Digital Photography For What It's Worth

Batteries for AA-compatible digital cameras—selection, care and feeding for long life and reliable power delivery

On this page—

• Why NiMH AAs?

• NiMH Battery Management 101

• Stretching Digital Camera Battery Capacity

• Temperature And Battery Performance

• AA Battery and Charger Options

• Solar Chargers

• Battery Packs

• Carrying Batteries Safely

• Why Stop with the Camera?

• Reference and Links

Last updated October 22, 2009

Why NiMH AAs?

	If your camera doesn't take AAs, this article will probably be a waste of your time. Click the arrow at left to return to the article index.
	If you're already an NiMH user, click the arrow at left to skip directly to NiMH Battery Management 101.
	If you're already sold on NiMH AAs for routine camera use, the arrow at left will take you directly to the short answer on AAs for digital cameras. Otherwise, read on.

Thankfully, many digital cameras still take 4 (or less commonly, 2) AA batteries of several different types. In decreasing order of utility, these include

• nickel-metal hydride (NiMH, rechargeable)
• lithium (non-rechargeable)
• nickel-cadmium (NiCd, rechargeable)
• alkaline (non-rechargeable)

Surprised to see alkaline AAs dead last? Practically speaking, they hardly belong on the list, as explained below. And what about lithium ion batteries? Their electrochemistry isn't compatible with the AA format.

Why Favor AAs?

My steadfast preference for AA-compatible cameras rests on these undeniable AA charms: 

• Highly standardized.

• Cheap—at least compared to most proprietary alternatives.

• Compatible with a wide array of readily available chargers, which are also cheap thanks to competition in a large market.  

• Available in a pinch wherever civilization is found.

Granted, proprietary lithium solutions deliver longer runtimes, but NiMH AAs offer a combination of availability and bang for the buck that's hard to beat. 

AA Variants

As batteries go, AAs are highly standardized, but some AAs have more insulation around their negative terminals than others.

Inadequate insulation around AA negative terminals can result in shorts in some cameras.

Shorts involving low-resistance rechargeables like NiMH AAs can cause serious camera damage. If your camera is AA-compatible, the manual will probably spell out which makes or negative terminal configurations are compatible with its battery compartment. Don't let this dissuade you from using rechargeable AAs, but do confirm compatibility before buying.

CR-V3 Disposable Lithiums

Newer AA-compatible cameras like the Oly C-30x0Z, C-4040Z and C-2100UZ have added non-rechargeable lithium polymer CR-V3 batteries to their usable battery lists. A pair of CR-V3s replaces 4 AAs. Each CR-V3 has the size, general shape, voltage and connections of a pair of AAs joined side-by-side, but CR-V3s work only in AA-compatible cameras specifically designed for them. Older AA-compatible cameras like the Oly C-2020Z can't handle them, as Oly warns here.

Kodak claims that one of their CR-V3s delivers up to twice the runtime of a pair of disposable lithium AAs. At twice the price of the lithium AAs, you've lost nothing on the cost/capacity front, and you've gained the convenience of 50% fewer battery changes with the CR-V3s. 

Compatibility and availability are the only real CR-V3 downsides that I can see. Old-fashioned AAs can be used in any AA-compatible device that happens to need them. As of 4Q2001, CR-V3s were turning up in chain drug stores and discount retail outlets like Office Depot, but I still wouldn't count on finding them on the shelves in an emergency. You'll still have much better luck with disposable lithium AAs in that regard. 

Proprietary Camera Batteries

Unfortunately, higher-end cameras requiring proprietary rechargeable lithium-ion or lithium-polymer batteries are becoming more and more commonplace. For legitimate safety reasons among others, these batteries always require proprietary chargers.

Rechargeable lithium batteries have many, many virtues (too bad suitability for the AA format isn't among them), but the real beneficiaries of this trend may not be the photographers. I'm fully aware of the safety and voltage issues (there's no getting around the 3.6V chemistry) driving nonstandard formats in lithium rechargeables and chargers, but I'm no fan of proprietary batteries in digital cameras—however competent they may be—and will not cover them further here.

The Best of Both Worlds

The Olympus E-10 and E-20 digital SLRs combine the best of AA and lithium worlds with a very clever and flexible design I'd like to see spread to other cameras. The versatile E-10/20 battery bay accepts

• a pair of CR-V3 lithium disposables

• 4 rechargeable NiMH or disposable lithium AAs in a special holder

• the contact arm of a proprietary high-capacity lithium polymer battery pack that attaches to the E-10/20 baseplate.

Nice going, Oly! Now if only those E-10/20 lithium battery packs were actually affordable.

Bundled Doesn't Mean Recommended 

With AA-compatible cameras, it's important to distinguish between the battery you find in the box with your new camera and the one you'll actually use on a routine basis. Many first-time digital camera buyers take the manufacturer's shipping choice as some sort of directive, but the alignment of interests here is limited at best.

Choosing a battery for routine use is up to the user. Making the right choice is one of the main thrusts of this article. 

Bundled AA-compatible batteries are increasingly lithium non-rechargeables and decreasingly alkalines—the lithiums probably for their long shelf life and good performance, and the alkalines for their very low cost. Bundled NiMH AAs and chargers are pretty scarce now, but that's OK: We're all better off purchasing them separately to keep down camera prices, to avoid duplication for the now many who already own them, and to insure getting the right gear for the long haul ahead.

If your camera came with lithium non-rechargeables, resist the urge to shoot them up and instead carry them as emergency and cold-weather back-ups—a role for which they're ideally suited. (No one working for a living can afford to use lithium disposables routinely.) If your camera came with NiMH AAs, you're off to a good start, but be sure to take a cold, hard look at the supplied charger before assuming that you're all set.

If you found alkalines in the box, don't even bother loading them in your camera.

But wait, how could that be? Why would alkalines be bundled with new digital cameras if they're so badly suited to task? Everyone knows that alkaline AAs are universally available, reliable and cheap. Or so they seem. 

Geez, Why Not Alkalines?

This is one of the first questions new digital camera users ask, usually right after discovering the hard way how poorly alkalines perform in their camera.

The answer boils down to voltage and current delivery, the latter an inescapable issue far from the minds of most battery users. Unlike the most familiar portable electronic devices, digital cameras draw currents ranging from a trickle of tens of milliamps while asleep to a walloping amp or more during memory card writes. Keeping up with a digital camera at its hungriest takes a high-drain battery—one willing to dish up charge very rapidly on demand without a big drop in voltage. Alkaline batteries simply aren't up to this task.

Granted, alkalines store a lot of charge — typically upwards of 2500 mAh per AA. But when they meet a high current load, voltage droop quickly renders them impotent long before their charge can be fully tapped, at least from the standpoint of a camera requiring a certain minimum voltage to operate. Several factors contribute to alkaline voltage droop, including

• an inherently high internal resistance

• electrolyte depletion in the reaction zone with slow recovery due to an unsophisticated but cheap to produce internal cell geometry that hampers remixing

• electrolyte dilution in the reaction zone due to the electrochemical production of water with slow recovery once again due to that cheap diffusion-limiting cell geometry

A typical digital camera running on alkalines shuts down within a dozen shots for lack of adequate instantaneous voltage and current flow, not available charge. Simply put, the alkalines choke up, and the bigger the draw, the bigger the voltage droop and current shortfall. An early battery withdrawal ensues, and everyone ends up mightily frustrated. To alkaline users familiar only with low-drain devices like flashlights, radios, CD and tape players, games, calculators and remote controls, this dismal high-drain performance often comes as a rude surprise.

Should such behavior be grounds for an early alkaline/digicam divorce? Absolutely, and the sooner the better! In most digital cameras, you'll find alkaline batteries of all types impractically short-lived and most unkind to both your wallet and the environment.

