Survivability of thinner power sources such as flexible Li-ion batteries (LIB) when exposed to repeated charge-discharge cycles at different operating temperatures along with small mechanical twisting loads encountered in human body applications is relatively unknown. With the advancements in portable and densely packaged electronics, thin power sources, which are reliable and are needed to sustain the daily stresses of motion. The ability of thin form factors to operate reliably in presence of loads such twisting while simultaneously being exposed to different ambient temperatures is the major concern. Development of meaningful test protocols for reliability of the battery requires the replication of human body motion. A twisting test-stand capable of replicating the stresses of daily motion in a lab-environment has been developed for the test. The battery state assessment analyzer comprises of programmable source meter and electronic load, a multi-channel data acquisition system, LabVIEW user interface. A mechanical bending actuator controlled via microcontroller was used for subjecting the LIBs to bending loads. The microcontroller was programmed in a way such that 60 twisting cycles were performed during every discharge phase. A total of 150 charge-discharge cycles are conducted during the life cycle tests where each cycle is comprised of discharging to full depth, bending during discharging, and charging back to full voltage. The degradation of the batteries has been studied. FEM model has been developed for life prediction of the battery and for assessment of acceleration factors between test conditions and use conditions.