Ask the Teaboy

Q: Lithium Ion or NiMH (nickel metal hydride) - What's the difference?

A: After the megapixel question, and the zoom question, the next most important factor to consider when buying your digital camera is arguably that of whether to buy a unit that can take lithium ion or NiMH batteries. The importance of this question is increased when you factor in that digital cameras consume a lot more power than their mechanical film ancestors did.

In the evolution of batteries for portable devices there have actually been three kinds to date:

Nicad (nickel cadmium)
NiMH (nickel metal hydride)
Lithium Ion

Nicads have gone the way of the Dodo. By today's standards they are heavy, and their problem with the 'memory effect' (where you can't get a full charge from the battery any longer because you forgot to run it down flat before recharging) means we're not sad to see them go.

There are pro's and con's to consider with the remaining two kinds of batteries:

NiMH (nickel metal hydride):

Although there are other shapes and sizes of NiMH batteries, most digital camera consumers will only see them in their AA sized form (you know, the one's your Mini Maglight runs off). The obvious advantages of having a camera that takes AA batteries is the availability of replacements. Whether you're in London or Lagos - you're going to find AA batteries far easier than any other. If your NiMH AA batteries run flat, and you have nowhere to charge them, you can always run into a corner store somewhere and pick up a set of use-once AA batteries. There-in lies the only real advantage of AA NiMH batteries - that they're the same shape as regular non-rechargeable AA batteries!

If we compare NiMH batteries with Ni-Cads there are added advantages (higher capacity, lighter, and much less prone to memory effect), but compared to the newer Lithium Ion batteries the above paragraph is about it.

Lithium Ion:

Lithium Ion is the latest development in battery technology. They do not suffer from a memory effect at all, and are even lighter (by up to 35%) than NiMH (which was lighter than NiCad), and are also more environmentally friendly as they have no toxic components like Cadmium or Mercury. Last but not least - they last longer!! A camera running on Lithium Ion batteries will last much longer than one using comparible sized NiMH batteries.

The disadvantage of Lithium Ion is that if your battery runs out, and you have no power outlet (or time!) to charge it, then there's not a lot you can do. Most digital camera lithium batteries are specialised enough that you'll only find them in a camera store, and may be impossible to source when you're travelling in Tibet!

Having said that - even when travelling there are ways to benefit from Lithium Ion without being caught with a 'dead camera':

Carry a spare! When you consider that the extended life of a lithium ion battery means you can generally make it last all day, a spare will make it a certainty. At night, back at the motel, you can charge them both. If you're going to be away from a power outlet for several days, perhaps have more than one spare, and practise energy saving habits like using the viewfinder rather than the LCD screen for composing your shots, and turn your camera off immediately after use. The writer recently managed a 4 day hike in the mountains with only two lithium ion batteries. And yes, I took lots of photos!
If you travel a lot, consider purchasing a camera that can take BOTH lithium ion batteries AND a standard type battery (several of Nikon's Coolpix cameras for example can take the supplied lithium ion battery as well as the standard CR25 use-once battery).

So, you choose - the longevity of lithium ion, or the availablity of AA's?