Do Lithium Batteries Expire if Not Used?
The answer is yes, lithium batteries can indeed “go bad” if left unused for a long time and stored improperly. This can lead to decreased battery capacity, increased internal resistance, deteriorated performance, and even complete malfunction.
What exactly causes this? And how can we prevent it from happening? Let’s take a closer look.
Cause of Damage
Generally speaking, lithium batteries have a long shelf life. However, lithium batteries will naturally discharge during storage, and their charge will gradually decrease if left unused for a long time. Even though the self-discharge rate of lithium batteries is usually low, if they are not charged for an extended period, their charge may drop to an excessively low level. Continuing to use or storing a lithium battery when its charge is too low can lead to over-discharge. This can damage the battery’s internal structure, affect its performance, and even render it unusable.
Improper storage conditions, such as temperature and humidity, can accelerate the self-discharge and internal chemical reactions that occur during long-term storage, leading to faster damage to the lithium battery.
If your lithium battery is equipped with a BMS (Battery Management System) and alarms, these devices monitor and intelligently manage the battery. Even then, storage can consume the battery’s charge, accelerating its discharge rate.
So how can we prevent this from happening? Let’s look at some relevant precautions.
Storage Precautions
Power
Maintaining 40%-60% charge is the optimal charge level for long-term storage of lithium batteries. Within this range, the positive and negative electrode materials are most stable, the internal side reaction rate is lowest, and aging is slowed down to the greatest extent. Never store a battery that is fully charged (>80%) or completely drained (<20%). Data shows that storing a fully charged battery for one month may cause a 3% capacity reduction, while storing it at 50% charge results in only a 0.5% capacity reduction.
Storage Environment
The ideal temperature for lithium batteries is between 15°C and 25°C. High temperatures act as a catalyst for battery aging; the higher the ambient temperature, the faster the internal chemical reactions and the faster the aging process. For example, the capacity loss after six months of storage at 45°C may be several times greater than that at 25°C.
Lithium batteries should be stored in a dry environment to prevent moisture and corrosion at the battery terminals or internal components.
Regular Maintenance
For lithium batteries that are not used for a long time, to prevent the charge from dropping to a dangerously low level, it is recommended to charge the battery every 3 to 6 months, then restore it to 40%-60% charge before storing it.
There are some things to note when charging lithium batteries. If you’re interested, you can click on the lithium battery charging tips to learn more.
Summary
In general, to prevent lithium batteries from deteriorating due to prolonged disuse, the core principles are a suitable storage environment and regular maintenance to keep them charged. Of course, there are many subcategories of lithium batteries; for specific details, please refer to the manufacturer’s instructions for use and storage requirements.