Photo by magraphics @ 123RF.com
In the modern age of portable electronics, nothing seems to be more important than keeping your devices fully charged. Whether it is a cell phone, laptop, or tablet, consumer electronics have adopted lithium-ion and lithium-polymer batteries as a means of eliminating the cord. The problem is, even these advanced batteries seem to lose holding capacity over time.
Why do rechargeable batteries eventually die? Rechargeable batteries eventually die due to a breakdown in the chemical flow of charged ions. The anodes and cathodes that send and receive charged ions wear out over time, resulting in degraded ion flow and inefficient battery life.
Time has a way of causing wear and tear on all worldly objects, with lithium-ion and lithium-polymer batteries being no exception. The science shows that a rechargeable battery loses about 20 percent of its capacity for every 1,000 charge cycles, meaning that a few seconds of battery life are lost with each charge, giving most batteries a useful life of about three years.
Why Do Rechargeable Batteries Die or Expire?
Rechargeable batteries die and/or expire over time due to a chemical breakdown in the flow of ions. To better understand what causes this process, it is essential to understand the construction of a lithium-ion battery and how the charge and discharge process works.
This is the area where charged lithium atoms are stored. Lithium is a preferred material for portable batteries, thanks to its minimal size, which is smaller than all elements except hydrogen and helium; this allows for a very high storage of charge and voltage for unit volume and mass.
During a discharge cycle (when the device housing the lithium-ion battery is in use), an electron is removed from the lithium atom and left behind in the anode. The ions (charged atoms) move through a micro-permeable separator, traveling through an electrolyte in-route to the cathode.
The cathode is the opposite of an anode. Once the ions reach the cathode spent as a result of the electrical current they provided to the device, they recombine with an electron and become electrically neutral once again. By charging the battery, you are simply reversing the process and sending the atoms back to the anode in preparation for another discharge.
Why Rechargeable Batteries Degrade: A Hypothetical Model
Maybe the fancy, scientific words used to explain why rechargeable batteries break down do not make much sense to you, and you are still unsure as to the cause of the degradation process. Therefore, it can be helpful to use an example to help illustrate the process.
Step One: Set up a Hypothetical Model
For this illustration, you will need to imagine you are on a beach with two buckets, one bucket to represent the anode and one bucket to represent the cathode. You will also need 300 building blocks to represent the lithium atoms and ions. Place the buckets about 100 feet apart along the beach.
This whole hypothetical scenario, with the beach, buckets, and building blocks, can roughly be referred to as the “battery” for the purposes of this experiment.
Step Two: Fill the Buckets
Connect 200 of the building blocks and fit them into the near bucket representing the anode. These will represent the complete lithium atoms. Place the remaining 100 free building blocks in the far bucket that represents the cathode. These will represent the electrons that are waiting to attach to the lithium ions at the conclusion of electrical conduction.
Step Three: Perform the Ionization
In the anode bucket, disconnect the building block, leaving one “electron” behind in the anode bucket and pushing the free “ion” through the sand to the cathode bucket on the other end.
In this rudimentary example, the sand represents the electrolyte, or the conductor through which the “ion” travels on its path to the cathode. The enjoyment you get from playing with the “ion” would represent the electrical output in a real battery situation.
Step Four: Attach the Electron in the Cathode to the Ion
Once the “ion” has traveled through the “electrolyte,” attach it to an “electron” that is waiting in the cathode bucket. This turns the “ion” back into a full, electrically neutral lithium atom.
Step Five: Repeat the Process
Use the steps mentioned above to repeat the process of ionization in the anode, conduction through the electrolyte, and atomization in the cathode bucket for the remaining 99 lithium atoms.
When the cathode bucket is entirely full of 100 complete lithium atoms, your “battery” is officially dead and needs to be recharged, as there is no more opportunity to move charged ions through your sandy conductor.
Therefore, the charging process needs to occur, and the above steps need to be completed in reverse, sending the lithium atoms from the cathode back to the anode for a fresh run.
