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What is Memory Effect?

by: cellular-link( 16878Feedback score is 10,000 to 24,999)
0 out of 1 people found this guide helpful.
Guide viewed: 127 times Tags: memory effect | battery capacity | voltage | discharge


Memory effect, also known as lazy battery effect, is an effect observed in some rechargeable batteries that causes them to hold less charge. In its original meaning it describes one very specific situation in which certain NiCd batteries gradually lose their maximum energy capacity if they are repeatedly recharged after being only partially discharged. Today the term is commonly applied to almost any case in which a battery appears to hold less charge than was expected.

Other problems described as memory effect

  • Voltage depression due to over-charging
In the case of voltage depression, the peak voltage of the battery drops more quickly than normal as it is used, even though the total energy remains almost the same. In modern electronic equipment that monitors the voltage to indicate battery charge, the battery appears to be draining very quickly and therefore about to run out of energy. To the user it appears the battery is not holding its full charge, which seems similar to memory effect. This is a common problem with high-load devices such as digital cameras. Voltage depression is caused by 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 lowering the voltage of some individual cells in the battery. This results in a seemingly rapid discharge as those individual cells discharge quickly and the voltage of the battery as a whole suddenly falls. This effect is very common, as consumer trickle chargers typically overcharge.
  • 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 described as memory effect.
  • Age and use
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. All rechargeable batteries have a finite number of charge/discharge cycles and will lose a very small amount of storage capacity during each cycle. Typically, rechargeable batteries are rated for hundreds or thousands of cycles.



Guide ID: 10000000006212595Guide created: 03/15/08 (updated 05/06/08)

 
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