Memory effect, often known as battery impact, lazy battery effect, or battery memory, is an impact noticed in nickel-cadmium rechargeable batteries that causes them to hold less charge. It describes the scenario during which nickel-cadmium batteries gradually lose their maximum power capacity if they are repeatedly recharged after being solely partially discharged. The battery seems to "remember" the smaller capacity. The time period "memory" got here from an aerospace nickel-cadmium application in which the cells have been repeatedly discharged to 25% of available capability (give or take 1%) by exacting pc management, then recharged to 100% capacity with out overcharge. This long-term, repetitive cycle régime, with no provision for overcharge, resulted in a loss of capability past the 25% discharge level. True memory-impact is particular to sintered-plate nickel-cadmium cells, and is exceedingly troublesome to reproduce, especially in decrease ampere-hour cells. In a single explicit test program designed to induce the effect, none was discovered after more than seven hundred precisely-managed cost/discharge cycles.

In the program, spirally-wound one-ampere-hour cells were used. In a follow-up program, 20-ampere-hour aerospace-kind cells have been used on the same take a look at régime; Memory Wave Protocol effects have been observed after a few hundred cycles. Phenomena which are not true memory results may additionally happen in battery sorts other than sintered-plate nickel-cadmium cells. Specifically, lithium-based cells, not normally subject to the memory impact, might change their voltage ranges so that a digital lower of capacity could also be perceived by the battery management system. A common process usually ascribed to memory impact is voltage depression. In this case, the output voltage of the battery drops more quickly than normal as it is used, though the entire capacity stays nearly the identical. In trendy electronic gear that screens the voltage to indicate battery cost, the battery seems to be draining very quickly. To the user, it appears the battery shouldn't be holding its full cost, which seems much like memory impact.

That is a standard problem with excessive-load gadgets reminiscent of digital cameras and cell phones. Voltage depression is attributable to repeated over-charging of a battery, which causes the formation of small crystals of electrolyte on the plates. These can clog the plates, increasing resistance and decreasing the voltage of some individual cells within the battery. This causes the battery as a complete to appear to discharge quickly as those particular person cells discharge shortly and the voltage of the battery as a whole suddenly falls. The impact might be overcome by subjecting each cell of the battery to a number of deep charge/discharge cycles. This have to be done to the individual cells, not a multi-cell battery; in a battery, some cells may discharge earlier than others, resulting in those cells being subjected to a reverse charging present by the remaining cells, probably resulting in irreversible injury. Excessive temperatures can also scale back the charged voltage and the cost accepted by the cells.

Some rechargeable batteries can be damaged by repeated deep discharge. Batteries are composed of multiple comparable, however not similar, cells. Each cell has its personal cost capability. As the battery as a whole is being deeply discharged, the cell with the smallest capacity may attain zero charge and can "reverse charge" as the other cells proceed to power current by means of it. The resulting loss of capacity is commonly ascribed to the Memory Wave effect. Battery customers could try and keep away from the memory impact proper by fully discharging their battery packs. This apply is likely to cause more harm as one of many cells will likely be deep discharged. The harm is focused on the weakest cell, so that each additional full discharge will cause more and more injury 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 turns into a limiting consider total efficiency. Over time, this imbalance can lead to decreased capacity, shorter run times, and the potential for overcharging or overheating of the other cells, additional compromising the battery's safety and longevity.

All rechargeable batteries have a finite lifespan and can slowly lose storage capacity as they age attributable to secondary chemical reactions throughout the battery whether or not it's used or not. Some cells might fail sooner than others, however the effect is to scale back the voltage of the battery. Lithium-primarily based batteries have one of the longest idle lives of any development. Unfortunately the number of operational cycles remains to be quite low at approximately 400-1200 complete cost/discharge cycles. The lifetime of lithium batteries decreases at higher temperature and states of charge (SoC), whether or not used or not; most 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 introduced again to room temperature and recharged to 50% SoC once each six months or once per year. Bergveld, H.J.; Kruijt, W.S.; Notten, Peter H. L. (2002-09-30). Battery Management Programs: Design by Modelling. Linden, David; Reddy, Thomas B. (2002). Handbook Of Batteries (3rd ed.). New York: McGraw-Hill. p.