What is Battery Memory Effect?

In our daily lives, we often notice that batteries don’t last as long as expected, even when they are relatively new. This phenomenon may be due to the “memory effect” The memory effect was identified in the 1990s, and it is not a good thing for batteries. It reduces the battery’s capacity, shortens its lifespan, and can even lead to early battery failure. Will the 18650 Li-ion batteries we usually use be affected? By understanding the memory effect in more detail, we can learn to better care for batteries and extend their life.

Overview of Battery Memory Effect

The memory effect typically occurs in rechargeable batteries, especially when they undergo incomplete charge and discharge cycles. This phenomenon makes the battery “remember” the previous discharge state, leading to a reduction in capacity and the inability to fully discharge. It’s important to note that non-rechargeable batteries like carbon-zinc or alkaline batteries do not experience memory effects.

How Memory Effect Impacts Performance

The memory effect can significantly affect a battery’s performance over time. The battery gradually loses its maximum capacity, meaning it delivers less energy after each full charge. This shortens its run time and reduces its overall effectiveness until the battery reaches the end of its life.

Causes of Battery Memory Effect

The memory effect primarily occurs due to incomplete charge and discharge cycles. When batteries are regularly charged without fully discharging, they “remember” this smaller capacity range and can no longer utilize their full capacity. This effect is most commonly seen in Nickel-Cadmium (Ni-Cd) and some Nickel-Metal Hydride (Ni-MH) batteries.

Which Batteries Are Affected by Memory Effect?

Memory effect typically affects Nickel-Cadmium (Ni-Cd) and some Nickel-Metal Hydride (Ni-MH) batteries. These types of batteries, when charged without fully discharging, gradually lose their maximum capacity. However, Lithium-Ion (Li-ion) and Lithium Iron Phosphate (LFP) batteries are less prone to memory effects due to their unique chemical properties, which make them less sensitive to partial charging and discharging.

Do Lithium-Ion Batteries Have Memory Effect?

It is widely believed that lithium-ion batteries do not have memory effects. However, some studies have shown that LiFePO4 lithium-ion batteries may exhibit slight memory effects. Although this memory effect is relatively minor, it can affect the accuracy of State of Charge (SOC) estimation, particularly after partial charge and discharge cycles. This phenomenon may appear as small “memory” traces in the battery’s voltage curve. While the memory effect in lithium-ion batteries is not as significant as in Ni-Cd and Ni-MH batteries, it can still occur in specific chemical compositions.

How to Prevent Battery Memory Effect?

For batteries prone to memory effects, such as Ni-Cd and Ni-MH, the best preventive measure is to perform regular complete charge and discharge cycles. This helps reduce the impact of memory effect. For lithium-ion batteries, the best practice is to keep the charge between 20%-80%, avoiding deep discharge and overcharging, which can extend the overall battery lifespan.

Strategies to Mitigate Battery Memory Effect

Different types of batteries require different strategies to mitigate the memory effect. For Nickel-Cadmium (Ni-Cd) and Nickel-Metal Hydride (Ni-MH) batteries, regular complete charge and discharge cycles can help preserve maximum capacity and reduce the memory effect. For Lithium-Ion (Li-ion) and Lithium Iron Phosphate (LFP) batteries, which experience a much lower memory effect, the best practice is to keep the charge level between 20%-80% and avoid deep discharges. Additionally, all types of batteries should avoid extreme temperatures to prolong their lifespan.

How to Fix Battery Memory Effect?

Battery memory effect can be partially corrected through multiple complete charge and discharge cycles. This is especially effective for Ni-Cd and Ni-MH batteries that have not been fully discharged for a long time. By performing deep discharge and charging repeatedly, it may be possible to restore part of the lost capacity. However, this method is not recommended for lithium-ion batteries since frequent deep discharging can damage them. For lithium batteries, maintaining good charging habits is more important than trying to fix memory effects. More about tips for extending the life of your lithium batteries.

Conclusion

Although lithium-ion batteries may exhibit a slight memory effect after a partial charge/discharge cycle, it is much less noticeable than in Ni-MH batteries. This mild memory effect does not significantly impact the performance of lithium-ion batteries. Users need not worry about its effect on day-to-day use, as lithium-ion batteries continue to provide reliable and stable performance.