What devices are you going to use your 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. 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.
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; 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. Drop-off recycling for disposable batteries, by contrast, is "nearly non-existent." Typically, the only way to recycle this kind of battery is by mail and at your own cost.
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.