Step Six: Continue this Process Over Hundreds of Trials
Imagine, in this hypothetical experiment, that this process of discharging and charging your battery takes place over many, many trials. The following are a few of the breakdowns that can take in the process:
- The pegs and ports that connect your building blocks can get scratched and worn down by sand, making the process of ionization and recharging inefficient and causing some of the original atoms lose their usefulness.
- The buckets can get filled with a sand byproduct that is carried by the ionized building blocks, causing them to lose their ability to send and store completed building block atoms.
- Any weather elements, such as wind or water, may damage the system, causing inefficiencies or inadequacies in the process.
Through a combination of forces in the breakdown of this “charging” and “recharging” process, the buckets that were initially able to hold 100 complete building block atoms are now only able to handle a fraction of that total. This limits the amount of “enjoyment” you get when traveling the ionized block through the sand.
While overly simplistic and not 100 percent scaleable, this rudimentary experiment can help you better understand why rechargeable batteries lose life over time. As the repeated chemical flow of lithium ions degrades over time, the anodes and cathodes that house these lithium atoms lose their holding capacity, reducing the amount of time you get on a fully charged battery.
What to Do to Extend Your Rechargeable Battery Life
There is an old saying that Father Time has an undefeated record, meaning that even with the most concerted care, everything will come to the end of its useful life in due time.
Unfortunately, this is also the case for your rechargeable battery. No matter how well you care for it, it will eventually lose its ability to hold a charge. Even stored batteries that are never used can degrade due to time, so, generally, the most critical factor of the condition of a battery is its date of manufacture, as older batteries are likely to have a limited charge capacity.
However, while there is no way to slow time’s debilitating effects, there are several ways you can care for your battery to ensure that you maximize its useful life.
Do Not Completely Discharge Your Battery
There is a pervasive notion that the best way to ensure a long life for your rechargeable battery is to run it down all the way to zero percent and charge it all the way back to full charge. This theoretically ensures that the battery has a long memory and will be conditioned to operate for longer charge cycles.
The reason this idea is so prevalent is that it used to be the proper way to care for a rechargeable battery.
Without getting too technical regarding the science, older rechargeable batteries, such as those used in old remote control toys and portable power tools, used a nickel-cadmium composition, which would suffer from the memory effect.
This memory effect for older nickel-cadmium batteries means that if a battery were only using a small range of its capacity, it would become conditioned to only charge to that capacity. A brand new battery would quickly be reduced to a 50 percent capacity if that were all of the range it was using, so owners were instructed to use the battery until it died and then fully charge it.
However, while some laptops may still use nickel-cadmium technology, most modern rechargeable batteries, such as those used in smart devices, tablets, and even electric cars, use a lithium-ion or lithium-polymer composition.
As lithium-ion and lithium-polymer batteries do not suffer from memory effect, they should not be completely discharged. Deep discharges can cause the metal plating used in the anode and cathode to short circuit in some cases, leading to more rapid degradation.
Recharging your lithium-ion battery after 20% to 30% of use helps you increase the chances of extending your battery’s life.
The one exception is that once a month, it is recommended to let your battery run down to about 5% capacity before recharging. This allows the battery to re-calibrate its self-assessment, which gives your device the chance to provide you with a more accurate reading of how much time is left on the charge.
Avoid Charging to 100 Percent Capacity
Just as completely discharging a lithium-ion battery is not recommended, it is equally inadvisable to charge your battery to 100 percent capacity consistently.
Shallow charges and discharges put less stress on the battery, which allows them to operate more efficiently over time. In addition, if your battery reaches a 100 percent charge, it is advisable to unplug it. This means the favorite practice of plugging your phone in at night and leaving it a 100 percent charge while sleeping may not be the best idea for battery life.
While a lithium-ion battery has safeguards that will prevent it from exploding if it is charged to 100 percent and left plugged in, studies show that modern batteries age faster if they are always plugged in while already charged to 100 percent.
If you are super serious about getting the most life out of your rechargeable battery, there are specialized chargers that can be programmed to switch off before the battery reaches a 100 percent charge.
Keep Your Battery at Room Temperature
While lithium-ion batteries do perform much better and are less affected by extreme temperatures than nickel-cadmium ones, you can help extend your battery life by keeping your battery at room temperature, which is generally around 70°F, plus or minus a few degrees.