Just say no to alkalines.

Yes, that includes alkaline rechargeables and overly expensive new-fangled "high-current" alkaline formulations like the Duracell Ultras and the Energizer Titaniums, too.

If Not Alkalines, What?

Nickel-metal hydride (NiMH), of course. For routine use, none of the commonly compatible AA alternatives can match the winning NiMH combination of 

• Standard form factor (AA)

• Low cost—under $2.50 per AA

• High capacity (1300-1850 mAh per AA and climbing)

• Excellent high-drain performance—just what digital cameras demand

• Flat discharge curve—you can actually draw most of the rated capacity

• Light weight

• Carefree rechargeability—charge them whenever you like without fear of a NiCd-like "memory effect"

• Minimal maintenance—very occasional conditioning will bring you peak performance, but it's by no means necessary

• Long service life (500-1,000 charges per AA)

• Environmentally friendly, thanks to their reusability and lack of toxic heavy metals 

I'd say that's pretty close to a recipe for the ideal digital camera battery. Team up NiMH chemistry and efficient internal cell design with the flexibility and economy of the AA format and you've got yourself a hard-to-beat power delivery system for digital photography.

OK, What's the Catch?

Are there downsides to NiMH AAs? After 2 years of heavy NiMH use and lots of reading, I can think of only two minor practical issues with a very simple workaround:

• A moderate but entirely workable self-discharge rate

• Limited but rapidly improving off-the-shelf availability

The workaround for both? Carry one or more spare sets. It's cheap and easy.

NiMH Self-Discharge

All rechargeable batteries lose charge spontaneously (self-discharge) over time. NiMH batteries do so faster than lithium rechargeables, to be sure, but NiMH self-discharge has been perfectly tractable in my experience. I commonly get satisfactory runtimes from my NiMH AA sets 3-5 weeks out from their last top-off. Carrying extra sets completely eliminates any residual power shortage concerns. Frankly, I find the NiMH self-discharge issue way overblown on public forums like RPD,

Freshly charged NiMH batteries are commonly said to lose 10% of their capacity in the first 24 hours and 1-2% daily thereafter at room temperature. (High ambient temperatures speed self-discharge while cool temperatures slow it.) At a conservative 1.5% per day after the 1st day, that leaves a residual charge of 58% at the end of the first month. If you're coming down from, say, 1600 mAh, the remaining 928 mAh per AA will still power quite a few shots. And to put that into perspective, recall that 1200 mAh rechargeable AAs were considered "high-capacity" not so long ago.

My own experience with several different NiMH AA brands suggests a much slower self-discharge rate—more on the order of 75% residual capacity after a month on the shelf. 

At $8-10 per set, extra battery sets are the cheapest and best defense against self-discharge—and a great convenience on many other fronts to boot.

I don't consider it worth the hassle, but if you find yourself laying awake at night worrying about NiMH self-discharge, or in an unusually hot environment, you can refrigerate your charged NiMH AAs to slow their self-discharge. Just be sure to seal them in a plastic bag to fend off condensation and to warm them to room temperature before use to reap the full benefit of your efforts.

NiMH Availability

You're still not likely to find NiMH AAs or chargers at the local supermarket or hardware, but Radio Shack is always a good bet locally, and chain retailers like K-Mart, Wal-Mart, Target and Best Buy have recently entered the NiMH market in a big way, typically with Rayovac offerings. Camera shops offering digital gear are also likely sources, but their prices are often gougy. There are also many NiMH sources online. For selection, quality, pricing and service, Thomas Distributing has long been the online NiMH vendor to beat. 

Some of these NiMH sources are discussed briefly below.

AA Bottom Line

Cost and environmental considerations aside, nothing beats lithium performance—particularly when it comes to shelf life and cold weather current delivery. Cost considered, NiMH rechargeables pop up again as the clear choice for all-around routine digital photography use. In fact, as you'll see below, NiMH rechargeables are a great option for just about any solid-state electronic device taking AAs—as long as you're willing to abide by a few simple NiMH care guidelines.

	If you're now sold on NiMH AAs, you can skip directly to the short answer; otherwise, look over the technical data supporting the NiMH recommendation in the AA comparison table below.
	If you're already an NiMH user, you might want to skip directly to NiMH Battery Management 101.

Digital Camera AA Comparison

The table below summarizes the important differences and similarities among AAs commonly compatible with digital cameras.

Table note: Compiled from several sources but primarily from Eveready's battery application manuals and the Cadex website. Prices accurate as of 4Q2001.

* Since alkalines deliver digital camera runtimes hundreds of times shorter than the other battery types in the table above, multiply the cost for 1,000 uses by 100 to get feel for just how wasteful alkalines really are in digital cameras.  

Still Need Convincing?

Some final mud-slinging for those still resisting the call to NiMH...

NiCd AAs

Environmentally, the cadmium in NiCds is a disaster, but high-capacity (1100 mAh) NiCd AAs are otherwise reasonable 2nd choice for digital cameras—provided they're charged properly and conditioned frequently in a sufficiently smart charger of recent vintage. (Forget about resurrecting that clueless NiCd charger you mothballed in the garage in 1994—chances are, it'll overcharge and ruin your new NiCds just like it did the old ones.) 

Because of the highly toxic cadmium they contain, NiCds should always be recycled, never discarded. Contact an Ace Hardware near you for recycling details. Hats off to Ace for providing this valuable community service.

Lithium AAs and CR-V3s

If you can't go the rechargeable route, please consider disposable lithium AAs or CR-V3s instead of alkalines. Disposable lithiums will 

• Deliver many, many times the runtime of alkalines in digital cameras at a surprisingly favorable cost ratio (relative to alkalines, that is). 

• Recharge your onboard flash in a flash.

• Retain their punch in a shelved camera for 7-10 years.

• Deliver their current in freezing weather.

• Be as kind to the environment as a disposable battery can be. 

At $8-10 per 4-pack, lightweight, long-lasting disposable lithium AAs may seem overpriced compared to alkalines going for $5-8 per 4-pack, but they last hundreds of times longer than alkalines in digital cameras and 3-4 times longer in low-drain applications like radios, CD players and flashlights.  You do the math. 

IMO, lithiums are the battery of choice for devices capable of draining their batteries below the 1.0V safe minimum for rechargeable NiMH batteries. Flashlights and other non-solid state devices fall into this category.

Unfortunately, high-drain rechargeable lithium AAs will probably never see consumer use for a number of electrochemical and safety reasons. 

Alkaline AAs

If for some bizarre reason you decide to stick with alkalines after all that's been said (and you'd be amazed at how many folks on RPD seem determined to do just that), get the so-called "high-drain" variety. (Look for "high current" or something to that effect on the packaging.) They'll perform a tad less miserably than than regular alkalines in digital cameras.

And for heaven's sake, resist the urge to toss your "spent" disposable alkalines when your camera goes dead. They've still got lots of capacity left! If you let them cool for 20-30 minutes, you may be able to nurse a few more shots out of them. After that, redeploy them in any low-drain device—a TV remote, CD player or clock, for example—and you'll recoup some of your monetary investment. 

Of course, you'll still have to write off the shots and composure you lost while replacing batteries umpteen times per 32MB memory card, but hey, it was just your kid crossing the plate after her first home run.

Rechargeable alkalines participate fully in the high-drain voltage droop that plagues alkaline chemistry, but at least they take a little longer to reach the landfill.

Just say no to alkalines.

At Last, the Short Answer on Digital Camera Batteries

From the earliest days of consumer digital cameras, rechargeable nickel-metal hydride (NiMH) AA batteries have been the portable power source of choice, and they're likely to remain so well into the future.

• Get 2-4 sets of NiMH AAs for routine use. (Consider high-capacity NiCd AAs only if you can't get NiMH AAs.)

