What the best batteries have

  • Long shelf life. Every battery gradually loses its charge over time. Alkaline batteries last 5 to 10 years in storage, while lithium batteries last 10 to 15 years. Rechargeable batteries lose power faster than disposable ones, but newer low self-discharge (LSD) batteries -- the kind that often come pre-charged and ready to use -- hold their juice better than others. An old-school rechargeable battery holds about 50 percent of its charge after a year of storage, while an LSD battery can retain as much as 85 percent.
  • For rechargeables, short charging time. How long it takes to recharge your batteries depends partly on what charger you use. Even in the same charger, however, some batteries recharge faster than others. Professional tests are the best source of information on charging times.
  • Long life. For a disposable battery, battery life is simply how long it can power your device. For a rechargeable, there are two factors to consider: how long it can run on a single charge and its service life, or how many charging cycles it can survive. Some newer rechargeables, such as the Panasonic Eneloop, allegedly last for over 2,000 charge cycles.

Know before you go

What devices do you need batteries for? Just about any battery can power a low-drain device like a remote control or a flashlight. However, for high-drain devices like cameras, battery life varies widely, depending on type. Lithium batteries generally last the longest in high-drain devices, but rechargeable ones can provide better long-term value, especially in devices that see a lot of use. If you're choosing rechargeable batteries for a high-drain device, look for a high capacity, as measured in milliampere-hours (mAh). The higher the mAh rating, the longer it will run on a single charge. However, high-capacity batteries also cost more and don't have as long a service life, so they're not worth using for low-drain devices.

How will you store your batteries? Heat and humidity can shorten a battery's shelf life. However, according to experts, it's a myth that batteries should be refrigerated to prolong their life. This was true for old carbon-zinc batteries, but for today's alkaline batteries, any reasonably cool and dry place will do. Some experts recommend against keeping loose batteries in a pocket or purse where they can clash against other metal objects, such as paper clips or coins. This could short-circuit the batteries, resulting in overheating or leakage.

Do you plan to recycle the batteries when they die? If so, rechargeable batteries are your best choice. There are more than 30,000 locations in the U.S. and Canada that will take rechargeable batteries for recycling, including large chain stores such as Sears, Target, Walmart and Home Depot. (You can find a site near you at Call2Recycle.org.) Drop-off recycling for disposable batteries, by contrast, is hard to find in most areas. The exception is Vermont, which has over 100 drop-off locations in retail stores, libraries, and other public areas. Other states have a few drop-off locations, but often you have to recycle this kind of battery by mail at your own cost.

Value expectations: The dollars and cents of it

If you're investing $10 or more in a set of rechargeable batteries, you'll want them to last as long as possible. Experts recommend using a "smart" charger to prolong battery life. Smart chargers, which are available for as little as $10, can sense when a battery is fully charged and shut themselves off automatically. Less expensive chargers, by contrast, simply run for a fixed length of time. Batteries may end up undercharged, giving you less than full power, or overcharged, shortening their life. Any charger that is a smart charger will say so on the label. Testers at TheWirecutter.com particularly like the Panasonic Advanced Charger BQ-CC17 (Est. $17), which comes bundled with four AA Eneloop Rechargeable batteries.

Basic battery safety

When alkaline batteries get old, they can develop leaks. The fluid inside them, potassium hydroxide, is harmful to eyes and skin. As it dries, it reacts with carbon dioxide to form potassium carbonate, a white powder that's much more stable, but can still damage your devices. Here are some tips to prevent leaks and deal with them if they occur:

  • If you're not planning to use a device for a few months, remove the batteries before storing it.
  • Before putting in new batteries, wipe down the compartment and the battery contacts with a rough cloth or a clean pencil eraser. Always check to make sure you're putting the batteries in the right way around.
  • Don't mix batteries. If a device needs more than one battery, choose batteries of the same type (alkaline, lithium, or rechargeable) and similar age.
  • If a battery feels hot, smells odd, changes its shape or color, or looks strange in any other way, don't use it.
  • Never attempt to recharge a disposable battery. It could explode.
  • Don't get batteries wet, expose them to fire or heat, pierce them, or hit them with anything heavy.
  • If fluid from a leaking battery touches your skin or eye, rinse with plenty of water and seek medical attention.
  • If a battery leaks inside your device, you can neutralize the white powder with a cotton swab dipped in acid, such as lemon juice or white vinegar. Dab it gently on the powder and let it fizz. Then gently wipe away the residue with a cloth or toothbrush.
  • Dispose of used batteries promptly, and keep them out of reach of children.