No matter how thick the separator is used, after Jelly Roll wound, the effective distancebecomes shorter because the surface of the electrodes are rugged, and some smallparticles/burrs may break through “PART” of the separator (that is why most of LIBJelly Rolls BDV are much lower than the separator’s original BDV; 600V~1,000V perour experience for a normal jelly roll). Point is, what is the considered SAFE insulation distance, which is able to resist thefurther inflation of the cathode while battery cell is being charged. The test voltageneeded for finding the insufficient insulation distance, of course MUST at least higherthan the air BDV at this gap distance