MORE POWER for your digital camera!

The second worst thing about digital cameras, after their price, is their battery consumption. Even models without power-sucking LCD screens and flashes still eat batteries faster than film cameras, because of the amp-hungry onboard electronics. Many digital cameras run from AA cells (a "battery" is more than one cell), usually four of them, and they’re renowned for draining a set of alkaline cells in less than an hour of shooting. Sometimes much less.
My own Kodak DC120 can certainly do this trick. Its current draw varies from 200mA (milliamps; 1000 milliamps are one amp) when it’s turned on but not doing anything to about 1.2A when its LCD screen is in full power-vampire mode. It can peak at about 2A right after taking a picture.
If you look at the specifications for AA cells, though, you’ll find that an ordinary AA alkaline is meant to have a capacity of 2.4Ah (amp hours). This means it should be able to deliver 1.2A for two hours before going flat. But it falls far short of this performance. Why?

Lies, damned lies, and cell capacities

Cell capacities are commonly quoted based on a "C/20" load – a load that flattens the cell in 20 hours. A 2.4Ah AA cell can be asked to deliver more than ten times C/20 by a camera. In this situation, its voltage drops precipitously and its life is greatly reduced; the most demanding cameras draw so much current that they can’t run from alkalines at all!
D size alkalines have a capacity of around 15Ah. This makes them rather good value, when you consider that they cost only about 50% more than AAs. The C/20 load for a 15Ah cell is 750mA, so they’re only facing about twice their rated load from the average digital camera battery. D cells will therefore deliver rather more of their rated capacity into such a load than AAs. But you still won’t get the duration you’d expect.
Newer kinds of alkalines like Energizer’s "Advanced Formula" and Duracell’s "Ultra" cells perform a bit better under high-load conditions, but not a lot. Lithium AA cells cost three times as much as alkalines and can in medium-draw applications like film cameras give three times the life – although two times is a better bet – but, again, they don’t much like the super-high loads from digital cameras and will give you poor value for money. "Rechargeable alkaline" cells are worse yet. Don’t even think about using cheap dry cells.
Rechargeable cells have capacities much lower than those for alkaline non rechargeable ("primary") cells. About 1Ah is a common rating for good nickel-cadmium (NiCd) and nickel metal hydride (NiMH) rechargeables. Cheap NiCds often have a capacity of only 600mAh; NiMH AA cells are available with capacities up to 1.3Ah. These cells also have a lower output voltage – only 1.2 volts against the 1.5 from non-rechargeables.
But they handle high output currents much better than the primary cells, because their internal resistance is more than ten times smaller. Under a 1A load, 1.5 volt alkaline cells of all sizes commonly droop to only 1.1 volts. But a 1.2 volt NiCd’s output voltage will barely droop at all, and it’ll deliver its full rated capacity without breaking a sweat.
(A cell that can’t deliver high enough current to run a camera any more will probably have a fair bit of capacity left for less demanding applications. So if you’re using alkalines in your digital camera, don’t throw them away when the camera says they’re flat – try them in a lower current device, like a pocket radio or a remote control. You may be surprised how long they last.)
For this reason, and because they’re much cheaper in the long run, rechargeable cells are very popular among digital camera users. Two or three sets of rechargeables should last for an afternoon of photography, if you go easy on the LCD and flash usage. On the down side, ordinary NiCd chargers take at least a few hours to pump these cells back up again. "Trickle" chargers take about 14 hours.
(NiCd and NiMH cells have excellent shelf life, but they won't hold a charge for long, just sitting there. It varies with the CASIO NP-20 Battery, but generally half of a NiCd’s charge will leak away in a month, and NiMH cells are even worse. So if you leave your camera sitting around with rechargeables in it, bear in mind that surprisingly little charge may be left when you suddenly need to use it.)
The solution to the long charge times problem is a better charger. For this, forget the electronics store, and go to a hobby shop. You can get a charger intended for model car battery packs for around $100, and many such chargers are eminently capable of charging a digital camera’s cells – all you need to do is buy a 4xAA cell holder for less than $2 and put a connector on it that the charger can plug into or clip onto. And hobby chargers reliably detect the slight voltage drop that signifies end-of-charge, and support charge currents up to five amps or more.
