Editing Memory effect (section)

===Permanent loss of capacity===

====Deep discharge====
Some rechargeable batteries can be damaged by repeated deep discharge. Batteries are composed of multiple similar, but not identical, cells. Each cell has its own charge capacity. As the battery as a whole is being deeply discharged, the cell with the smallest capacity may reach zero charge and will "reverse charge" as the other cells continue to force current through it.  The resulting loss of capacity is often ascribed to the memory effect.

Battery users may attempt to avoid the memory effect proper by fully discharging their battery packs. This practice is likely to cause more damage as one of the cells will be deep discharged. The damage is focused on the weakest cell, so that each additional full discharge will cause more and more damage to that cell. Repeated deep discharges can exacerbate the degradation of the weakest cell, leading to an imbalance in the battery pack, where the affected cell becomes a limiting factor in overall performance. Over time, this imbalance can result in reduced capacity, shorter run times, and the potential for overcharging or overheating of the other cells, further compromising the battery's safety and longevity.

====Age and use—normal end-of-life====
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-ion 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.<ref>[https://web.archive.org/web/20161107091002/http://www.thermoanalytics.com/products/battery-module/hev-management Battery Types and Characteristics for HEV] ThermoAnalytics, Inc., 2007. Retrieved 2010-06-11.</ref> The lifetime of lithium batteries decreases at higher temperature and [[state of charge|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.<ref>{{cite web|title=Lithium-Ion Battery Maintenance ZZZ Guidelines|url=http://www.newark.com/pdfs/techarticles/tektronix/LIBMG.pdf|publisher=Tektronix, Inc.|access-date=16 December 2013}}</ref><ref>{{cite web|title=Lithium-Ion & Lithium Polymer Cells and Batteries Safety Precautions like|url=http://ultralifecorporation.com/download/168/|publisher=Ultralife corporation|access-date=16 December 2013}}</ref>