All rechargeable batteries have a finite lifespan and will slowly lose storage capacity as they age due to secondary chemical reactions within the battery whether it is used or not. Some cells may fail sooner than others, but the effect is to reduce the voltage of the battery. Lithium-based batteries have one of the longest idle lives of any construction. Unfortunately the number of operational cycles is still quite low at approximately 400–1200 complete charge/discharge cycles. The lifetime of lithium batteries decreases at higher temperature and states of charge (SoC), whether used or not; maximum life of lithium cells when not in use(storage) is achieved by refrigerating (without freezing) charged to 30%–50% SoC. To prevent overdischarge, battery should be brought back to room temperature and recharged to 50% SoC once every six months or once per year.