August 2016 - Catastrophic failure concerns impede penetration of Li-ion batteries in electric vehicle and energy storage markets. Unfortunately, no fast method to forecast catastrophic failure has existed. This work presents a solution by very early detection of nascent internal shorts that are precursors of catastrophic failure. The new metric, the self-discharge current, which is determined under potentiostatic conditions at a slight discharge overvoltage, is proposed as a fast metric for detection of shorts and assessment of battery safety. The method is non-invasive and applicable to any battery chemistry or design. It is easily adaptable to any battery management system for monitoring battery state of health at any time and at any battery state of charge. The technology based on this method can be used in electric drive vehicles, stationary energy storage, military, aeronautic, as final control in battery production, for first responders in electric vehicle accidents, and many other applications.