Not that this is necessarily a good idea. Charge a set of ordinary AA NiCds at 5A and they’ll probably be too hot to hold at the end of the charge, and may "vent" – ooze electrolyte. High charge currents don’t charge these cells much faster – most of the excess energy is dissipated as heat. For these ordinary low performance NiCds, a charge current of 500mA is plenty, and some hobby chargers do not support this low a charge current. Why? Glad you asked.
While you’re at the hobby shop, check out the batteries that the hobby chargers are designed for. Model car packs are built out of special high current C-size cells, the best of which are made by Sanyo. These cells, with capacities of 1.4 or 1.7Ah, can handle repeated 20A discharges with peaks of 40A or more, and endure charge currents of five amps and higher. The super discharge capability isn’t necessary for digital camera applications, but the superfast charging can be handy. At 5A, a 1.7Ah pack can go from flat to full in less than half an hour (you have to put about 1.4 times the capacity of a cell into it to charge it). There are 2Ah cells as well, but they’re more expensive and not quite as tolerant of harsh treatment. All of these cells are NiCd; for a long time, no rechargeable CASIO NP-40 Battery technology even approached NiCd’s high current performance.
Nowadays, though, you can get sub-C NiMH cells with 3Ah capacity. They're the same size as NiCd sub-Cs, but weigh less, and can tolerate quite rough charging and discharging. There are lots of lower current NiMH cells with capacity well beyond that of NiCds as well; you have to be more careful charging them (they can't be charged as fast, and a charger that says it's only for NiCds is only for NiCds...), but they're a very sensible option for home-made packs.
The preceding paragraphs were my way of introducing you to my preferred solution to the Sony NP-FW50 camera battery problem – the big fat outboard battery pack. The simplest such pack is a D cell holder with alkaline cells in it. You can get a four D cell holder from any electronics store for a few dollars. The one in the illustration cost $AU2.30 from Jaycar. To connect the holder to the camera, you’ll need a lead that can plug into your digital camera’s AC adaptor connector. If your camera does not have such a connector – some very cheap ones don’t - you’ll need to hack something onto the SONY NP-BG1 Battery connections, or just get a better camera.
The connectors used by digital camera AC adaptors are, almost without exception, simple two-terminal "barrel" plugs. The easiest way to get a suitable lead is to cut one off an AC adaptor, but if that doesn’t appeal, you’ll be pleased to know that electronics stores stock barrel plugs in all sizes. There are several commonly seen sizes, and the 5.5mm outside diameter ones which are most popular have two possible inside diameters, so take the camera and/or an AC adaptor with you and get it right. A connector with too large an inside diameter can result in annoyingly intermittent power.
Making up your own cable also allows you to use stouter wire than is used in most plugpack leads. Pretty much any hook-up wire is thick enough to comfortably carry the current drawn by a digital camera, but thin wire is fragile, and a canon lp-e5 Battery pack lead will get twisted, trodden on, pinched in zippers and who knows what else. A good compromise between robustness, manageability and price is medium duty figure-eight speaker cable, or "zip cord", so called because you can "unzip" the two insulated wires from each other by pulling them apart. Check out the offerings at your local electronics store; it should cost you well under a dollar a metre.
It helps to have a nice long cable from the pack to the camera, so you can leave the "anchor" sitting on the floor and be able to pace about a bit. For field photography, I keep the canon nb-4l Battery in my backpack along with the other camera paraphernalia. Smaller batteries fit easily enough into a "bumbag" ("fanny pack", to Americans; in some other parts of the world, this sounds vaguely rude), but this can be rather uncomfortable with larger ones. You’d think having a power plug sticking out of your camera all of the time would be very cumbersome, but with the DC120 at least I’ve found my monster SONY NP-FM50 battery pack to interfere surprisingly little with shooting.
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