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Memory Effect

An effect observed in nickel-cadmium and nickel-metal hydride rechargeable batteries that causes them to hold less charge.

Memory effect, also known as battery effect, lazy battery effect, or battery memory, is an effect observed in nickel-cadmium and nickel-metal hydride rechargeable batteries that causes them to hold less charge. It describes the situation in which nickel-cadmium batteries gradually lose their maximum energy capacity if they are repeatedly recharged after being only partially discharged. The battery appears to "remember" the smaller capacity.

The term "memory" came from an aerospace nickel-cadmium application in which the cells were repeatedly discharged to 25% of available capacity (plus or minus 1%) by exacting computer control, then recharged to 100% capacity without overcharge. This long-term, repetitive cycle régime, with no provision for overcharge, resulted in a loss of capacity beyond the 25% discharge point. True memory cannot exist if any one of the following conditions holds:

  • batteries achieve full overcharge.
  • discharge is not exactly the same each cycle, within plus or minus 3%
  • discharge is to less than 1.0 volt per cell

True memory-effect is specific to sintered-plate nickel-cadmium cells, and is exceedingly difficult to reproduce, especially in lower ampere-hour cells. In one particular test program designed to induce the effect, none was found after more than 700 precisely-controlled charge/discharge cycles. In the program, spirally-wound one-ampere-hour cells were used. In a follow-up program, 20-ampere-hour aerospace-type cells were used on a similar test régime; memory effects were observed after a few hundred cycles.

Key Terms

battery effect
battery memory
charge
definition
discharge
effect
lazy battery effect
memory effect
nickel metal hydride rechargeable batteries
usage

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Memory Effect
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Last modified on September 18 2019
Content adapted from Wikipedia
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