How Long Do Batteries Last?

Every emergency kit has a bag of batteries in it, and almost nobody knows how old they are. The flashlight works when you test it in the kitchen, so the question never comes up until the night it matters. Then you find out whether those cells were bought last spring or during a hurricane scare nobody remembers anymore.

"How long do batteries last" is really three questions wearing one coat. How long a battery keeps its charge sitting in a drawer (shelf life). How long it runs a device once you switch it on (runtime). And, for rechargeables and car batteries, how many years before the battery itself is worn out (service life). The answer depends almost entirely on the chemistry, so that is how this page is organized.

Quick Answer

In storage at room temperature, alkaline AA batteries last about 10 years (Energizer rates its standard E91 AA at 10 years at 21°C), and lithium AA batteries last about 20 to 25 years (Energizer rates its Ultimate Lithium L91 at 25 years at 21°C). Rechargeable NiMH cells can be stored for roughly 3 to 5 years, and modern low-self-discharge types hold their charge far better than the older kind. Lithium-ion packs (phones, power banks, tool batteries) age slowest when stored around 40 percent charge in a cool room. A car battery typically lasts 3 to 5 years in service, closer to three in hot climates, but a car that sits undriven can drain its battery in about four weeks. Heat shortens every one of these numbers.

Key Takeaways

  • Chemistry decides shelf life. Lithium primaries outlast alkalines by more than double in storage, and both beat any rechargeable left sitting.
  • The date on the package is a shelf-life date, not an expiry. An alkaline cell past its date usually still works, just with less capacity.
  • Heat is the enemy of every chemistry. Battery University gives about 15°C (59°F) as the recommended storage temperature for most batteries. A hot car or attic is the worst place to keep a stockpile.
  • Lithium-ion should not be stored full. At 25°C, a pack kept at 40 percent charge retains about 96 percent of its recoverable capacity after a year, against about 80 percent for one kept at 100 percent.
  • Car batteries die from sitting, not just from age. A maintenance charger is the single cheapest piece of vehicle readiness most households skip.
  • For an emergency kit, lithium AAs are the right default. Longest shelf life, widest temperature range, and no leaking alkaline paste inside a flashlight you open twice a year.

Battery Shelf Life by Chemistry

Battery type Typical storage life Best used for Main weakness
Alkaline (AA, AAA, C, D, 9V) About 10 years at room temperature Everyday devices, cheap bulk stock Can leak and corrode contacts; weak in the cold
Lithium primary (AA, AAA) About 20 to 25 years at room temperature Emergency kits, cold weather, high-drain gear Costs more per cell; not rechargeable
NiMH rechargeable Storable 3 to 5 years; needs recharging after storage Devices used weekly Self-discharges; older types lose charge quickly
Lithium-ion (phones, power banks, tool packs) Years of service if stored part-charged and cool Rechargeable electronics, power stations Ages fastest when kept full and hot; fire risk if damaged
Lead acid (car, sealed backup batteries) 3 to 5 years in service; sealed units storable up to about 2 years if kept charged Vehicles, UPS units, small solar setups Permanent damage (sulfation) if left discharged

The alkaline and lithium figures are manufacturer ratings from Energizer's own data sheets. The NiMH and sealed lead acid storage figures come from Battery University's storage guide. Treat all of them as good-conditions numbers: room temperature, dry, and in the original packaging.

Alkaline Batteries: The Default Everyone Owns

Alkaline cells are the cheap, everywhere battery, and they store well. A decade in a cool cupboard is a realistic expectation for a good brand, and the date printed on the package is the manufacturer telling you when capacity is expected to have dropped meaningfully, not when the cell stops working.

Their real problem in an emergency kit is leakage. An alkaline cell left inside a device for years, especially a fully drained one, can leak potassium hydroxide paste that corrodes the contacts and kills the flashlight it was meant to power. Two habits prevent almost all of it:

  • Store spare batteries outside the device, in their packaging or a battery case, and load them when you rotate the kit.
  • Never mix old and new cells in the same device. A tired cell gets driven backward by the fresh ones, which is a common route to leaking.

Alkalines also lose a lot of their output in the cold. Energizer's standard AA is rated to operate from about -18°C to 55°C (0°F to 130°F), and its usable capacity falls well before the bottom of that range. That matters for a winter car kit or a cabin that is not heated when you are away.

