What is Battery Memory Effect?

The battery memory effect is a phenomenon that occurs when a battery crystallizes internally during repeated charging and discharging. This effect is caused by repeated partial charging and incomplete discharging of the battery, which makes the battery seem to “remember” the previous state of charge, resulting in subsequent charging only to the level of the previous incomplete discharge, and thus unable to fully utilize its rated capacity.

Origin of Memory Effect

The memory effect was first observed in nickel-cadmium batteries used in satellites in the early 1960s when NASA used nickel-cadmium batteries extensively as the primary power source for various space missions. However, scientists found that these batteries showed significant degradation in performance and capacity after multiple partial discharges and recharges. Further experiments and observations showed that these batteries formed crystals on the surface of the electrodes after many incomplete discharges, thus limiting the electrochemical reaction capability of the batteries, a phenomenon that came to be known as the “memory effect”.

Principles and Impact of Memory Effect

The memory effect can be attributed to changes in the negative electrode or cadmium plate. During charging, cadmium hydroxide is converted to cadmium metal, and the deposited cadmium metal is in the form of small crystals. However, over time, these crystals will combine together to form larger crystals in high energy areas, and as the crystals become larger they may cause an increase in internal resistance, an increase in self-discharge, and even the electrode diaphragm may be punctured by the larger crystals resulting in a short-circuit, which reduces the capacity and impairs the performance of the battery.

In practice, this means shorter device usage time, more frequent charging, and even the risk of short-circuit, affecting user experience, battery life and safety. Especially in devices that require stable power for long periods of time, the memory effect can lead to unstable and unpredictable device performance.

Batteries Prone to Memory Effect

The memory effect occurs mainly in nickel-cadmium batteries. This effect is due to the fact that the negative electrode in the conventional process is sintered and the cadmium grains are coarse, so if the battery is not fully discharged, crystals will form in the undischarged part of the cell. The crystals weaken the conductivity of the material and therefore the voltage decreases as the crystal size increases. A similar phenomenon can be seen in nickel-metal hydride batteries, but to a lesser extent. This phenomenon is also known as the “ lazy battery effect”.

Solutions to Memory Effect

Although the battery memory effect cannot be completely eliminated, some methods can be taken to reduce its impact and prolong the life of the battery:

• Regular full discharge and recharge: Helps to restore unused capacity to the battery;
• Deep discharging and charging: activates the active substances in the battery and removes any crystallization that may be present;
• Regular maintenance: enables you to know the battery status in time and take relevant maintenance operations to prolong the battery life;
• Choosing the right type of battery: due to the difference in electrochemical characteristics, lithium iron phosphate batteries do not produce memory effect, so you can choose lithium iron phosphate batteries to replace them, so as to avoid the occurrence of memory effect.

Through the above content, it is hoped that readers can gain a better understanding of the battery memory effect and learn how to better deal with and solve the occurrence of memory effect, thereby achieving a better battery usage experience in daily life and work.