You have a spare battery or an old device sitting in a drawer. This makes you wonder if it will still work months or years from now, or if it will be completely dead.
A lithium-ion battery loses about 2-5% of its charge per month due to self-discharge. More importantly, its long-term health depends on its storage charge level and temperature. Stored properly, it can last for years; stored improperly, it can be permanently damaged in months.
At KKLIPO, our entire business is built on maximizing battery performance and lifespan. We know that how a battery is stored is just as important as how it is used. Even when a battery is not connected to anything, chemical reactions are still happening inside. Understanding and managing these reactions is the key to preserving your battery's health for the long term.
What Happens to a Battery When It's Just Sitting There?
You assume a battery only drains when it's being used. This leads you to store fully charged or empty batteries, unknowingly causing permanent damage and shortening their lifespan.
Even when idle, a battery experiences two things: self-discharge (a slow loss of its current charge) and capacity degradation (a permanent loss of its maximum energy-holding ability). The rate of both is heavily influenced by temperature and its storage charge level.
It's crucial to understand these two separate but related processes. One affects the battery's immediate readiness, while the other affects its fundamental health.
Self-Discharge: The Slow Leak
Think of self-discharge as a tiny, invisible leak in your battery's "tank." All batteries have it, but lithium-ion batteries are quite good, losing only a few percent each month at room temperature. However, this rate increases dramatically with heat. A battery left in a hot car will self-discharge much faster than one in a cool drawer. So, a fully charged battery left alone for a year could be completely empty, but that's not the biggest problem.
Capacity Degradation: The Real Killer
This is the permanent and irreversible loss of the battery's ability to hold a charge. It’s like the battery's tank is slowly shrinking over time. This aging process happens no matter what, but you can speed it up or slow it down dramatically. The two biggest factors that accelerate this aging process are temperature and the State of Charge (SoC) during storage. High temperatures and storing a battery at 100% or 0% are the fastest ways to kill it.
What is the Best Way to Store a Lithium-Ion Battery?
You just finished a project and won't need your drone for a few months. You fully charge the batteries so they are ready to go next time, thinking you're being prepared.
Never store a lithium-ion battery at 100% or 0% charge. The ideal state for long-term storage is around 50% charge (storage charge), kept in a cool, dry place. This minimizes chemical stress inside the battery and dramatically slows down the aging process.
The voltage of a lithium battery directly relates to its chemical stress. At 100% charge, the internal components are under high stress, which accelerates the breakdown of the electrolyte and causes capacity loss. At 0% charge, the voltage can drop so low that it triggers a protective circuit cutoff or, worse, causes permanent internal damage, making the battery unchargeable.
We design our drone batteries to withstand tough conditions, but the laws of chemistry apply to all lithium-ion cells. Following the "50% rule" is the single most important thing you can do to protect your investment.
Your Long-Term Storage Checklist:
- Charge/Discharge to 50%: Most smart chargers have a dedicated "Storage" function that does this automatically. For a standard LiPo, this is around 3.8V per cell.
- Find a Cool, Dry Place: A closet at room temperature is great. Avoid attics, garages, or leaving batteries in a car, where temperatures can swing wildly.
- Check Periodically: If you are storing for more than six months, it's a good idea to check the voltage every few months. If it has dropped significantly, top it back up to the storage level.
| Storage Condition | Impact on Battery Health |
|---|---|
| 100% Charge + High Temp | Worst Case: Rapid, permanent capacity loss. |
| 0% Charge (Empty) | Very Bad: Risk of over-discharge and permanent damage. |
| 100% Charge + Cool Temp | Bad: Still causes accelerated aging, just slower. |
| 50% Charge + Cool Temp | Best Case: Minimizes aging and preserves battery life. |
How Does This Apply to My Everyday Devices?
You have an old laptop and a spare phone in a drawer. You're not sure if they'll turn on, and if they do, whether the battery will last more than five minutes.
The same rules apply. A device stored for a year at full charge will have a noticeably weaker battery. A device stored empty may never turn on again. Storing devices at ~50% charge is the best practice for preserving their battery life.
Think about the battery inside any electronic device you own—from your phone and laptop to your high-performance drone batteries. They are all based on the same lithium-ion chemistry.
If you buy a new device and don't plan to use it right away, don't charge it to 100%. Most new electronics ship from the factory at an ideal storage charge for this very reason. If you have an old device you want to preserve, charge it to 50% and turn it off. Check on it once or twice a year to ensure the charge hasn't dropped too low.
This simple habit can be the difference between having a usable backup device in a year and having an electronic paperweight. It ensures that when you need that device, the battery is not only charged but also healthy.
Conclusion
A lithium battery loses charge slowly over time, but its long-term health depends on storage conditions. For maximum life, store it at 50% charge in a cool place, not full or empty.