Cycle life

Cycle life, which SMA documents call cycle stability, describes how long a battery will last. It is the number of times the battery can be charged and discharged before its available capacity drops below a set value given by the manufacturer. Batteries lose capacity and efficiency with age and with the energy that passes in and out of them. The loss starts even before the battery is installed. Manufacturers often give cycle life as a function of depth of discharge. Lead-acid batteries typically reach 1,000 or 2,000 cycles, and research on newer chemistries such as lithium-ion aims for 10,000 cycles. End of life depends on how the battery is used. Where reliability matters, a cell at 80% capacity after 1,000 cycles would likely be replaced. In less demanding uses, it might keep running to around 2,000 cycles and 60% capacity. Cycle life can also be based on internal resistance: the number of cycles before resistance rises by a set factor, such as 1.3 times the initial value. This avoids taking the battery out of service for a capacity test. Battery systems are usually specified by the capacity they must still have at end of life, not their capacity when new. This matters when sizing storage and judging when to replace it.

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• sentence 1: support check: partial - The SMA text defines cycle stability as the number of charge/discharge cycles before capacity falls below a manufacturer-specified value. Nothing in the passages equates cycle stability with the term cycle life.
• sentence 5: support check: partial - The resistance-based definition with the 1.3 times example is stated. The passage does not say that this avoids taking the battery out of service, though it is implied by the contrast with the capacity test.
• sentence 6: support check: partial - Specifying end-of-life capacity is stated. The claim that this matters for sizing and for judging replacement is not stated.
• sentence 1: review: partial - The SMA rows support the definition of cycle stability as a service-life measure tied to a manufacturer-specified capacity threshold, but nothing in them equates it with the term 'cycle life'. -->