid enclosure. Air as a cooling medium is induced through each module to reduce cell temperatures. Temperature monitoring of each cell in a module and array allow for maintenance and identification of thermal events effecting continued long term operation.