• Don't even think about using alkalines on a regular basis. 

• Carry at least one set of non-rechargeable lithium AAs or CR-V3s as emergency/cold-weather back-ups. (They're also an excellent choice for cameras that see only light and very sporadic use.)

• Take care of your NiMH batteries, and they'll take care of you. Get a smart, fast conditioning charger to keep it simple.

• Consider a battery pack for extraordinary power needs.

NiMH Battery Management 101

Good quality NiMH AAs will deliver years of cost-effective service—conservatively 500-1,000 charges per battery—provided they're properly used and maintained. Using the right charger makes it easy to do the right thing.

Practically speaking, NiMH AA performance involves 2 separate issues for digital camera users:

• Runtime—how long the batteries last on the job in the camera. 

• Overall service life—how many charge/discharge cycles they'll endure before runtimes drop irreversibly to unacceptable levels.

Luckily, what's good for one is generally good for the other. Your battery management strategy can address both at once.

First, Do No Harm

That one-liner from the Hippocratic oath is the perfect starting point for NiMH battery management. To avoid shortening runtimes and service life, everyone agrees that you must

• Charge, deploy and condition loose rechargeable NiMH AAs in fixed sets, as if they were part of a battery pack.

• Avoid overcharging like the plague it is.

• Do whatever you can to avoid overheating during charging. 

A smart charger that knows when to quit on its own is the key to success here. Deploy your charger in a cool, well ventilated area. If your charger has a cover, leave it open during charging if possible.

Conditioning

If you do nothing more than follow the guidelines just given, your NiMH AAs will live long and prosper. But getting the very most bang from your batteries will require just a bit more effort:

• To maximize runtimes, condition your batteries—once when first entering service and then very occasionally when runtimes begin to sag noticeably. Typically, that will occur near the end of the set's service life, which can be stretched a bit with judicious conditioning. 

• Between conditionings, favor shallow discharges over deeper ones to maximize service life—but don't make a religion of it.

With a fast conditioning charger to speed you through largely unattended conditioning cycles, the pain/gain ratio should stay well within tolerance. That said, bear in mind that repeated deep discharges can shorten service life considerably and unnecessarily.

Too much NiMH conditioning is far worse than none at all.

I freely admit that the utility of NiMH conditioning remains controversial in forums like RPD, but I've experienced the benefits of conditioning first-hand. For the $8-10 a replacement set of NiMH AAs will cost you, these efforts may not be worthwhile for you, but they have been for me. 

Look Ma, No Memory!

Don't worry about recharging your NiMH AAs before they die in your camera. If you avoid overcharging your batteries, you'll never see the voltage depression or so-called "memory effect" we all came to know and hate in NiCds back in the early 90's.

At under $2.50 per NiMH AA, I'd be more than willing to give up quite a few theoretical cycles out of 500-1000 for the considerable convenience of charging whenever I please—as opposed to when the batteries reach a certain depth of discharge. But my reading of the Cadex battery website suggests that shallower discharges actually beget more cycles, so 

Charge your NiMH AAs whenever it's convenient.

BTW, to keep service life in perspective, consider this: With a total of 4 NiMH AA sets and a fair amount of shooting, it took me 2 years to use up maybe 150 cycles in my oldest sets.

It's All in the Charger

The battery management strategy I'm propounding here may sound like a lot of trouble to the uninitiated, but it's actually a piece of cake with the right charger—one that's fast and smart and does the conditioning for you.

There'll be more on chargers below. For now, here's the short answer: Get the very smart, plenty fast Maha MH-C204F conditioning charger, its smarter and faster MH-C401FS update (sans conditioner), or something very much like it. This relatively inexpensive, deservedly popular charger will pretty much do it all for you:

• It will fully charge 4 AAs from camera-dead in 2-3 hours.

• It won't overcharge, period.

• It will condition your AAs at the touch of a button when you decide they need it.

• Its 12VDC input can be powered with either an included AC adapter or an optional but frequently bundled car adapter worth its weight in gold.

• Its small, light and easy to pack.

With a charger like that, you're out of excuses.

For further details on the basic battery management guidelines already given, read on; otherwise skip directly to the Stretching Digital Camera Battery Capacity.

Always Use Rechargeable Batteries in Sets

Why bother keeping sets of batteries together? Here's why:

Warning: Batch-charging batteries in different states of discharge can easily damage the batteries, the charger or both.

To facilitate battery use in sets, it's a good idea to

• Dedicate 2-4 complete sets of NiMH AAs to your digital camera.

• Mark the sets clearly—e.g., with an indelible pen on thin transparent tape as shown below—so they can be rotated through the camera and charger easily without risk of shuffling them.

Keep your sets together. If you need to replace AAs in a set, stick with the same make and capacity and try to get the new and the old AAs in sync separately as best you can before charging and using them together. A simple battery meter like the $9 Radio Shack 22-096C simplifies the matching of NiMH AAs.

Extra Battery Sets

At $8-10 per set, extra battery sets deliver tremendous value on many practical fronts, day in and day out. You'll certainly have a hard time getting more bang for the buck with any other digital camera purchase. 

For starters, carrying 4 extra NiMH AA sets allows you to

• Stop worrying about the state of the batteries already in your camera. Just shoot them up and change batteries when the time comes.

• Shoot away with the LCD blazing without worrying about scrimping on power in the field. (Try as I might, I have yet to exhaust 3 sets of 1450+ mAh NiMH AAs in one day of heavy shooting with heavy LCD use.)

• Leave one or more sets behind in the charger (at home, in the car or in your hotel room) while you click away in the field.

• Get past NiMH self-discharge anxiety—no more worrying about when your sets were last topped off.

• Power camera-based TV viewing and cable image transfer sessions without an AC adapter while other sets are recharging.

• Rotate warm batteries into the camera as needed in freezing conditions.

The importance of the battery set concept and the value of extra battery sets and a smart fast charger with a car adapter cannot be overstated.

If you choose to invest in extra sets, space-saving battery caddies will become a practical issue.

Honey, I Cooked The Batteries!

NiMH AAs are very robust as rechargeables go, but overcharging is a sure way to ruin both runtimes and service life. Overcharging begets overheating, which cooks the battery chemistry in untoward and sometimes irreversible ways. Conditioning can sometimes reverse the symptoms of overcharging, but it's not a safe bet. Prevention remains the only surefire cure.

Repeated overcharging is very much a cumulative poison for NiMH AAs. One result is the so-called "memory effect" often attributed to NiCds and occasionally to abused NiMH batteries as well. But the "memory" the afflicted battery appears to develop turns out to be nothing more than a reduction in runtime due to the thermal and ultimately chemical ravages of overcharging. NiMH batteries never subjected to overcharging will develop such behavior only in their dying days. 

Technical Note: There may a true NiMH/NiCd memory effect, but it's strictly a laboratory phenomenon and remains controversial even in that realm. You'll never see it in routine use.

Chargers, Smart and Otherwise

If overcharging is the problem, chargers and their users are a big part of the solution. When it comes to overcharge prevention, some chargers are a lot "smarter" than others. The same applies to users, but we won't get into that.

The smartest chargers, like the venerable Maha C204F, the newer Maha C401FS and the faster Rayovac PS4, monitor and respond to several different overcharge indicators. When overcharging seems immanent, they throttle back to a safe trickle current that NiMH batteries can tolerate indefinitely. Since fast chargers are more prone to overcharge and overheat batteries than slower ones, they'd best be pretty smart, but the really cheap fast chargers are often anything but.

The dumbest chargers rely on the user to know when to pull the plug. For a slow overnight charger that starts out at a trickle (well under C/10) and stays there, it's fairly safe to be dumb, but buying a dumb fast charger is just asking for trouble. The reality is that few of us can be trusted to babysit battery chargers, myself included.

