Understanding Memory Effect in Rechargeable Batteries

Memory effect denotes a temporary or permanent damage of capacity in a battery when it’s discharged. The usual understanding of the memory effect refers it to be causing due persistent under charging of a partially discharged cell. Researchers are not convinced and are neither unanimous on why this happens nor how to protect the capacity of batteries. Memory effect is more to do with the how and when of charging the battery instead of any specific fault in the battery itself. NiCd and NiMH batteries are the ones that are usually affected by these effects and more often than not the any disruption in NiCd is referred to as memory effect. Let’s look at how memory effect hampers NiCd batteries and how to work around these causes:

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  • One of the best bets to avoid the memory effect is to prevent the formation of large crystal cadmium. In this effect the slow charging is bad, as slow growth aids large crystal growth.
  • At the same time very high temperatures are not good as well, as the crystal growth thrives in very high temperatures. But over a course of time crystals will grow and one needs to be extra careful and instead replenish the material.
  • The need of the hour is a proper implementation of the battery charging and discharging cycle, which helps to blow off the large crystal cadmium and instead replace it into a form which is best for discharge.

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  • This though doesn’t give us the license to recharge the battery at every usage, this may cause more harm than good and can also reverse the cells causing the cells to die completely.
  • What can be instead done is to use the cells till maybe about 85-95% of the capacity of the cell, which means it is almost discharged and then at this stage one should go for a proper recharge.
  • Storing batteries properly goes a long way in counter fighting the memory effect. It is best to avoid leaving the batteries in hot, humid conditions such as a closed car. Ideal storage conditions should be a cool and dry place. Refrigerator is also a preferred place, but to keep them dry, batteries if stored in a refrigerator should be kept in a sealed bag along with a pack of silica gel. If you are planning to reuse batteries which have been storage it is always good to first charge them back fully before use.

Memory effect doesn’t necessarily affect the mobile phone batteries today, as these mobile phones are programmed to automatically switch a after about 90% of the battery usage, thus never getting completely discharged. Just leaving the phone to discharge and then charging it up will help get you more out of your mobile phone and will not infest it with memory effect.

Quite understandably memory effect can easily be circumvented in rechargeable batteries and considering the value for money it brings it is not wise to discard rechargeable batteries just to avoid memory effect.

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