Digital Battery 

 BATTERIES

Today’s digital cameras aren't like the venerable Leica that is fully mechanical. They depend on battery power to operate and the camera's LCD monitor and flash can drain your batteries very quickly. If you use the wrong batteries or don’t conserve power you can easily run out of battery power after only a few pictures. In this section we look at the specific issue of digital camera batteries.

 Types of Batteries

The camera you choose normally determines the kinds of batteries you can use. Your choices are quite limited. When adding or replacing batteries for your camera, read the manual that came with the camera to be sure you select the correct type.

 Many cameras us AA batteries, often four of them. If this is the case with your camera, your best choice is NiMH (Nickel-Metal Hydride). Search long and hard, talk to everyone who knows anything, read as much as you can, and the answer is always the same; Nickel-Metal Hydride batteries are what you want. They are rechargeable, environmentally friendly (made from non-toxic materials), and relatively inexpensive. More importantly perhaps, they are designed for high-drain applications such as digital cameras and give you more pictures per charge than any other standard battery type other than the much more expensive lithium ion batteries. If they have any weakness, it's their overall life; lasting only about 400 charge and discharge cycles.

In a pinch you can use alkaline batteries, however don't let their low cost entice you into regular use. Many people buy them for their camera only to discover that they are consumed at a shockingly fast rate. The same is true of rechargeable alkaline batteries. They typically have an even lower capacity than standard alkaline batteries. This means that if a standard alkaline only lasts for a few exposures, a rechargeable alkaline will last for even fewer!

 LiIon (Lithium Ion) batteries are increasingly being used in digital cameras. They last twice as long as NiMH batteries of equal size and don't lose their charge as quickly while in storage. They also have a predictable voltage curve which allows cameras to have a reliable "fuel gauge" indicating how much charge is remaining. They can be charged and discharged as many times as NiMH batteries but normally become unusable after 2-3 years. The problem is that they are not available in as wide a range of models. This means that you won't have much choice when it comes to buying extra batteries or faster battery chargers. 

A related, but non-rechargable battery is the Lithium battery. These batteries come in standard sizes and voltages, deliver two to three times as many shots as alkaline batteries of the same size, and have a shelf life of up to ten years. Their excellent shelf life and high capacity make lithium batteries ideal as spare batteries. The bad news about LiIon batteries is that they are not available in standard sizes such as AA and are much more difficult (expensive) to manufacture. 

Battery ratings

Batteries are rated by voltage and milliamp hours (mAH). Most AA-sized NiMH batteries are rated up to 2100 mAH. A 2100 mAH battery can deliver 2,100 milliamps (mA) for one hour (H). Generally speaking, the higher the rating, the more pictures you can take (all other factors being identical). How many you actually get depends on how energy efficient you are because the camera consumes energy between shots as well as when shooting. If you're careful, you might get about 100 shots per charge. However, if you use alkaline batteries, do lots of zooming and focusing, or leave the monitor on all the time, you might get only 25 or so.

 Choosing a battery charger

There are so many battery chargers on the market it can be hard to choose among them. Just keep in mind that many features add to the cost of a charger. Generally, the faster and more flexible a charger is, the more expensive it will be.

 NiMH and/or NiCad? Most NiMH battery chargers can also handle NiCad cells. But the reverse is not always true. If you want to charge both types of batteries make sure the charger you get is designed for both. Don’t use a NiCad charger to charge NiMH batteries. It won’t necessarily damage them, but it won’t fully charge them either.

Many of the inexpensive NiMH battery chargers are simply NiCad chargers that have been modified slightly. Typically a 5 hour NiCad charger has a switch that allows the charge time to be increased from five hours to eight hours making it into an 8 hour NiMH charger. You might have to be careful when using this type of charger. While it is less expensive to manufacture than a smart charger, it can lead to overcharging and battery damage.

 Size of cells? Most digital cameras use AA size battery cells. However more and more cameras are starting to use proprietary battery sizes. If your camera uses something other than AA or AAA batteries you’ll need to buy a special charger designed specifically for your camera’s battery and your choices will be very limited and probably very expensive. As far as we know, if your camera uses LiIon batteries, you will need to use the batteries and battery charger provided by the manufacturer.

 Number of cells? Since it’s important to keep your batteries together in sets, you will want to choose a charger that can charge the same number of cells that your camera uses. Almost every AA battery charger can charge four cells at once. But if your camera uses only two or three cells, you should get a charger that also charges just two or three cells at a time. Even if your camera uses four cells at a time, you may decide to start using rechargeable batteries in your FRS radio or MP3 player. In that case, the ability to charge two or three cells might be useful.

 Charge time? How quickly a charger charges a set of batteries is probably the most important issue to most people. The speed of a charger also has the biggest impact on the price of the charger. Ignore labels such as "rapid charger" or "overnight charger" and find out how long it really takes a particular charger to charge a set of high capacity NiMH batteries. The fastest chargers on the market (as of 2/2001) can charge 1600 mAh cells in a little over two hours. These chargers have a charge rate of about 800 mA.

It's pretty easy to estimate how long it will take a charger to charge your batteries. Simply divide the capacity of the battery by the charge rate of the charger, then increase the amount of time by about 20% to allow for a certain amount of inefficiency. As an example, a battery with a capacity of 1200 mAh will require about 6 hours to be fully charged by a charger with a charge rate of 250 mA. (1200 mAh/250 mA x120%). Incidentally this example is pretty typical for a standard AA NiMH battery and a typical "rapid charger." Keep in mind that a battery that is only partially discharged will be recharged in less time.