Many commercially available chargers fall somewhere in between smart and dumb, slow and fast. Trusting them to protect your batteries based on their specifications can be an iffy proposition. User-to-user recommendations gleaned from forums like RPD can be helpful here.

You'll find more on NiMH charger selection below. For now, consider these 2 equally reasonable strategies:

1. At under $30 delivered, the very smart, fast Maha MH-C204F conditioning charger is both a great convenience and a sound investment in long-term battery protection. Its slightly more expensive MH-C401FS update and the similarly priced Rayovac PS4 are equally good choices.

2. Alternatively, spend $8-10 on a dumb overnight charger and put the money saved toward an extra battery set or two. Even with the 1-2% average daily NiMH self-discharge rate, having extra charged spares around will nicely offset the slower charger throughput. You won't have a way to condition, but your NiMH AAs will do well.

Remember, cheap fast chargers are usually too dumb to be safe. If you're not on top of them, they'll cost you in batteries.

Hot's Not Cool

It's perfectly normal for NiMH AAs to become fairly warm during charging, but if any of them become uncomfortably hot to the touch, remove them from the charger immediately, no matter how smart the charger. Many sources quote 130°F (54°C) as the maximum safe charging temperature. To the touch, that's a little hotter than average hot tap water.

When charging NiMH AAs get overly hot, assume something's wrong: Your sets have gotten mixed up, a battery in the set has gone bad, or perhaps the charger's not so smart after all. If your charger or batteries routinely get hot during charging, I'd look for another charger. If you notice melting of any battery parts, including the plastic jackets, discard the affected batteries immediately; an internal short is likely.

Warning: Never, ever install overheated batteries in your camera while they're still hot!

Overheated batteries may well survive the cooking—this time—but wait till they've cooled to load them. At least one RPD poster claims to have seriously damaged an Oly C-2000Z in just this way.

Keeping cool

You can help your charging AAs keep their cool by charging them in a cool, well-ventilated place. Creating an air gap underneath your counter-top charger also helps. If your charger has a cover that can be left open during charging, do so if safety considerations (e.g., small children) permit. 

Overnight and Maintenance Charging

For long-term charging, make sure your charger's trickle current rating in milliamps (mA) is no more than 5-10% of the rated capacity (C, in mAh) of the batteries to be charged.

For example, it's safe to leave C = 1500 mAh AAs on trickle charge for days at a time in a charger rated at C/10 = 150 mA or less.

Indefinite or maintenance charging for weeks or months at a time should probably occur at currents well below C/10, but how far below remains controversial. I've seen credible sources quote "safe" maintenance currents of C/10, C/20, C/40 and even C/300 in this context.  The 5% (C/20) recommendation is probably safe in this context.

Check your charger's trickle current rating before applying it indefinitely. At the 24 mA (under C/50) trickle rate of my Maha MH-C204F charger, I'm willing to bet that few of my AAs' 500-1000 lifetime cycles are at stake.

Condition Your Batteries—Show Them You Care

To make your NiMH batteries the best they can be, you'll need to perform initial and very occasional maintenance conditionings. With the right charger, it's a snap. While many continue to question or flatly deny the utility of conditioning NiMH batteries in general, my NiMH batteries have responded favorably to these simple measures:

• Run new NiMH batteries through 3-5 initial conditioning cycles—full charge, then moderate discharge (to ~1.0V)—before putting them into routine service to insure maximum capacity and service life.

• After initial conditioning, recondition your NiMH cells very occasionally to revive them when performance—primarily runtime per charge—clearly begins to sag. Expect to perform maintenance conditioning only near the end of service life, which can be stretched a bit with judicious conditioning. Maintenance conditioning may also improve runtime drops due to chronic overcharging, but the important action line there is to stop overcharging. 

Properly done, I see no real downside to this program, but keep in mind that...

You can't properly condition NiMH batteries using your camera alone.

There's no way around it—solid-state electronic devices like digital cameras shut down and stop drawing current long before their batteries reach a depth of discharge effective for conditioning. That said, there's nothing wrong with shooting up the charge in the AAs you're conditioning, provided you finish them off as a set in some other device capable of completing a proper discharge after the camera dies.

It's also worth repeating here that

Too much conditioning is far worse than none at all.

Repeated deep discharges can shorten service life considerably and unnecessarily.

Conditioning Chargers

The safest and easiest way to condition is with an NiMH-specific conditioning charger with a built-in discharging circuit that safely limits the rate and depth of discharge and can be activated whenever needed. An excellent example of such a charger is the smart, fast, compact, inexpensive and  deservedly popular Maha MH-C204F conditioning charger, which conditions at the touch of a button. Far and away the best of several good NiMH chargers I own, I heartily recommend the C204F to any NiMH AA user.

Forget the Flashlight

Although I seem to have gotten away with it in my foolish youth, I no longer recommend discharging NiMH AAs in a flashlight (or any other analog device) because...

Discharging NiMH AAs below ~1.0V can lead to irreversible loss of performance due to polarity reversal or anode oxidation.

The benefits of NiMH conditioning are not worth the risk of battery damage. If you lack the wherewithal to limit the discharge phase properly, it's better to forego conditioning.

Depth of Discharge

Between conditionings, NiMH battery manufacturers claim that shallow discharge/charge cycles are more conducive to long NiMH service life than deep ones. I have no reason to doubt them here.

It's probably not worthwhile to adhere to a rigid charging regimen in this regard—after all, NiMH batteries would remain your best bet economically even if they died fairly young. But you might as well swap out and top off whenever it's convenient to do so.

And don't worry—there's no real memory effect with NiMH batteries. (Truth be told, there probably wasn't one with NiCds, either, but that's another story.)

Stretching Digital Camera Battery Capacity

The strategy is simple: When power is in short supply, avoid the camera functions that consume the most, store and use your batteries at the proper temperatures, and take advantage of external power sources whenever you can.

• Avoid using the LCD monitor, whatever it takes. The LCD's the single biggest power sink in your camera.*

• Avoid running the zoom lens motor. Turning a zoom camera on and off forces the zoom lens to extend and retract with each power cycle. If your zoom camera has a sleep mode, leaving it on between shots may well be a better power conservation strategy. (This is certainly the case for the Oly Camedias.)

• Avoid using the onboard flash.

• Use your camera and batteries near room temperature as best you can.

• Store charged spare batteries in the coolest place you can find at or above freezing, but be sure to bring cold batteries back up to room temperature before using them.

• Use an external card reader whenever possible.

• Use an AC adapter to power studio, surveillance or TV review sessions and any unavoidable serial cable transfers.

* Watch out for camera modes that automatically turn on the LCD and leave it on. Aperture-priority, shutter-priority, manual exposure, sequence, manual focus, macro and panorama modes are examples on the Oly C-2020Z. Once in the first 4 modes, you can kill the LCD manually and still work unhindered, but manual focus, macro and panorama work requires TTL control via the LCD. 

Temperature and Battery Performance

Several experience-based RPD reports have warned of poor digicam performance under freezing conditions, probably due to cold batteries.

Cold Saps Usable NiMH Capacity

In a week of winter shooting in the Colorado Rockies at freezing temperatures down to 10°F (-12°C), I never encountered a problem I could link to the cold. My NiMH-powered Oly C-2020Z sat fully exposed on a tripod for over an hour one frigid morning without complaint. A 3-hour hike in a blowing snowfall at 20°F (-6°C) produced many pictures, all without a hitch. 

