Battery Types
Just a few years ago, our battery options were largely limited to disposable alkaline batteries and NiCd rechargeables. Neither type works very well with digital cameras and related gear. Today’s rechargeable NiMHs and Li-ions, as well as lithium disposables, usually are a better choice. Although your choice of battery can be limited by what your device accepts, understanding your battery type can help you get the most out of it.

Rechargeables
NiCd. The old rechargeable standard, these batteries are known for their limited capacity. They also have “memory” effects, which seriously degrade performance and the battery’s life span: Unless the battery is fully discharged before recharging, the battery’s capacity will go down with every recharge cycle until it’s useless. NiCds contain cadmium, a heavy metal that’s decidedly unfriendly to the environment. While NiCds still work nicely for power tools, they’re not your best choice for photo equipment.

NiMH. The first real alternative to alkalines and NiCds, NiMH batteries can store as much as 40 percent more energy than NiCds, and they’re far more resistant to cold than alkalines, providing superior capacity in those conditions. NiMHs don’t suffer from memory problems like NiCds, so you can freely recharge them without needing to drain them all the way first. Since NiMHs can be recharged about 500 times, they cost next to nothing to run.

In flash units, NiMHs recycle your flash in half the time than fresh alkaline batteries. Unlike alkalines, NiMHs’ recycling times won’t get longer and longer as the battery’s charge is used up.

So what’s the catch? Like all rechargeables, NiMH batteries may lose 1 to 2 percent of their charge per day just sitting in your camera bag. If you charge your battery and let it lie around for a few weeks before you use it, you’ll only get a fraction of the shots you were expecting. Let your batteries sit longer between uses, and you could come back to a discharged battery.

Li-ion. These batteries have terrific capacity, they’re much smaller and lighter than other batteries that hold the same energy, and they’re even more resistant to cold than NiMHs. Like NiMHs, they’re free of memory problems, and they can be recharged up to 1,000 times.
Li-ion batteries also self-discharge and will need to be recharged after sitting for several weeks. These batteries require a dedicated charger; if you use a third-party unit, make sure it’s compatible with the battery you’re charging.

Disposables
Alkalines. While alkaline technology isn’t at all new, it works well enough in flash units and other devices that get only occasional use. Alkalines aren’t the best choice if you’re going to be shooting lots and lots of images, but they do have some advantages: Unlike rechargeables, you always can buy more of them at the supermarket—or in the Grand Canyon—and they’re inexpensive.

Digital cameras drain alkalines quickly, making the batteries costly to use if you shoot a lot. In flash units, recycle times increase dramatically as the batteries are used up; before the alkalines are spent, you’ll wait twice as long or more for the “flash-ready” light to come on.

Lithiums. Disposable lithiums greatly outperform most other batteries. Although lithium disposables cost a little over twice the price of an alkaline battery, they last about three to five times longer than the alkalines do in digital cameras and electronic flash units. Like the rechargeables, lithiums recycle your flash unit quickly and maintain most of that speed until they’re used up. They share Li-ion batteries’ resistance to cold and can deliver the bulk of their capacity even in freezing weather.

Lithium disposables also have about double the shelf life of alkalines—if your camera can use them, disposable lithiums make a great backup for rechargeables.

Battery Life
Whichever battery you choose, how you use your camera and the type of pictures you take can affect battery life. One of the best things about digital photography, the LCD monitor, also is among the hungriest for battery power. Turn your camera off when you’re not using it, and keep image review times as short as possible.

For those of us making time exposures at night, keeping the shutter open—and the sensor live—for long periods eats power more rapidly than quick handheld shots. Cooler temperatures at night don’t help power consumption either—if you do a lot of this kind of shooting, make sure to have spare batteries on hand.

“Is It Dead Yet?”
Except for alkaline batteries, which put out less and less power as they’re discharged, other battery types put out a fairly constant voltage until they’re nearly exhausted. That’s generally good news, as it means your gear will keep working consistently while the batteries have juice, but there’s a downside. The first is that apart from the alkalines, there’s little warning of impending battery exhaustion—your batteries can produce normal power levels one minute and be dead shortly thereafter.

Because most battery-check indicators rely on output voltage to estimate batteries’ remaining strength, the indicators in your camera aren’t much better at predicting battery exhaustion than you are. At best, they can merely report that you’re “nearly” exhausted, just before the battery quits.

At their worst, battery-strength indicators can be fooled by unusually heavy drains on the battery—the indicators sometimes can report your battery is nearly dead when it isn’t. These heavy drains can come from repeatedly rapid-firing your camera through a large number of frames and by operation in cold weather. Under these circumstances, the battery indicators can show a depleted charge, but the batteries come back to life some time after the load is removed or after the batteries warm up.

While you also can “rest” batteries that really are nearly exhausted, don’t do it. You risk losing your images—and rendering your media card unreadable—if the battery dies while the camera is trying to write to the card. Using rechargeable batteries that are that close to being completely discharged shortens their life, too. It’s always a good idea to keep a spare battery with you.

Charging Your Batteries
Although Li-ions and NiMHs have eliminated the NiCd’s memory problems, there still are a few things you can do to help the batteries last longer and deliver maximum capacity. The first is to prevent them from becoming deeply discharged—exhausted to the point where internal damage occurs.

Along with ignoring the urge to squeeze out just one more shot from batteries that need recharging, make sure the batteries’ charge levels don’t drop too far while they’re in storage. It’s a good idea to top off your batteries at least once a month, whether you’ve used them or not. Some camera makers offer a dock that keeps your camera battery fully charged automatically—the docks maximize your batteries’ longevity while making sure you’ve al-ways got a camera that’s ready to go.

In the past, the heat generated by overcharging batteries was a threat to battery longevity, but modern chargers use a more advanced, three-stage system to prevent this problem. Avoid using older fast chargers with your NiMHs, or chargers for other kinds of cells. If you’re going out to buy a new recharger, keep in mind that the faster ones generally get your batteries hotter in the process, shortening their life somewhat. Whether the extra convenience makes the batteries’ shorter life span worthwhile is up to you.

Li-ion batteries have dedicated chargers, so you don’t have to worry about overcharging them or how fast a charger to get—just use the charger designed for the battery. Li-ions and NiMHs have one special need, though, and that’s to condition them by fully charging them before the first use, then discharging them all the way before recharging. Repeat this cycle three times, and you’re good to go—you’ll get the best out of the batteries, and you can recharge them whenever you want to.