TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The battery enclosure system comprises an electric vehicle including a chassis and a body. The thermal-control agent is a fluid. The fluid includes a major portion of water. The obstruction includes a pressure-actuated valve. The pressure-actuated valve opens upon application of an ingress force applied to the valve from outside the enclosure and remains closed upon application of an egress force applied to the valve from inside the enclosure. The ingress force is 3-100 psi, preferably 10-50 or 20-80 psi and where the egress force is less than the ingress force. The obstruction includes a mechanically-weakened access plate. The plate breaks opens upon application of an ingress force applied to the valve from outside the enclosure and remains closed upon application of an egress force applied to the plate from inside the enclosure. The fill port includes a mechanical fitting interoperable with first responder thermal control agent dispensing systems. The mechanical fitting includes a fastener with NHS threads. The mechanical fitting includes a mechanical interlock to secure an element of the dispensing system to the mechanical fitting permitting application of the ingress force to the fill port by dispensation of the thermal-control agent through the mechanical fitting. The system further comprises an exit valve coupled to a second portion of the wall of the enclosure where the exit valve provides for egress of gas displaced by ingress of the thermal-control agent. The second portion of the wall includes a location permitting egress of a sufficient volume of the internal gas so the internal gas does not prevent thermal control of any internal battery cell by the thermal-control agent provided inside the enclosure through the fill port. The system further comprises a first exit valve coupled to a second portion of the wall of the enclosure where the exit valve provides for egress of a hot gas generated during a sustained thermal event of the batteries, where the second portion of the wall displaced from the fill port sufficiently to reduce exposure of an operator of the fill port to the hot gas. The first exit valve provides for egress of gas displaced by ingress of the thermal-control agent. The system further comprises a second exit valve coupled to a third portion of the wall of the enclosure where the second exit valve provides for egress of gas displaced by ingress of the thermal-control agent. The enclosure is coupled to the chassis and where the fill port is structurally isolated from access external to the vehicle. The fill port further comprises a fill port coupler, which includes an externally accessible port and a passageway (120) communicating the externally accessible port to the enclosure. The passenger vehicle includes a first orientation having the fill port externally accessible and the passenger includes a second orientation having the fill port blocked from external access, the system further comprises a second fill port coupled to a second portion of the wall of the enclosure, the second fill port includes a second selectably permeable obstruction allowing an ingress of a thermal-control agent into the enclosure through the second fill port while inhibiting an egress of a gas out of the enclosure through the second fill port, the second fill port is structurally isolated from access external to the vehicle, the second fill port further comprises a second fill port coupler, the second coupler includes a second externally accessible port and a second passageway communicating the second externally accessible port to the enclosure while the passenger vehicle is in the second orientation.