ShelfYears

Do batteries expire?

They do, and the year printed on the pack is a shelf life, not a runtime — Energizer rates a cylindrical alkaline at 5 to 10 years in the packet and Duracell guarantees Coppertop for 10, but neither number says anything about how long a cell will run the flashlight you are holding.

Updated

Batteries (alkaline, lithium, rechargeable)
Sealed
5–10 years (alkaline)
Opened
The device sets the clock
SELF-DISCHARGE & SEAL AGING
Equipment damage

Sealed: 5–10 years (alkaline) Tier 1

Energizer's figures, at room temperature (70°F / 21°C): cylindrical alkaline 5 to 10 years, carbon zinc 3 to 5, lithium cylindrical 10 to 15 — and prolonged storage at elevated temperatures will shorten storage life. Duracell puts a 10-year storage guarantee on Coppertop and 5 years on the 9-volt. Two makers, two answers for the same AA: that spread is information, and the packet date is the tiebreak.

By manufacturer — the disagreement is information
Brand Sealed window
Energizer alkaline, cylindrical 5–10 years
Duracell Coppertop alkaline 10 years guaranteed
Duracell Coppertop 9-volt 5 years guaranteed
Energizer lithium, cylindrical 10–15 years
Carbon zinc 3–5 years
Duracell NiMH rechargeable Rated in recharges, not years

After opening: The device sets the clock Tier 1

A loose cell out of its packet is still on the shelf clock — Energizer's years assume room temperature and moderate humidity either way. A cell inside a device is on a different clock entirely: Energizer says the most important factor in how long it lasts there is the rate at which the device consumes power, so a camera empties what a clock would have run for a year. That is a runtime question and no shelf life answers it. Duracell's rule is the practical one — take the cells out of anything you do not expect to use for several months.

How to tell it's gone off

  • Read the best-before year printed on the cell or the pack — the makers print this plainly, in years, not in code.
  • White or blue-green crust on the ends of a cell, or inside a device's battery compartment.
  • A cell that looks swollen, or whose label has lifted, split or discolored.
  • Cells that stick in the compartment: corrosion has bonded them to the contacts.
  • Rechargeables that come off the charger and go flat within days have lost capacity, not charge.

If you use it anyway

Equipment damage

The failure that costs you something happens in the device, not in the packet. Energizer says alkaline cells typically will not leak in normal storage but that the risk rises sharply once one has been run deeply flat or held in heat, and Duracell's care list says to take cells out as soon as they are depleted, because some devices keep drawing power from exhausted cells and that can make them leak. What leaks is extremely caustic and it corrodes the contacts of whatever it is sitting in. Energizer's own guarantee offers to repair or replace a device damaged by its cells — that is how the makers rate the risk themselves.

Why it goes off — SELF-DISCHARGE & SEAL AGING

A cell is a slow chemical reaction with a lid on it, and even in the packet it quietly spends a little of itself. Heat is what accelerates that, which is why a garage shelf is a worse home than a kitchen drawer. The seal is the other half of the story: Energizer says alkaline cells typically will not leak in normal storage, but that the risk rises sharply once a cell has been deeply discharged or held at high temperature — and what comes out is extremely caustic.

Every page here commits to one of four states — Harmless · Degraded performance · Equipment damage · Safety issue. How the verdicts work.

How to store it

Energizer's band: normal room temperature, 68°F to 78°F (20°C to 25°C), at 35 to 65% relative humidity, and out of prolonged heat, which shortens storage life. Duracell's version adds the packaging — keep cells in the pack they came in, in a dry place at room temperature, until they are needed — and says outright that the refrigerator is neither necessary nor recommended.

Never carry loose cells in a pocket or a bag alongside coins, keys or paperclips.

Sources