Memory effect

The memory effect is a phenomenon that reduces the capacity of batteries with incomplete loads. It occurs when a battery is charged without being completely discharged: crystals are created inside these batteries, because of a chemical reaction when the battery is heated, either by use or by poor loads. To prevent this, it is not necessary to wait until the battery is fully discharged before charging; it is enough that all loads are complete.

There are chargers in the market, which perform an equalization on the batteries; they charge very slowly, to charge the battery to its maximum real load.

Among the batteries affected by the memory effect are the nickel cadmium (NiCd) battery and, to a lesser extent, the nickel and metal hydride (NiMH) battery. On the contrary, lead and acid batteries or lithium-ion batteries are hardly affected by it.

Even in batteries with no memory effect, a complete discharge is recommended followed by a full charge from time to time. Lithium batteries are recommended monthly, if used regularly.

Lithium-polymer batteries (LiPo), for safety reasons, can not be discharged below a certain voltage, usually about 3 volts per cell (a cell being a physical unit called S, a battery may consist of 2 or 3 cells connected together in series), and the loading conditions are also delicate. However, they are the ones that store more energy with respect to their weight and are hardly affected by the memory effect.

There are other types of non-chemical batteries that do not show memory effect, such as inertial batteries or capacitors.

Another similar phenomenon that affects lithium ion batteries is the passivation that occurs when the battery is left unused for a long time or small charges are made. Complete loading and unloading solves this effect. Passivation is a thin film of lithium chloride (LiCl) on the surface of the anode (it is even beneficial because it prevents its self-discharge). It disappears as the battery is being used. If the passivation is excessive, the voltage may fall below the operating value, if the energy required at the beginning of operation is very large (passivation can be considered as an internal resistance of the battery), only then loads and discharges would be necessary. / p>

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