As longer driving range becomes an important feature for pure electric vehicles, higher energy density power batteries are needed.  However, the battery safety for higher energy density power batteries has been an obstacle.   An idea of “Fail-Safe” and its measures can largely reduce the risk of using high energy density power Li – Ion batteries. This talk will describe how our Fail-Safe system working to prevent the overall packs disasters when few cell had thermo runaway inside the battery pack.