Abstract. Battery is major component of smartphone, but only selected samples are periodically examined due to numerous numbers of batteries. The Consumers are generally required the use of high energy density batteries. However, most consumers are often dissatisfied with the battery life from even the most advanced lithium-ion rechargeable batteries in mobile phone. If cracks are not detected, such a cracking mechanism could lead to unstable rupture of the battery. Up to this time, integrity evaluations are performed using conventional deterministic approaches. So it is expected that the results obtained are too conservative to perform a rational evaluation of lifetime. In this respect, a probabilistic safety assessment method is more appropriate for the assessment of overall battery safety. This paper describes failure probability estimation of the battery using fuzzy knowledge processing. Failure assessment diagram (FAD) of battery material is proposed and applied in the probabilistic analysis.