What is NiCad battery memory effect?
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CHEAP INTERNATIONAL CALLSFor as long as rechargeable NiCad batteries have been available to the consumer, we have been warned about the dreaded ‘memory effect’. How important it is to periodically completely drain the battery of all power to eliminate the memory effect?
In Dan’s Quick Guide to Memory Effect he give a pretty good explanation as to why Nickel Cadmium rechargeable batteries should not be completely discharged and how doing so will shorten the lifespan of the cells in the battery pack. Until I read the section about ‘reversing a cell’ I did not realize that by completely draining the battery pack that the weaker cell will end up being ‘charged’ by the more powerful cells.
Dan’s article does not talk about what causes NiCad and NiMh batteries to eventually fail, dendrites. In an ideal world batteries would discharge and recharge at the same rate. When a battery pack is being recharged current is being run backwards through the cell to drive the chemical reaction in reverse. Ideally the material should deposit itself evenly across the plate. In reality, the material builds up in areas causing small bumps, over time these bumps grow because they are physically closer to the other plate and eventually a dendrite forms.
A dendrite is a thin filament of material through the separator material and allows the cell to short out. There are all kinds of theories and techniques for revitalizing a dead battery pack, some are fairly benign and others if not done right can result in an explosion of the battery pack.
Overall I agree with Dan’s explanation of memory effect and the myth surrounding it.
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