Lithium-ion batteries are used for ion motion between the positive and negative electrodes. In theory, this mechanism should always be effective, but cycling, high temperatures and aging can degrade performance over time. Manufacturers adopt a conservative approach and specify the lithium-ion lifetimes in most consumer products range from 300 to 500 discharge and charge cycles.
Evaluating battery life during the counting cycle is not decisive, as the depth of the discharge may be different and there is no well-defined cycle composition criteria. Instead of loop counting, some device manufacturers recommend replacing the battery on the date stamp, but this method is not considered. Due to extensive use or unfavorable temperature conditions, the battery may fail within a specified time; however, most packages last much longer than the seals.
Battery performance is measured by capacity, which is a leading health indicator. Internal resistance and self-discharge also work, but these are less important in predicting the end of modern lithium-ion battery life.