If your kids play with lots of battery-operated planes, trains, and other such toys (and inevitably leave them powered on), loading up on packs of generic batteries at the dollar store may seem like a swell idea. The problem, as Wired showed through a series of experiments, is that the batteries are packed with less energy than name brands. They may be adequate for something like a flashlight that is used infrequently; for heavy use, it's dollar-wise over the long haul to save the hassle of constantly replacing power cells by spending more upfront on higher-quality batteries. Moreover, cheap batteries are known to leak, which can damage electronics.
Another way to tell if dollar-store batteries are a good buy: Check the label. If the batteries contain carbon zinc, be sure to pass. This component is inferior to the lithium used by name brands.