NOVELTY - The method involves monitoring battery pack temperature, and determining when the battery pack temperature exceeds preset temperature. A determination is made whether electrical isolation resistance falling below preset resistance occurs within a preset time period of the battery pack temperature exceeding the preset temperature. A predetermined cell failure response is performed when the electrical isolation resistance falling below the preset resistance value occurs within the preset time period of the battery pack temperature exceeding the preset temperature.    USE - Method for detecting and responding a failure of a cell within a single piece or multi-piece high voltage rechargeable battery pack in an electric vehicle e.g. hybrid vehicle or plug-in hybrid electric vehicle, utilizing all-electric drive trains insure safety of vehicle passengers, service technicians, crash site first responders and bystanders. Uses include but are not limited to loss of voltage chain continuity, spike in battery pack temperature, sudden increase in the relative humidity within the battery pack, and a spike in the monitored temperature of coolant used to cool the battery pack, of a cell e.g. lithium ion cell such as lithium iron phosphate cell and lithium cobalt oxide cell, lithium ion polymer cell, nickel metal hydride cell, nickel cadmium cell, nickel hydrogen cell, nickel zinc cell, and silver zinc cell.    ADVANTAGE - The method enables modifying a load on a battery pack once a cell failure event is detected, so that the load can be reduced or eliminated if a thermal event detected by the system is a precursor to thermal runaway, thus preventing increase of battery temperature, and providing time to eliminate/minimize damage to adjacent cells and materials, and hence preventing battery thermal runaway in an efficient manner and minimizing system complexity, weight and cost.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow chart illustrating a method for detecting and responding a failure of a cell.    Step for determining isolation resistance of battery pack (1101)    Step for comparing isolation resistance of battery pack to a preset resistance value (1103)    Step for monitoring the isolation resistance of the battery pack when isolation resistance is greater than a preset resistance value (1105)    Step for determining whether preset resistance value is less than a preset resistance value (1107)    Step for determining whether secondary evidence of a cell failure occurs (1801)    Step for following an alternate set of response instructions (1803)