One of the worst things for a lithium-ion battery is having it fully charged, plugged in, and left in extremely high temperatures. Therefore, make sure that you do not leave it charging in your car on especially hot summer days when the vehicle is not on, and the air conditioning is not running.
In addition, when attempting to charge a battery below freezing, you run the risk of causing short circuits and metal plating in the anode and cathode, causing it to become unstable.
Store the Battery Safely
If you have a cell phone or other electronic device, there is probably not much need to store your lithium-ion battery, as these devices are likely to always be in use. However, if you find yourself in a situation where storing your battery is necessary, then you will want to save it at about 40 percent capacity in a cool place.
Oxidation, which is one of the leading causes of battery degradation, occurs quicker at fuller charge levels and in warmer, more humid conditions. Hence, a partial charge and cool conditions are necessary if the battery is going to sit for a while.
Signs That Your Rechargeable Battery May Be Failing
There are several warning signs that your rechargeable battery may be nearing the end of its useful life. While the symptoms will not be the same for every battery, if you notice one or more of the following conditions and are dependent on your battery for a critical function, it may be time to get it immediately replaced.
Shortened Battery Life
This one is pretty obvious, but it is definitely the most common symptom of a dying rechargeable battery.
For smartphone owners, everyone knows the frustrating feeling of going out on the town with a fully charged phone, making a call, and sending a couple of texts, and then looking down to see that your phone is under 50 percent capacity.
Most modern devices have functions that allow you to check battery health. If you go into the settings and see that the battery is at less than 80 percent of factory capacity, it is time for a replacement. If not, the fact that it can no longer hold a charge for very long is a strong sign in and of itself.
Inaccurate Charge Reading
If your battery gauge displays that you have a significant amount of power remaining and then it suddenly dies, it is a likely symptom of a degraded battery.
Lithium-ion batteries differ from nickel-cadmium ones in that they power your device at full capacity until the battery runs out of juice. At this point, they shut completely off, whereas nickel-cadmium batteries would cause a whining or slower function in your device as the battery slowly reached the end of its charge.
Therefore, a lithium-ion battery that shuts off when displaying a sufficient charge level is most likely due to it no longer being able to run an adequate self-assessment on a battery that has such a degraded charge capacity.
Battery Not Reacting to Charger
In some cases, a degraded battery will not react to a charging source. While you should definitely check to make sure that the outlet you are using is functional and that there are no issues with the charging port, batteries that do not react to a power source are likely degraded to the point of no longer being able to hold a charge.
What to Do if Your Rechargeable Battery Dies
It is obvious that if a rechargeable battery dies, it needs to be replaced, as a battery that no longer holds a charge is of no use and needs to be recycled or properly disposed of. However, you do need to be a little bit careful before simply switching out the old with the new, as there are some caveats that can cause expensive functionality issues.
First, lithium-ion batteries are not necessarily cheap, so you will want to make sure that replacing the battery is not more expensive than replacing the device itself.
The other important consideration is compatibility. Some after-market batteries are cheaper than those designed by a name brand manufacturer, but after-market batteries may not work with all devices.
This is especially true with smartphones that like to ensure brand loyalty by making their devices compatible with their specific batteries. While some government regulations eyeing sustainability have been imposed to prevent this practice, you want to make sure to do your research before switching out batteries to avoid using a battery that does not work for you.
One thought on “Why Rechargeable Batteries Eventually Die (and What to Do)”
Unfortunately, many mfrs tell their lithium-device customers to do exactly the opposite of your suggestions: DO cycle down to 0% then up to 100% 3-5 times!!! Ignorance or planned obsolescence? (one mfr’s 2021 lithium-based device costs $180, but a new battery costs $70!!!) I have seen multiple customer reviews about how great the relevant device is, but, the lithium battery stinks! Why don’t mfrs include some intelligence in their devices and chargers to mitigate these issues, perhaps by so simple a thing as keeping track of the specific battery, when it was used, when it should be charged (i.e., turn off before it hits zero), charge it, randomly to 90-100%, etc.