“A battery pack has an enclosure that contains a plurality of batteries and conductors and that resists the flow of fluid between an interior of the enclosure and an exterior of the enclosure. An exit vent formed in the enclosure at a first location allows exhaust gas to flow from the interior of the enclosure to the exterior of the enclosure. A fill port formed in the enclosure at a second location, in an impermeable state, prevent ingress of fluid from an exterior of the enclosure to an interior of the disclosure. The fill port, in a permeable state achieved by receipt of a perforation tool there through, permits ingress of a sufficient amount of a thermal-control liquid into the enclosure through the fill port to terminate a runaway thermal event in the battery pack. A fill port coupler having a passageway and an externally accessible port may be included.”
