Yes, lithium batteries lose charge when not in use, but the rate is slow compared to most other battery types. A typical lithium-ion battery loses about 1.5% to 2% of its charge per month just sitting on a shelf at room temperature. That means a fully charged battery left untouched for six months would still have roughly 90% of its charge remaining.
That said, the real-world number you experience can be much higher than the battery’s internal loss alone. The device the battery sits in, the temperature where you store it, and how full it was when you put it away all play a role.
Why Lithium Batteries Lose Charge on Their Own
Every battery slowly loses energy through internal chemical reactions, even with nothing connected to it. This is called self-discharge, and it happens because the materials inside the battery are never perfectly stable. Small amounts of the electrolyte (the liquid that shuttles charge between the two ends of the battery) break down over time. A protective film that forms on the battery’s internal surfaces during its first few charges also gradually thickens, consuming a tiny bit of stored energy in the process.
Water contamination, even at trace levels, accelerates these reactions. Manufacturing processes work hard to keep moisture out, but no battery is perfectly sealed forever. The chemical degradation from water is one reason older batteries self-discharge faster than new ones.
Device Drain vs. Battery Drain
The 1.5% to 2% monthly figure describes what happens inside the bare battery cell. In practice, the device around the battery often draws far more power than the battery loses on its own. Phones check for notifications. Laptops maintain memory. Power tools with Bluetooth connectivity keep their radios alive. Even the battery management system (BMS), the small circuit board built into most lithium battery packs, consumes a small amount of power continuously.
For small devices, the BMS draw is negligible. A typical four-cell battery pack’s management circuit pulls around 50 microamps, which is essentially nothing. But larger systems with external contactors or relays can draw meaningfully more. In one common solar battery setup, the relay alone accounts for roughly 13% drain per month on a 400-amp-hour bank. That dwarfs the battery’s own self-discharge.
If your device seems to lose charge much faster than 2% per month while “off,” the culprit is almost certainly the electronics, not the battery itself. Turning a device fully off (not just to sleep mode) or disconnecting the battery when storing something long-term makes a significant difference.
How Temperature Changes the Equation
Heat speeds up the chemical reactions that cause self-discharge. A lithium battery stored in a hot garage or car will lose charge noticeably faster than one kept in a climate-controlled room. As a rough guide, self-discharge roughly doubles for every 10°C (18°F) increase in temperature above room temperature.
Cold temperatures, on the other hand, slow self-discharge but temporarily reduce how much energy the battery can deliver. At 0°C (32°F), a lithium-ion energy cell can only access about 83% of its rated capacity. At -20°C (-4°F), that drops to roughly 53%. This isn’t permanent damage. The full capacity returns once the battery warms up. But it means a cold battery that reads “50%” might behave like it’s nearly dead until it comes back to room temperature.
The ideal storage temperature for lithium batteries is cool but not freezing, somewhere around 10°C to 15°C (50°F to 59°F).
Long-Term Storage: Years, Not Months
Lithium batteries hold up remarkably well over long periods when stored properly. A study published in the Journal of Power Sources tested 100 commercial lithium iron phosphate cells after ten years of uninterrupted shelf storage at about 50% charge and 6°C. Every single cell retained between 96% and 98% of its original capacity. Resistance changes were negligible. When researchers then cycled the cells for ten additional months, they performed just like fresh batteries with no extra precautions needed.
That’s an unusually favorable scenario (cool temperature, moderate charge level, a chemistry known for stability), but it illustrates the point: lithium batteries don’t just quietly die on the shelf. Stored correctly, they last for years.
For more common lithium-ion chemistries like those in phones and laptops, you can generally expect a battery stored at room temperature and 50% charge to remain usable for two to three years, though it will gradually lose some total capacity over that time due to calendar aging, a separate process from self-discharge.
Best Storage Practices
How you store a lithium battery matters more than most people realize. A few choices make the difference between pulling a battery out of storage ready to go and finding one that’s degraded or dead.
- Charge level: Store batteries at around 40% to 60% charge. A fully charged lithium battery ages faster because higher voltage stresses the internal materials. A nearly empty one risks dropping below safe voltage levels during months of self-discharge.
- Temperature: Keep batteries in a cool, dry place. A basement shelf or interior closet is better than a garage or attic. Avoid freezing temperatures for batteries in devices, since condensation can form when they warm back up.
- Disconnect from devices: If you’re storing a laptop, power tool, or other device for months, remove the battery if possible. The device’s standby draw will flatten the battery far faster than self-discharge alone.
- Check every few months: For storage lasting six months or longer, check the charge level periodically and top it back up to around 50% if it has dropped significantly. This prevents the battery from ever reaching dangerously low voltage.
When Low Charge Becomes Permanent Damage
The real risk of self-discharge over very long periods isn’t the lost charge itself. It’s that the voltage can eventually drop low enough to cause irreversible damage. Most lithium-ion cells have a minimum safe voltage around 2.5 volts (the nominal full charge is around 4.2 volts). Below that threshold, copper from the internal current collector can dissolve and form tiny metallic deposits inside the cell. These deposits can create internal short circuits, permanently reducing capacity or making the battery unsafe to recharge.
Most battery packs have a management circuit that cuts off discharge before voltage drops this low. But if a pack sits long enough that even the BMS circuit drains the cells below the cutoff, or if the cells self-discharge past that point over years of neglect, the pack may refuse to charge at all. At that point, the battery is effectively dead.
This is rare with normal storage timelines. At 2% per month, it would take well over a year for a half-charged battery to approach dangerous voltage levels from self-discharge alone. But combined with parasitic drain from electronics, a forgotten device in a hot closet can get there faster than you’d expect.