37 Internal Fire Exposure Test37.1

37 Internal Fire Exposure Test37.1 The electric energy storage system shall be designed to prevent a single cell failure due to thermal runaway within the system from cascading. The DUT (i.e. battery or module) shall be designed to prevent cascading from propagating beyond the DUT enclosure. This test is applicable to secondary lithium and sodium sulfur technologies.37.2 The fully charged electric energy storage system (MOSOC per 6.1) is to be subjected to the internal fire test which consists of heating one internal cell that is centrally located within the DUT until thermal runaway or otherwise forcing the failure of a cell through any means necessary and determining whether or not that failure does not cause the failure of neighboring cells. If cascading occurs, the cascading shall not propagate beyond the DUT. Regardless of the method used to fail the cell, cell failure is to occur withinat least 20 min. Once the thermal runaway is initiated, the mechanism used to create thermal runaway is shut off or stopped and the DUT is subjected to a 24-h observation period.Exception No. 1: Testing on a cell that is other than centrally located within the DUT may additionally be conducted if it is not clear which is the worst case scenario. The location of the failed cell is to be documented for each test