To what extent reported cold weather problems reflect known NiMH battery limitations vs. other cold-related camera malfunctions is hard to sort out. LCDs are known to slow down in the cold, but I've never noticed it. According to their manuals, my Oly C-2020Z and Oly D-340L are designed to operate in the 32-104°F (0-40°C) range, but the C-2020Z has performed flawlessly down to 10°F (-12°C). Since several RPD posts have also reported good camera (as opposed to battery) performance at temperatures well below freezing, I suspect that cold batteries underlie most cold-weather digital camera malfunctions.

Whatever the camera contributions, cold NiMH batteries clearly have a hard time. As the tables below show, NiMH rechargeables lose at least 20% of their deliverable capacity at freezing (32°F, 0°C) without significant loss of voltage; at -20°C, they've lost 80%. Fortunately, the trapped capacity becomes available again on return to room temperature.

Since cold NiMH batteries behave like batteries of lesser capacity, be prepared for reduced runtimes in freezing conditions. Carrying extra sets of batteries in a warm pocket is a must with NiMH in the cold. When the cold batteries in the camera fail, rotate in a warm set. Once the cold set has warmed up, its residual capacity will be ready to tap.

Battery Packs

Another way to beat the cold is to use an external battery pack warmed by body heat in a pocket, say, or beneath your coat. It's also a good idea to keep the camera warmed this way to whatever extent possible, particularly to avoid internal condensation on returning indoors.

Cold NiMH batteries suffer mainly from reduced  discharge capacity. Source

Lithium AAs To the Rescue

Non-rechargeable lithium AAs like CR-V3s and the Energizer L91s shown below fare much better in the cold than their NiMH counterparts—hence their deserved reputation as the cold-weather battery of choice. Add a 7-10 year shelf life and excellent run-time and high-drain performance, and you'll see why lithium non-rechargeables make ideal backup batteries for digital photography.

Discharge curves for Eveready L91 non-rechargeable lithium AAs at 20°C and -20°C illustrate their advantage in the cold. Source

Note that rechargeable lithium AAs are not likely to appear anytime soon for a number of legitimate safety and electrochemical reasons.

Heat Accelerates NiMH Self-Discharge

Cold isn't the only problem. At room temperatures (68°F, 20°C) NiMH cells self-discharge by about 1-2% per day, as the graph at right clearly shows. Crank that up to 99°F (37°C)—e.g., in a car parked at a sunny trailhead—and you'll loose additional total carried capacity by more than doubling the self-discharge rate. Source

How lithium batteries fare in the heat, I don't know.

Cold Storage for NiMH Batteries

Luckily, the opposite effect also obtains: Refrigerating stored NiMH batteries will preserve capacity by slowing self-discharge. The Energizer NiMH reference manual, for instance, recommends storing NiMH batteries at the lowest possible temperature in the 0-30° C range.

Remember, however, that cold is no friend at discharge time, as noted above. Cold NiMH batteries may deliver capacities well below their rating, but once warmed, available capacity will recover completely.

When returning NiMH batteries to service from cold storage, bring them back up to room temperature or thereabouts before using them.

Be sure to refrigerate charged NiMH batteries in clearly marked, sealed plastic bags to keep your battery sets together, to protect them from shorts, condensation and spills, and to discourage pilfering by other refrigerator users. Big scary radiation stickers come in handy here.  

AA Battery And Charger Options

Options abound nowadays when it comes to NiMH batteries and chargers. I'm convinced that battery management has a lot more to do with NiMH runtimes in the field than battery brand, at least among the better marks. Those who manage to avoid overcharging and overconditioning will be rewarded with good NiMH runtimes, and the key ingredient there is a reliable smart charger. IMO, performance differences among NiMH AA brands aren't worth worrying about. Nor would I let 100-200 mAh gains in rated capacity tempt me away from investing in extra battery sets. Chances are, you won't notice that extra bit of capacity in the field, but you will notice the security and convenience extra sets bring.

NiMH AAs

Rated capacity C (measured in milliamp-hours, or mAh for short) is only part of the NiMH AA performance story. Runtime is what really counts in the field, and total deliverable watt-hours is generally a better predictor of runtime, but C is usually all you'll have to go on. To make matters worse, manufacturers seem to apply some very idiosyncratic rounding rules when rating their own capacities. Batteries rated at 1800 mAh test out all over the map—mostly on the low side of 1800. Finally, the electrochemical tweaks that bring higher capacities also tend to increase self-discharge rate. Take your pick.

When shopping for NiMH AAs, pay careful attention to 

• rated capacity 

• cost per Ah 

For digital cameras, stick with 1500+ mAh AAs and think twice about paying the premium for the highest capacity AAs currently on the market.

NiMH AA Brands

NiMH AAs are not all created equally, but brand-related runtime differences are as hard to pin down as they are unimportant. Powerex (Maha), Rayovac, Nexcell (Maha), Olympus, Kodak and Sanyo (GE) brands generally get good press on RPD. The negative battery sagas posted there are hard to interpret without knowing how the problem batteries have been managed or used. I've had good luck with Nexcells and very good luck with Oly-brand and Sanyo AAs, but so much for anecdotes. For a well-executed comparison test of the NiMH AAs available as of 3Q2002 (and a good discussion of some of the technical issues involved), see Dave Etchells' excellent article The Great Battery Shootout!

Whatever brand you favor, keep in mind that

Rated NiMH battery capacity isn't always a reliable predictor of battery runtime in the field.

For example, testing conducted by Arthur Bleich for a 1999 Digital Camera Magazine article found that Quest Gold 1500 mAh AAs lasted only marginally longer than Quest standard 1300 mAh AAs. The latter cost much less.

Look at Cost Per Capacity

The highest capacity NiMH AAs on the market always go for a premium, and in my experience, that premium is seldom worth paying—except perhaps for those with 2-AA cameras like the Oly D-40. 

Check the math for 1600 Maha Powerex vs. 1800 mAh Nexcell AAs at December, 2001 prices:

In my experience, extra battery sets are much better insurance against power shortage than fewer sets of slightly fatter batteries. Extra sets also largely eliminate practical concerns like charger throughput, NiMH self-discharge and unknown state of the batteries already in your camera. By all credible accounts and from my own observations, the  difference between 1600 and 1800 mAh is not all that noticeable in the field. Of course, higher capacity AAs can save you a little weight and volume if you need to carry 8 or more sets on a long trip, but is that worth a 33% premium in cost per unit capacity? Not for me.

NiMH Chargers

Branded NiMH batteries and chargers sold by camera manufacturers are generally no better than 3rd party chargers and AAs and usually cost much more if purchased apart from the camera. Kodak chargers and batteries seem to be an exception. I recommend going with the Maha MH-401FS or MH-C204F or the Kodak charger discussed below and spending some of the savings on one or more extra battery sets.

Whatever you do, get a charger with a 12V car adapter. 

A 12V car adapter will give you essentially unlimited power capacity on car trips, in-car charging the world over and last-minute top-offs at the trailhead.

Fast Chargers

When shopping for a fast charger for your NiMH AAs, know how your candidates prevent overcharging. Of the several strategies available—voltage monitoring, temperature monitoring and timing, among others—none are foolproof, so the "smartest" chargers rely on more than one. As with birth control, timing is by far the least reliable method.

Shop around for NiMH chargers, but be sure to consider these 3 outstanding options: 

• The ever-popular Maha MH-C204F charger bundle from Thomas Distributing (a steal at $31 as of 4Q2002) includes a very smart, fast (500 mA) NiMH/NiCd AAA/AA charger, a set of 4 Maha Powerex 1700 mAh AAs, a 110-120V AC adapter and a 12V car adapter. The C204F also features a built-in conditioning circuit activated at the touch of a button. The 24 mA trickle charge rate is safe for indefinite charging. (For the bundled C = 1700 mAh AAs, that's ~C/70.) Several different AC adapters for international use go for $12 each. You'll find the C204F favorably reviewed here.

