Best Battery Percentage for Long-Term Phone Storage

If a phone is going in a drawer for weeks or months, the number to charge it to before you put it away is 50%, not 100% and not 0%. Apple and Samsung both say so directly, and the reason comes down to simple lithium-ion chemistry: a battery left fully charged or fully drained for a long stretch degrades faster than one parked in the middle.

This is a different question from the daily 80% charging limit some phones now offer. That setting is about slowing cycle wear on a phone you use every day. Storage charge is about a phone that will not be touched, sometimes for months at a time: an old phone kept as a backup, a second device, a work phone between jobs.

What Apple and Samsung actually say

Apple's own guidance is direct: "Do not fully charge or fully discharge your device's battery, charge it to around 50%." If the phone stays in storage longer than six months, Apple says to top it back up to 50% every six months. Apple also specifies a storage environment under 90°F (32°C).

Samsung's guidance lands in almost the same place: charge a Galaxy device to 50-70% before long-term storage, and recharge it once every three to six months. Samsung's stated reason is that "battery decline may accelerate if a device is left with a depleted battery for a long period of time."

Neither company frames this as a suggestion. Both treat storing a phone at 100% or at 0% as a real cause of measurable battery decline, not a minor inconvenience.

The actual numbers behind the advice

Battery University's testing shows why the 50% figure holds up. At room temperature (25°C), a lithium-ion cell stored at 40% charge retains about 96% of its capacity after a year. The same cell stored at a full charge retains only around 80% over the same year, a real gap driven purely by how full the battery sat while it wasn't being used.

Researchers at Chalmers University of Technology in Sweden found an even larger effect studying the same lithium-ion chemistry in electric vehicle batteries: holding a cell at 50% state of charge, instead of higher, extended its usable lifetime by 44-130%. That study was run on vehicle-scale batteries rather than phone cells, so the exact percentage will not transfer one-to-one to a phone, but it is the same underlying chemistry, and it points the same direction as Apple's and Samsung's phone-specific advice.

Why the middle of the charge range is easier on the battery

A lithium-ion battery ages fastest at the top and bottom of its voltage range. Sitting near full charge keeps the cell under high voltage stress with nothing drawing current off it, which is the condition that degrades capacity fastest over time. Sitting at empty risks a deep discharge that some cells cannot fully recover from. The middle of the range avoids both problems, which is exactly what Apple's and Samsung's numbers describe without spelling out the chemistry behind them. The same high-voltage stress is what drives up cycle counts on a phone you use daily; see iPhone cycle count explained for how that adds up over time.

What this does not apply to

This is a storage rule, not a daily charging rule. A phone you use every day should not be deliberately kept at 50% between charges just because storage batteries like that number. The 80% charging limit some phones offer is built for daily use, where the phone still needs to reach a workable charge each morning; storage charge only matters once the phone stops being used at all. The two settings solve different problems and neither substitutes for the other.

FAQ

What percentage should you store a phone at long-term?

Around 50%. Apple recommends roughly 50%, and Samsung recommends 50-70%. Both companies say to avoid storing a phone fully charged or fully drained.

Is it bad to store a phone at 100%?

Yes, measurably. Battery University's testing found a lithium-ion cell stored at full charge for a year retained around 80% of its original capacity, versus about 96% for one stored at 40%.

Is it bad to store a phone completely dead?

Yes. Apple and Samsung both warn that a fully depleted battery left in storage can drop into a deep discharge state, which can leave it unable to hold a charge normally again.

How often should you charge a phone in storage?

Apple recommends topping a stored device back up to 50% every six months. Samsung recommends recharging every three to six months. Either interval prevents the battery from drifting down into a deep discharge over a long storage period.

Does this apply to an old phone kept as a backup?

Yes. A backup or spare phone sitting in a drawer is exactly the case this guidance is written for. If you expect to grab it in an emergency, storing it around 50% and recharging it every few months keeps it in better condition than leaving it plugged in at 100% or letting it sit until it dies, and it slows the same year-by-year decline covered in how iPhone battery health declines over time.

Is a storage charge the same as an 80% daily charging limit?

No. A daily charging limit slows cycle wear on a phone you still use every day. Storage charge is for a phone that will not be touched for weeks or months. They address different situations and are not interchangeable.

If the phone you're storing is the only spare you have and your main phone dies out on a long day away from an outlet, that's a different problem than storage, and it's the one a rental network like Brick exists to solve: grab a powerbank at a station near you, charge up, return it anywhere on the network.