Some people wonder if rapid charging reduces the life of their batteries. It can, but it won't if the batteries and charger are designed for quick charging. With the right smart charger, most NiMH batteries can be recharged in as little as an hour without any damage or reduction in their life.

 Do you mind AC adapters and cords? battery chargers normally get power from an AC outlet. Some chargers plug directly into AC outlets. These plug in chargers have built-in AC to DC converters which provide the DC power necessary to charge the batteries. A plug in charger normally makes for the neatest solution. If you decide to buy a plug in charger, you may also want to look for one with a plug that folds into the charger when it’s not in use.

Many chargers require an external AC adapter known as a "power brick," that plugs into an AC outlet and connects to the charger with a thin power cord. Since the brick and cord adds to the clutter of your home or office, it’s something to consider. In addition to being unsightly, the power brick and cord can be a nuisance when you travel, adding still more clutter to the adapter and cable collection already required by your camera and PC. One advantage of chargers that use a the brick and cord type of adapter is that they often accept a "car cord" that plugs into a car cigarette lighter outlet.

 Charge control. Any battery charger that charges batteries at a reasonable fast rate, needs a way to stop the charge cycle when it’s complete so the batteries are not overcharged. The worst thing you can do to your batteries is overcharge them. The way to prevent this is to use a microprocessor controlled smart charger that monitors the battery charge and knows just the right charge for them. Avoid chargers that charge for a fixed length of time, regardless of what's needed. These 5 or 8 hour "rapid chargers" deliver the same charge to every set of batteries regardless of how much charge they actually need. Their only control is a simple on/off timer. One of these chargers is like a coffee shop waitress who refills everyone's cup at your table with 8 ounces of new coffee, no matter how much is left in each cup. These chargers cause problems two ways:

• If you insert fully charged or partially charged batteries into the charger it has no way to sense this, so it gives the batteries the full charge it was designed to deliver. 

• If you interrupt the charge by pulling the plug and then plugging it back in, a complete charge cycle starts again, even if the previous charge cycle was almost complete.

The best way to avoid these scenarios is to use a smart charger with microprocessor control. The most sophisticated types of actually have separate circuits to monitor the charge level of each individual battery being charged. A smart charger can determine when a battery is fully charged and then depending on its design, either shut off entirely or switch to trickle charge. The point of the trickle charge is to keep the battery fully charged without overcharging it. 

 Dual voltage. If you will be traveling in other countries that don’t have the US standard AC power, a charger that also works with 220 or 240 volts AC is nice to have. Chargers that use an AC brick and cable often have the special AC adapters available as an (expensive) option. Some plug-in chargers automatically work with either voltage.

 LEDs and Audible Alerts. LEDs are standard on most chargers. They make it easy to tell when the charge cycle is complete or if the batteries haven't been inserted correctly. Audible alerts on some chargers are nice, but they certainly aren’t a must have. 

 Car cords. Some chargers that use an AC power brick also have an option to use a car cord. Although these may be useful at times, you'd probably be better off carrying a spare set of batteries in a battery wallet and charging them at night.

 "Trickle" charge. All but the least expensive chargers now provide a trickle or pulse charge mode that maintains the batteries’ charge after the normal charge cycle is complete. Many battery manufacturers do not recommend trickle charging. To be safe, fully charge your batteries and store them in the freezer.

 Conditioning Circuit. Some smart chargers also have a "conditioning" circuit. This is basically just a discharge circuit, which discharges the batteries before it charges them. It can be useful to help prevent the voltage depletion effect that occurs in NiCad batteries, but it’s not too important for NiMH batteries. The only time it’s really useful for NiMH batteries is to quickly condition the cells when they are brand new. Since it takes a few charge/discharge cycles for NiMH batteries to reach their full capacity, a conditioning circuit makes it easy to run the batteries through a few cycles.

 Prolonging your charge

Once your batteries are charged, the goal is to keep them that way as long as possible. When you are out of battery power, you have to stop shooting. There are ways to prolong your battery's charge. In this section we discuss some of them.

 When you first get new rechargeable batteries, charge and discharge them a few times so they get fully charged.

 When photographing, turn off the power hungry LCD monitor and use the optical viewfinder. It's better for taking pictures anyway. When you have to use the LCD monitor, turn down its brightness, or use the black & white mode if it's available on your camera.

 If it's cold out, keep the camera or batteries under your coat to keep them warmer. Cold batteries deliver less power and die faster than warm batteries.

 If the camera is set to full-time autofocus, you'll hear the lens "hunting" for a focus point when you point the camera in different directions. To conserve power, switch full-time autofocus off so the camera only focuses when you press the shutter button halfway down.

 If using NiCad batteries, fully drain and recharge them periodically. The easiest way to do this is with a conditioning charger that drains the batteries before recharging them, or a pulse charger that uses a negative pulse to remove the gas bubbles that build up on the cell plates.

 Occasionally clean the battery contacts in the camera and charger with a cotton swab and rubbing alcohol (isopropyl alcohol). Most charging problems are caused by dirty contacts on the battery or charger.

 When not using the camera for an extended period, remove the batteries and store them in a cool, dry place. (Also remove flash memory cards from the camera when not in use.) 

 NiMH and NiCad batteries start to lose a few percentage points of power a day when stored at room temperature. But they will retain a 90% charge for several months if you keep them in the freezer after they are fully charged. When freezing them, put them in tightly sealed bags so they stay dry and also let them return to room temperature in the same bag before using them.

 When using the camera to display, print, or download images, use an AC adapter so the batteries aren't being drained.

Batteries don't last forever. Depending on their type, they'll last between 400-700 recharge cycles. For heavy users that's about 1 to 2 years. Generally, you can tell they are failing when they no longer hold as long a charge.