• The newer, faster 4-circuit 100-minute Maha MH-C401FS charger from Thomas Distributing ($48 as of 4Q2002) includes a very smart, very fast (1000 mA) NiMH/NiCd AAA/AA charger, a set of 4 Maha Powerex 1800 mAh AAs, a 110-120V AC adapter and a 12V car adapter. The C401FS lacks the built-in conditioning circuit of the C204F but offers instead a "gentle" 5-hour (300 mA) charging mode to preserve service life when you're not in a hurry. With 4 independent charging circuits, it's ideal for devices (like FRS radios) taking an odd number of AAs. Its 50 mA trickle charge rate is safe for indefinite charging. (For the bundled C = 1800 mAh AA, that's C/36.) As with the C204F, international AC adapters for international use go for $12 each. You'll find the C401FS favorably reviewed here.

• The solid Rayovac PS4 1-hour NiMH/NiCd charger gets excellent press on RPD and is widely available at competitive prices in national retail outlets like Target, K-Mart, Wal-Mart, Best Buy and Walgreens among others. This smart, fast charger lacks a conditioning cycle but monitors and charges each of its 4 AA/AAA bays individually. The PS4 typically comes bundled with 4 of Rayovac's 1600 mAh NiMH AAs. As of 4Q2001, Warren Melnick and many other RPD denizens have reported months of Rayovac NiMH AA use with no complaints. A separately sold "Car Kit" includes a 12V car adapter—an indispensable item in my book. Sorry, I don't have information on pricing or adaptability to non-US power sockets at this time. 

• The Kodak PhotoLife Charger Kit, also available from Thomas Distributing ($39 as of 4Q2000), includes a compact, lightweight, smart, fast (650 mA) compact charger and a set of 4 Kodak 1450 mAh NiMH AAs. The 110-120V fold-down wall-socket prongs on this one-piece unit make it a great choice for travel to civilized portions of the US. This unit is nearly identical to my discontinued but still heavily-used Oly B-20CU charger. I'm glad Kodak picked up the design.

• The Olympus B-40SU charger and battery kit available from buy.com ($40 as of 4Q2000) includes a smart, fast (490 mA) Olympus B-100E multi-voltage NiMH AA charger and a set of 4 Oly-brand NiMH AAs. The charger operates at 100-240V at 50-60Hz. The capacity of the AAs appears to be a secret. The charm here is the ability to use foreign wall sockets using only the inexpensive socket adapters you're probably already carrying.

These are all smart microprocessor-controlled units with temperature sensing.

Another consideration for international travelers is the smart, fast Ansmann Powerline 4 NiMH AA/AAA conditioning charger, a 4-bay 100-240V 50-60 Hz 700 mA wall unit that monitors, charges and reports each bay separately. There is no 12V car adapter available, but the Ansmann comes with interchangeable plugs for 4 different international socket configurations. The design of the 2-prong US plug allowed the unit I tested to sag a bit under its own (relatively heavy) weight, but it managed to stay in the socket nevertheless. Now sold in US camera shops, the Ansmann goes for nearly double the online cost of the Maha MH-C204F—more than you'll pay for a C204F bundle plus 2 different international AC adapters. 

Maha's bulkier, less convenient, more expensive but more versatile MH-C777 universal NiMH/NiCd charger from Thomas Distributing is another good smart, fast conditioning charger. It's not as well suited to travel as the chargers just mentioned, but an optional 12V cigarette lighter adapter can be had.

Overnight Chargers

Cheap fast chargers are seldom smart enough to use without careful supervision, but it's usually safe to leave your AAs in inexpensive trickle or overnight chargers for extended periods. Just make sure the trickle charger's current rating in milliamps (mA) is no more than 10% of the rated capacity (C, in mAh) of the batteries you intend to charge. For example, it's safe to leave C = 1500 mAh AAs charging indefinitely in a trickle charger rated at C/10 = 150 mA or less. Because NiMH AAs safely tolerate long-term charging currents in mA up to C/10, chargers this slow generally don't need to be smart. Most overnighters fall into this category.

Cheap and slow may be safe, but slow charging promotes crystallization within NiMH cells and reduces overall service life.

Smart, fast chargers are well worth the extra cost over time.

Maintenance Charging

Indefinite or maintenance charging for weeks or months at a time should probably occur at currents well below C/10, as discussed above. Check your charger's trickle current rating before applying it indefinitely. The Maha MH-C204F charger has a safe trickle rate of ~C/60.

Notable Battery and Charger Suppliers

Thomas Distributing

For affordable, high-quality NiMH AAs in bulk, NiMH battery packs and a wide selection of NiMH AA chargers—including solar chargers for back-country use and several smart fast conditioning chargers with 12V car adapters—it's still hard to beat Thomas Distributing. I've been happy with all my Thomas purchases, but several other on-line NiMH battery sources also have their RPD supporters. I hear that resellers operating on eBay can beat Thomas' prices; whether the hassle and risk are worth the savings is another matter.

Buy.com

It's always worthwhile to see if buy.com has what you want. Their delivered prices are generally good to great, and their selection, service and return policies are hard to beat. 

Radio Shack

Radio Shack offers several good counter-top NiMH-compatible chargers, including some fairly sophisticated units with proponents on RPD, but I have no further information on these. Their very compact overnight (14 hour) NiMH-NiCd charger with a fold-down plug in back looks like a dandy travel/camera bag charger at $8 last I checked. 

Radio Shack entered the NiMH battery scene with above-market prices and below-market capacities several years ago and remain there as of 4Q2001. Their October, 2001 retail price of $19.95 for a 1200 mAh NiMH AA 4-pack is no bargain, but if you're willing to sacrifice money and capacity for off-the-shelf availability, you may find some solace in the decent performance ratings their NiMH AAs get on RPD. 

Target

Target generally has great prices on disposable lithium AAs. They sold the Energizer e2 lithium 4-pack at right for $10 in July, 2000.

Better yet, the reclosable e² plastic bubble pack makes an ideal battery caddy.  The 10-year expiration date is typical of lithium disposables. Target also carries the smart, fast Rayovac PS4 1-hour NiMH/NiCd charger and 1600 mAh Rayovac NiMH AAs.

In fact, other large discount retail, electronics, drugstore and office supply chains have all become good bets for lithium AAs as of 4Q2001. Few online vendors seem to have tumbled to the sales potential here, but many of the ones that have still seriously overcharge for lithium AAs.  Shop carefully—lithium AAs seem to invite gouging. As of February, 2000, any price below $3.50 per AA is decent. $2.50 per lithium AA is still a true battery value as of 4Q2001. 

Solar Chargers

The basic solar charger from Thomas Distributing shown below charges four 1350-1500 mAh NiMH AAs in about 9 hours in full sunlight. How smart is the charging circuitry? Not very, I suspect, but this slow charger probably doesn't need to be smart. As noted above, NiMH AAs can withstand indefinite trickle charging below 0.1C without harm, so battery safety isn't likely to be an issue here, but I haven't been able find or measure the maximum current rating of this unit.

The IGP solar NiMH AA charger catching some rays. The far bay in the photo at right stores a second set of 4 AAs. On the trail, I envision the charger riding in a mesh bag clipped to the top of my backpack. In camp, I see it basking with the lizards on a rock.

Thomas Distributing now sells a more elaborate solar charger that can also power electronic devices directly.

Battery Packs

Let me say at the outset that I have no personal experience with battery packs. NiMH AAs have served me well thus far, but then I seldom find myself in the pack-favoring situations most often cited by those on RPD who prefer battery packs over loose AAs:

• Long, busy shoots

• Studio sessions involving a lot of moving around with the camera

• Travel with limited charging opportunities

• Freezing weather

The last item deserves a little explanation. Battery performance generally suffers in the cold, particularly with NiMH chemistry. Keeping an external battery pack warm with body heat while the camera does its thing out in the cold allows you to preserve your precious battery capacity, even in frigid conditions that would bring NiMH AAs operating inside the camera to their knees.