Lithium AA and AAA: The Emergency Kit Battery

Lithium primary cells (lithium iron disulfide, sold as "lithium" AAs) are the right choice for anything that will sit for years before it is needed. Energizer's data sheet for its Ultimate Lithium AA gives a shelf life of 25 years at 21°C and an operating range of -40°C to 60°C (-40°F to 140°F). They also weigh less than alkalines and hold voltage better under heavy load, which is why headlamps and GPS units run noticeably longer on them.

The trade-off is cost per cell. The sensible split for most households is lithium in the kits that sit (the go-bag, the car, the weather radio, the smoke-alarm spares) and alkaline or rechargeable in the devices you use every week.

Lithium AAs are 1.5 volt cells designed as drop-in replacements for alkalines. Do not confuse them with 3.7 volt lithium-ion cells of a similar size, which will damage a device built for AAs.

Rechargeable NiMH: Great Value, Poor Hermits

Nickel-metal-hydride AAs are the most economical battery you can own if you use them regularly. Their weakness is sitting. Older NiMH cells lost their charge quickly on a shelf, which is why so many people gave up on rechargeables for emergency gear. Modern "low self-discharge" cells (often sold as pre-charged or ready to use) hold their charge for far longer, and they are the only NiMH worth buying for preparedness.

Battery University gives a storage life of about 3 to 5 years for NiMH and recommends storing nickel-based cells at around 40 percent charge. In practice, for a kit, that means: if you rely on rechargeables, they need to be part of a rotation you actually do, recharged every few months, with a charger and a way to power it. If you will not do that, put lithium primaries in the kit and keep the NiMH cells for daily use.

Lithium-Ion: Phones, Power Banks and Tool Packs

Lithium-ion packs do not have a meaningful "shelf life" in the alkaline sense, because they are always slowly aging whether used or not. What you control is how fast. Battery University's storage data is the clearest picture of it. Estimated recoverable capacity after one year in storage:

Storage temperature Stored at 40% charge Stored at 100% charge
0°C (32°F) 98% 94%
25°C (77°F) 96% 80%
40°C (104°F) 85% 65%
60°C (140°F) 75% 60% after only 3 months

Read that table as a storage instruction. A power bank kept topped up at 100 percent in a warm closet loses a fifth of its capacity in a year doing nothing. The same bank stored at around 40 percent in a cool room loses almost none. For a preparedness power bank, the compromise is to store it part-charged, mark a calendar to check it every few months, and charge it fully when a storm is forecast. A power bank that is 40 percent full when the lights go out is still far better than one that was ruined by being kept at 100 percent in a hot car.

⚠️ SAFETY: A lithium-ion pack that is swollen, punctured, crushed, unusually hot, or has been in floodwater should not be charged or used. NFPA notes that the risk of overheating, fire and explosion rises when these batteries are damaged or improperly used, charged or stored. Store and charge packs away from anything flammable, use the charger made for the device, and dispose of damaged batteries through a battery recycling drop-off, never the household trash. Verify against the manufacturer's guidance for your specific pack.

How Long Does a Car Battery Last?

AAA puts typical car battery life at three to five years. Heat is the main reason for the spread: AAA notes that in hot southern climates a battery typically lasts about three years, while in cooler northern climates five or more is common. Short trips also wear batteries out early, because the alternator never gets the chance to fully recharge them.

How long can a car battery sit without driving?

Less time than most people assume. Nationwide's guidance is that a car battery will typically last about four weeks in a parked car before it risks being too flat to start the engine, varying with the vehicle and the battery's age. Modern cars draw a small current even when switched off, for alarms, clocks and computer memory, and the battery also self-discharges on its own.

For a vehicle that is part of your evacuation plan, that four-week number matters. A second car, a truck you only use for hauling, or a camper that sits all winter is exactly the vehicle that will not start on the day you need it.

How to keep a stored car battery alive

  • Use a maintenance charger. AAA recommends a maintenance charger (a "battery tender") to keep the battery fully charged and extend its service life. It is the cheapest fix on this page.
  • If there is no outlet, disconnect or remove it. Nationwide suggests that for a car sitting more than a month, you remove the battery and store it charged in a dry, ventilated place between 40 and 60°F, giving it a charge about every 12 weeks.
  • Recharge at 70 percent, not at dead. Battery University advises recharging lead acid when it falls to about 70 percent state of charge, which is roughly 12.42 volts on a resting 12 volt battery. A cheap multimeter tells you where you stand. Letting it go flat causes sulfation, which permanently reduces capacity.

