What Happens to a Laptop Battery Left Untouched for a Year
Pull an old laptop out of a closet after a year and the battery is either dead, swollen, or fine — and which one you get comes down almost entirely to what charge level it was sitting at when you put it away. Laptop battery long term storage isn’t complicated, but the two most common habits people fall into are close to the worst-case options: storing it fully charged, or storing it after it’s run all the way down to zero.
Why Full and Empty Are Both Bad Choices
A lithium-ion cell degrades fastest when it sits at high voltage for long stretches, which is exactly what happens when a laptop is stored at 100% and left alone. The chemical reactions that slowly eat away at capacity run faster the closer the cell sits to full. On the other end, a cell stored fully discharged can drift into a deep-discharge state over months of self-drain, and some lithium-ion protection circuits will refuse to recharge a cell that’s dropped below their safety threshold — which is usually what people mean when they say a battery is dead and won’t charge at all after long storage.
The middle ground works because it minimizes both problems at once. A battery sitting around 50% has enough voltage that the protection circuit stays happy, but not so much that the cell is under constant high-voltage stress. Apple’s own guidance for long-term device storage lands on the same number for exactly this reason.
| Storage charge | Risk after a year |
|---|---|
| 100% | Faster capacity loss from sustained high voltage |
| 50% | Lowest combined risk |
| 0% | Possible deep-discharge failure, may not recharge |
Temperature Matters Almost as Much
A battery stored at 50% in a hot attic will still degrade noticeably faster than one stored at 50% in a closet at room temperature. Heat accelerates the same internal reactions that voltage does, so the two compound each other — a fully charged battery left in a hot car for a summer is close to the worst combination you could pick. Cool, dry storage in the 50-70°F range is a reasonable target for anything sitting unused for months.
If you know a device is going into storage for longer than six months, it’s worth checking on it partway through and topping back up to roughly 50% if it’s drifted low, since self-discharge is slow but not zero. This is the same logic that applies to storing rechargeable batteries at home more generally — the chemistry doesn’t care whether it’s inside a laptop or a battery drawer. And if a battery comes out of storage swollen, unusually warm, or won’t hold any charge at all, that’s one of the signs a rechargeable battery needs replacing rather than a candidate for reviving. A swollen cell should go to an e-waste or battery recycling drop-off, not the trash, and never get pried open at home.
