An exploded view of a passive environmental management module 40 is shown in FIG. 4. When assembled, the passive environmental management module 40 is attached to the back wall of the active battery module 20. A gasket 58 seals the passive environmental management module 40 to the back wall of the active battery module 20. A cover 41 is provided with one port for each duct/fan. The cover further attaches to a heat sink 42 comprised of a third exterior wall 48 and cooling fins 44. The third exterior wall 48 includes an inner surface an inner surface 48a and an outer surface 48b. The fins are mounted parallel to each other on the inner surface 48a and aligned to a fin axis 44y. An overpressure relief port 46 is formed in third exterior wall 48 that vents heat and smoke from a faulty battery cell out of module 40 in a vent direction 46z. The housing is placed in a stack arranged along a stack axis 12x. A Cartesian coordinate system having three mutually perpendicular coordinate axes is formed by the stack axis 12x, the fin axis 44y, and the 46z.