How to Store Batteries So They Actually Last

  • Keep them cool and dry. Room temperature or below. Never the glovebox, the attic, or the garage wall that gets afternoon sun.
  • Keep them in packaging or a case. Loose cells rattling together in a drawer can short against each other or against keys and coins. Tape over the terminals of 9V batteries.
  • Store devices empty. Batteries out of flashlights, radios and remotes that sit for months.
  • Date everything. Write the purchase month on the package with a marker. First in, first out.
  • Store rechargeables part-charged and check them. About 40 percent for lithium-ion and NiMH, then top up on a schedule.
  • Standardize your devices. If every light and radio in the kit runs on AA, you need one kind of spare, and you can rob the TV remote in a pinch.

A Simple Battery Plan for an Emergency Kit

  1. Lithium AAs (and AAAs if you must) in the go-bag, car kit, weather radio and headlamps. Replace them on a long cycle, roughly every decade, or when used.
  2. Alkalines or low-self-discharge NiMH for everyday devices, rotated through normal use.
  3. One or two power banks stored part-charged, checked every few months, charged fully when a storm is forecast.
  4. A maintenance charger on any vehicle that sits for weeks at a time.
  5. A way to recharge when the grid is down, whether that is a small panel or a generator. Batteries are storage, not supply.

FAQ

How long do batteries last in storage?

At room temperature, about 10 years for alkaline AAs and about 20 to 25 years for lithium AAs, based on Energizer's ratings for its standard alkaline and Ultimate Lithium cells. Rechargeable NiMH can be stored 3 to 5 years but needs recharging after storage. Heat shortens all of these.

Do batteries expire?

Not suddenly. The date on the package marks when capacity is expected to have dropped to the manufacturer's threshold. An alkaline cell a year or two past its date will usually still run a flashlight, with less runtime. A cell that is leaking or corroded should be discarded regardless of its date.

Do lithium batteries last longer than alkaline?

Yes, on every measure that matters for preparedness. Energizer rates its lithium AA at 25 years of shelf life against 10 for its standard alkaline, and the lithium cell works across a wider temperature range, down to -40°F. It also holds its voltage better in high-drain devices.

How long do batteries last in a car?

A car battery lasts about three to five years in service, according to AAA, with hot climates at the short end. A healthy battery in a parked car typically runs down in about four weeks without driving, so a car that sits needs a maintenance charger or regular drives.

How long does a car battery last without driving?

About a month is a common estimate, and a weak or old battery can fail sooner. Removed from the car, charged and stored in a cool, dry place, a battery can last up to about six months if it is given a charge roughly every 12 weeks.

Should I store batteries in the refrigerator?

It is not necessary for modern alkaline or lithium AAs, which are rated for a decade or more at room temperature, and condensation on cold cells is a risk when you take them out. A cool, dry cupboard is enough. The rule that does matter is to keep them out of heat.

What is the best way to store a power bank long term?

Part-charged, around 40 percent, in a cool room, and checked every few months. Battery University's data shows a lithium-ion pack stored at 40 percent and 25°C keeps about 96 percent of its capacity after a year, against about 80 percent if stored full. Charge it fully when you know you will need it.

Why do batteries leak?

Alkaline cells can vent their electrolyte as they age or when they are fully drained, and mixing old and new cells in one device makes it more likely. Store spares outside the device, remove batteries from anything that will sit for months, and do not mix ages or brands in the same device.

The Bottom Line

Batteries do not keep forever, but they keep a lot longer than the drawer full of mystery cells suggests, if you buy the right chemistry for the job and keep it out of the heat. Lithium AAs for the kits that sit. Alkaline or good rechargeables for daily use. Power banks stored part-charged. A maintenance charger on the car that does not get driven. And a date written on every package, so the night you need them is not the night you find out how old they are. Be prepared. Stay savage.

Related reading: batteries are only storage, so pair this with How Many Solar Panels Do I Need? and How Long Can a Generator Run Continuously? for the recharging side, and What Size Inverter Do I Need? if you are running household loads from a battery bank.

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