Do Lithium Batteries Have a Charge Memory?
While a couple of types of rechargeable batteries have a charge memory, lithium-ion (or li-ion) batteries don’t. Even though li-ion battery performance isn’t affected by charge memory, it can be affected by other problems which are usually caused by misuse or use in harsh conditions. Ironically, many of these problems can mimic the signs of charge memory. The good news is that many of these problems, as well as the effects of charge memory itself, are preventable.
What is “Charge Memory?”
Charge memory, also known as the memory effect, is a phenomenon in which a rechargeable battery “remembers” its typical pattern of charging and discharging. This happens when a battery is consistently drained to approximately the same level of partial discharge, and rarely fully discharged.
For example, if only 50% of a battery’s charge is ever used, eventually the battery will start to “remember” the shortened life cycle. What was originally only 50% of the battery’s charge essentially becomes 100%, since the user won’t be able to discharge the battery past that point.
Once a battery has developed a charge memory, you may notice the following effects.
Reduced capacity
As explained above, a battery with a charge memory has lost the ability to fully discharge. This means that no matter how well you take care of the battery after it’s developed a memory effect, it won’t be able to power your devices as long as it’s meant to.
More frequent charges
A battery with reduced capacity will have to be charged more frequently, which can be both inconvenient and frustrating.
Shortened lifespan
Each type of rechargeable battery is designed to last for a certain number of recharge cycles, and can last for years if they’re used properly. However, if a battery is being drained and recharged more frequently than expected due to the memory effect, this will result in a shortened lifespan.
Types of Batteries that Have a Charge Memory
Even though lithium-ion batteries don’t have a charge memory, other commonly used rechargeable batteries do.
- Nickel-metal hydride (NiMH) batteries are most likely to develop a charge memory if they aren’t completely discharged before each recharge. Fortunately, modern improvements in NiMH battery design have made this problem less common. That being said, it’s best to fully discharge NiMH batteries from time to time; this prevents a charge memory from developing.
- Nickel-cadmium (NiCd) batteries are more likely than NiMH batteries to have a charge memory due to their internal chemistry. If these batteries go for too long without a full discharge, the crystalline structure of the cadmium plates changes, resulting in a charge memory.
Lead-acid batteries are another popular type of rechargeable battery, and while they are susceptible to reduced performance under certain circumstances, they don’t experience charge memory. Single-use batteries, such as alkaline and zinc-carbon batteries, don’t have a charge memory because once the original charge is used up, they can’t be recharged again.
Battery Memory Effect vs. Other Issues
Batteries with a memory effect will exhibit specific issues, mainly related to reduced capacity. These issues are because of changes that happen within the battery’s internal chemistry, and are usually reversible by taking the right steps. If an NiMH or NiCd battery has developed a charge memory, this can often be reversed by several cycles of deeply discharging, then fully charging.
While charge memory is limited to just two types of rechargeable batteries, other problems (such as overheating or sub-par performance) can happen to most types of rechargeable batteries.
- Overheating usually happens when a battery is being discharged too quickly, or when it’s in an environment that’s too warm (including pockets). The solution is simple: don’t overload the capacity of your rechargeable batteries, and as much as possible, keep them in cool, well-ventilated environments. This won’t always be possible; for example, electric vehicles are often used or parked in broad sunlight, and generally can’t be stored in an air-conditioned space. However, the voltage output and temperature of smaller devices such as smartphones, laptops, or battery-powered tools can be controlled much more easily.
- Decreased performance in a rechargeable battery can stem from all kinds of problems, from use in extreme temperatures to old age. It usually consists of either decreased voltage output, or the need for more frequent charges (or both). If a li-ion battery is experiencing these issues, it’s probably an indication of internal damage. The battery could still be functional for quite a while if it’s properly used and stored, but it probably won’t perform as intended.
How to Prolong Li-ion Batteries
Even though lithium-ion batteries aren’t susceptible to the memory effect, they can still experience other issues. Not all of them are reversible, but most of them are preventable. If you want to prolong the lifespan of your li-ion batteries, here are a few useful tips to follow:
Avoid extreme temperatures
The performance of li-ion batteries can be affected by temperatures that are either too low or too high (below 32 degrees, or above 90 degrees). This applies regardless of whether they’re being used or stored. To minimize the problem, try to be aware of when your devices are at risk of freezing or overheating, and take steps to normalize the temperature.
Store Li-ion batteries properly
Lithium-ion batteries should ideally be stored at around 50% charge; this is the sweet spot for the internal voltage of the cell, and is the reason why we ship our batteries at around 60% charge. Since a small percentage of the charge will be lost each month due to self-discharge, it’s recommended to top the batteries back up to 50% every six months or so if not in use. Storing at charges close to 0% or 100% isn’t recommended, as this won’t keep the cells as healthy over the long term.
Storage conditions should be dry, and the battery terminals shouldn’t be allowed to touch.
Follow charging best practices
One of the most important things to avoid when charging li-ion batteries is overcharging them. Habitual overcharging can significantly shorten the lifespan of li-ion batteries, so it’s recommended not to charge overnight. Maintaining a charge level between 20% and 80% is ideal, but not always possible. Even so, avoiding chronic overcharging will still have long-term benefits. Paleblue batteries come with a trickle-charge feature that prevents overcharging, so they aren’t affected if they’re left in the charger for too long.
Charging in near-freezing temperatures is very hard on lithium-ion batteries, and charging at temperatures below 32 degrees can permanently damage their internal chemistry. If you’re planning on using li-ion batteries in extreme cold, it’s better to bring along an extra set than to plan on recharging the same set.