Battery packs may save you battery changes, but they come with hassles of their own. For one thing, there's a power cord to deploy and store. (Cords and I don't get along.) Some find operating a camera tethered to a belt pack a nuisance; others don't seem to mind. Some packs are much heavier or bulkier than others. Your needs should point the way to your best compromise.

For studio or surveillance work from a fixed camera position near an AC power source, an AC adapter may be a better choice than a battery pack.

Battery Pack Runtimes—Still a Puzzle

Battery packs vary widely in useable capacity—some with little if any more runtime than a good set of NiMH AAs. I have yet to figure out how to estimate potential battery pack runtimes based on rated capacities and voltages.

Based on end-user reports on RPD, some battery packs with rated capacities near those of commonly available NiMH AAs appear to last a good bit longer than the AAs while others with even higher ratings fall short. The higher voltages packs tend to deliver (6.0-7.2V vs. 4.8V for a set of 4 NiMH AAs in series) are no doubt part of the equation, but to what extent? Inaccurate ratings and other factors are likely to figure in as well.

If anyone out there really understands the runtime vs. capacity issue for battery packs, I'm eager to be educated.

Manufactured Packs

As of 4Q2000, MAHA now offers two compact POWERBank® battery packs—a 6.0V, 1800 mAh NiMH version for $55 and a 7.2V, 1400 mAh lithium-ion version for $65. (The NiMH version got a favorable review here.) Both come with an LED-based charge indicator, a belt-clipped holster and a not-so-smart 4-hour charger with AC and cigarette lighter adapters. Best of all, both come with a single output cable and a set of 3 modular plugs, one of which is likely to work with your digital camera. (Watch that polarity!) RPD users have found the the charge indicator to be of limited reliability. The higher-voltage, lower-capacity lithium-ion pack suffers less from self-discharge between uses, but in my experience, the NiMH self-discharge issue is much overblown. Whether your camera can safely handle the 7.2V lithium-ion output may be difficult to ascertain prior to purchase.

Other commercial NiMH belt packs like the Unity Digital 2700 mAh ProPower and the DigiPower Solutions 2700 mAh DPS-8000 require proprietary camera-specific connector cables. As of 1Q2000, the ProPower went for ~$100, cable included, while the DPS-8000 cost ~$60 after buying the separately-sold cable. Both packs come in fitted leather cases with belt clips.

In informal testing conducted by Ricky Lo of BugEye Digital and reported on RPD in 4Q1999, the compact DigiPower DPS-4000 1200 mAh NiMH pack gave 291 consecutive identical flash shots compared to 209 from a set of 1200 mAh rechargeable AAs. That modest 39% gain in staying power is 61% less than you'd get simply by carrying a 2nd set of AAs.

The unique SR Electronics' PowerGrip line offers NiMH packs in 3750 and 1875 mAh capacities built into the handle of an aluminum camera bracket. These non-removable packs include a slave flash sensor and sync circuit with a PC cord giving your external flash slave sync capability. SR is considering a detachable pack able to operate off-bracket in cold weather or when carrying a bracket isn't feasible.

Homemade Packs

Gadgetmeister Al Jacobs has kindly posted his simple, detailed, well-illustrated plans for an economical heavy-duty build-it-yourself rechargeable 6V 4000 mAh pack made from a commonly-available sealed lead-acid (SLA) battery and some Radio Shack cabling.

With the 4000 mAh battery, Al's homemade pack weighs about 2 pounds, and with the smaller 2800 mAh version of this battery, about 1.5 pounds. By comparison, the compact 2700 mAh NiMH ProPower pack weighs around half a pound. (The substantial weight difference reflects differences in both chemistry and battery size.) 

Besides their weight disadvantage, lead-acid batteries don't take kindly to being run flat and left there. Be sure to keep lead-acid batteries at least partially charged to prevent irreversible sulfation.

According to Al, if there's a cold-weather performance hit with his lead-acid pack, it must be small because he has yet to see it. This observation jives with everyone's experience with lead-acid car batteries: The chemistry performs well in the cold, at least when well-charged.

Many RPD posts have sung the praises of Al's pack, which is particularly well-suited to busy shoots supported from a car. However, if size and weight are more important to you than cost and capacity—say, in a backpacking setting—an NiMH pack like the ProPower may be a better fit.

For a frank discussion of the heartbreak of battery droop and yet another take on battery packs, this time favoring NiCd batteries, see Dan Rutter's "End your digital camera battery problems" page.

For an inexpensive 4,500 mAh NiCD battery pack made from an old fanny pack, "Hi-Capacity" NiCd D cells and some off-the-shelf parts from Radio Shack, search for "Ken Spencer" on Andy Baird's superb battery page. Andy describes several additional homemade battery pack options.

Carrying Batteries Safely

Why talk about battery safety with 1.2V AAs? The short answer (pun intended) is current:

Warning: Shorted NiMH AAs can deliver currents as high as 7 amps!

That's the kind of juice jumper cables are made to handle. 

At best, inadvertent battery shorts waste precious capacity. At worst, they can lead to camera bag and pocket fires. (I hate it when that happens!) Luckily, it's physically impossible to short 4 AAs amongst themselves when stored alone in an insulating container—even a loose-fitting one. The concern is what's outside the container, and how easily it might come into contact with the battery terminals.

The Ideal Battery Caddy

My ideal battery caddy would be a safe, light-weight, tight-fitting, completely enclosed, unbreakable container that

• contains exactly 4 AAs to help me avoid mixing up battery sets,

• takes up minimal space—a commodity always in short supply in my camera bag,

• loads, unloads and packs away easily—preferably with one hand,

• closes securely, and

• resists penetration by metal objects that could short the batteries.

Four AAs abreast (||||) or in a square bundle (::) would seem to be the most useful form factors, but 2 pairs end-to-end (==) also works well in my small and medium-sized bags.

Charger As Caddy

Until recently I carried my spare NiMH AAs in a compact Oly B-20CU travel charger. It was a great solution while I had room for it:

• The batteries were well protected from their neighbors in the bag.

• The loaded charger was only modestly larger and heavier than the batteries themselves.

• The charger was easy to load and unload, even with one hand tied up with the camera.

• The charger and dead batteries were ready to stick in a wall socket when I got home.

• The refreshed batteries and charger were then ready to drop right back in the camera bag for the next shoot.

• Long-term storage in the charger never noticeably accelerated the baseline NiMH self-discharge rate (1-2% per day).

What could be simpler? If additional gear hadn't overcrowded my bag, I'd still be carrying that charger.

Now I carry the gutted Radio Shack AA holder illustrated below, but makeshift and commercially available battery caddies continue to pop up. Below are some the better solutions I've run across on RPD and elsewhere.

Commercial Offerings

The best ready-made battery caddy I've found to date is a soft nylon 4-AA battery wallet sold exclusively at greenbatteries.com, a worthwhile site promoting the use of rechargeable batteries in all electronic devices (see also below).

These tough, reasonably-priced velcro-flapped wallets meet all my criteria for the ideal caddy. In fact, they make nifty little nanobags for memory cards and filters as well. CompactFlash card and microdrive users will probably prefer the roomier Hakuba pouch, however.

If you carry these wallets on your belt with any frequency, keep an eye on their belt loops. After a couple months of heavy belt duty, the stitching holding the lower end of the belt loop came undone—thanks in part to my not-so-svelte waistline. Luckily, I caught the tear before the wallet fell off my belt. To my mind, attaching the loop to the bottom of the wallet with velcro would have been a more robust solution—one that would also have accommodated wider belts and allowed the wallets to come on and off without undoing the belt.

