Why Do Some Batteries Last Longer Than Others?

By Jessica Saras

It's Monday and you're late for work thanks to the sudden death of your alarm clock's batteries--the same ones you replaced not too long ago. Yet while they only lasted a few weeks, the batteries in your remote control have thrived for over a year. So what's the difference between them? Is it the brand? Do more expensive batteries really last longer? And why do some batteries, even when they're the same brand, last longer than others?

When you insert batteries into a device, they have to be positioned in the battery compartment with the positive and negative sides, or terminals, facing a certain way. When properly inserted, the terminals then line up with a wire spring inside the device. This wire acts as a bridge between the two terminals, allowing electrons to flow from the battery into the wire, thereby charging the device and enabling it to function.

Batteries have a very long shelf life, typically lasting a year or more without losing power. Chances are, if a store is selling it, it has not yet expired and will work the same regardless of whether it's purchased a day or a year before its expiration date. So you really shouldn't have to be too concerned with the age of a battery and don't need to look for the pack with the latest expiration date stamped on it. However, even if they aren't ever activated, batteries can lose up to 20 percent of their original power per year if they're kept in a warm area (about 68 to 86 degrees F). Known as the battery's self discharge rate, this loss of power can be reduced if batteries are stored at lower temperatures. On the same token, however, extremely low temperatures can also reduce a battery's charge. So while it may help to store your batteries in a refrigerator, the freezer isn't such a great idea.

Assuming you already store your batteries at an appropriate temperature, what else determines whether or not they last a week, a month or a year? Well, contrary to what those commercials may state, it's really more about the type of the battery rather than the brand. An AAA battery, for example, will last longer than a D battery. In addition, a battery's life is greatly influenced by the product in which it is used and the amount of energy required to make the device work. Although most products like CD players and clocks tend to use less energy, others such as MP3 players and cameras typically require more energy. Lithium, titanium and premium alkaline batteries are designed for these high-energy devices, whereas regular alkaline batteries work best with low-energy devices. In terms of brands, countless studies have been done with independent testing from companies like TechTV and Zbattery.com, but there has been no conclusive proof that any particular brand works better than any other. Rather, the factors that determine how long batteries are based on how they're stored and how they're used.

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