Hakuba Battery and Memory Card Pouch

On-line camera supply houses sell the 4-AA zippered black nylon Hakuba battery and memory card pouch (now a reasonable $4.00 from www.photosolve.com as of 4Q2001). The Hakuba lacks its own belt loop but comes with a metal clip that could easily attach to a trousers belt loop instead. As a SmartMedia memory card user, I personally prefer the smaller battery wallet already discussed (I have both), but CompactFlash and microdrive users may well find the roomier Hakuba caddy a better fit. Quite a few RPD posters have endorsed the Hakuba. 

Case Logic DMC1 Digital Media Case

Case Logic makes a 6 x 3.5 x1" zippered vinyl and nylon pouch that holds 4 AAs, several memory cards and filter or two. It's too large to fit in most pockets and lacks a belt loop or clip, but the DMC1 has its RPD supporters.  

Some Assembly Required

Plastic AA battery holders like those sold at Radio Shack and Thomas Distributing are close to ideal as battery caddies—once you've removed the metal snap leads (like those on a 9V battery) and all the internal wiring. The surgery's easy enough with a drill, a wire cutter and a pair of needle-nose pliers.

	Failure to remove the metal fittings from these AA holders greatly increases the risk of a damaging short—especially if all the contained AAs are carelessly loaded in series between the well-exposed and easily-shorted snap leads.

I now routinely carry a gutted Radio Shack 8-battery AA holder like the one shown at right. The head-to-head loading precludes a series connection. For added safety, a tightly fitting velcro band (here undone) held in place with a foam mounting strip covers the positive battery terminals in the holder's midsection. Spent batteries go back in heads out. The AAs snap in and out easily in the field, even with one hand. With a battery set at each end, it's also a snap to keep the sets from getting mixed. Set labels are easy to check.

As safe as this arrangement has proven in the field, I still feel a need to keep small loose metal objects out of the same camera bag compartment.

Other Commercial Offerings

A recently-spotted thin neoprene "battery sock" holding 2 AAs seems an overpriced step in the right direction at $6.

Recycled Caddies

Recycled containers are preferable to bought solutions on at least 2 fronts—cost and environmental soundness. 

My current favorite recycled caddy is the near-ideal recloseable clear plastic bubble used to package the Energizer e² lithium battery 4-packs shown above. 

James Farmer and others have recommended the credit card-sized clear vinyl pockets  used to package the lens cleaning cloths sold for $5-6 at upscale sunglass shops. Some of these apparently have a velcro closure. I've occasionally used a similar pocket that came with the microfiber cleaning cloth bundled with my last set of prescription lenses. It's not rigid, but it meets most criteria for an ideal caddy.

Don Wiss recommends the clear plastic container used for Bayer Aspirin 4-packs he found at his local drugstore's checkout counter. It holds 4 AAs. As Don put it, "A bit expensive for aspirin, but cheap for a case."

The most tempting RPD suggestion? Plastic Cadbury Yowie candy containers are purportedly a perfect fit for 4 AAs, at least for those in the UK. (They may not be sold in the US.) Chocolate and a good battery caddy, too—it doesn't get any better than that. 

Ziplock bags have had plenty of advocates on RPD, but IMO, most plastic bags are too puncture-prone to be trusted.

More than one RPD post has recommended backup tape cases, but I haven't been able to find any that fit. My 4 mm DAT tape cases won't quite close with AAs inside, but they're otherwise very close to an ideal caddy. My old QIC80 cases are too large (they hold 6 AAs very loosely).

One RPD visitor recommended an ordinary audio cassette case as an 8-AA holder, but none of the ones I've found so far meet my criteria. I came across some cheap, rather flimsy unbreakable translucent soft plastic cases capable of holding 8 AAs rather loosely, but they're neither rigid nor secure enough for my taste, and the invitation to mix battery sets in an unpartitioned 8-cell container leaves me cold. The much more common hard clear cassette cases are far too brittle, but that's moot: AAs won't fit in the tray in the base of the lid anyway.

Why Stop With The Camera?

If you're willing to abide by the simple NiMH management guidelines above, you'll find that you can use NiMH AAs to advantage in almost any solid-state electronic device running on AAs. Over time, you'll enjoy

• Better battery performance

• Lower operating costs

• The warm and fuzzy feeling that comes with reduced environmental impact.

What kind of devices can you profitably power with NiMH AAs? Nearly any AA-compatible device with solid state electronics that'll shut down before discharging the NiMH AAs below ~1.0V per cell, including

• Portable radios and CD, tape and MP3 players

• Two-way radios like the Motorola Talkabouts

• Handheld and palm PCs, and even some notebook and laptop PCs

• Voice recorders

• Solid-state toys like the Nintendo GameBoy and the Lego RCX computer

(Hint: Many of the proprietary rechargeable battery packs sold for these devices—often at exorbitant prices—are nothing more than NiCd or NiMH AAs soldered together, sheathed in plastic and imprinted with a fancy-looking logo.)

For flashlights and other non-solid state devices capable of draining their batteries below the 1.0V safe minimum for NiMH AAs, I strongly recommend disposable lithium AAs instead. They cost twice as much as alkalines but last 3-4 times longer. That adds up to substantial savings over time.

For more information on extending the use of rechargeable batteries in an increasingly disposable world, please visit Stephen Dougherty's admirable and informative greenbatteries.com site.

Been There, Done That?

Tried the rechargeable battery bit with NiCds and hated it years ago, you say? Well, try it again with NiMH batteries and a smart, fast NiMH charger—I promise you'll like it.

And what's different now, you ask with understandable skepticism, thinking back to all the  video camera NiCds you've cursed in years past? Everything important, that's what!

Remember, NiMH batteries aren't suitable for all devices running on AAs:

Don't use NiMH AAs in flashlights or other (mostly analog) devices that can run them down below ~ 1.0V.

As noted above, overdischarging can cause potentially irreversible damage to NiMH batteries. 

Not Yet Convinced?

To get yourself off the dime, think about all the other things you could be doing with the money now supporting that never-ending one-way transfer of wealth from you to the disposable battery folks. 

Then close your eyes and visualize hordes upon hordes of sad little dead disposables marching off zombie-like to your local landfill. According to the EPA Battery Management website, the more than 2 billion used batteries thrown away in United States each year account for "88% of the mercury and 54% of the cadmium deposited into our landfills."

Need I say more?

For more information on NiMH and lithium AAs, see Thomas Distributing's NiMH FAQ page, the references below, and the battery links on the dpFWIW home page.

References and Links

(See also the home page links.)

Andy Baird's Battery Page—a superb source on all digital camera battery options. If you read nothing else....

Batteries—Dennis Curtin's Short Course on digital camera batteries.

Cadex battery website—Gobs of in-depth material on all battery types in lay terms, including discussions of application and engineering considerations I've not seen elsewhere.

greenbatteries.com—Stephen Dougherty's admirable site is "devoted to advancing the use of rechargeable batteries," which happens to be a favorite cause of mine as well. The Battery FAQ, Battery Myth and Charger FAQ articles are well worth a visit.

Maha MH-C204F charger FAQ—solid NiMH and charger information straight from the manufacturer.

MH-C777 Universal Charger Conditioner Instruction Manual, Maha Communications, Inc.

NiMH application manual—more than you wanted to know, from a major battery manufacturer.

NiMH battery FAQ—what you need to know, from Thomas Distributing, a respected on-line battery and charger vendor.

Unless explicitly attributed to another contributor, all content on this site © Jeremy McCreary

Comments and corrections to Jeremy McCreary at dpFWIW@cliffshade.com, but please see here first.

URL: http://www.cliffshade.com/dpfwiw/batteries.htm