I was asked yesterday which AA batteries, of the non-rechargeable kind, are best for use in cold climates. Well, the answer is quite simple at the moment - and it doesn't matter if it's a hot or cold climate, the answer is the same - Energizer ultimate Lithium batteries.

These use Lithium battery technology rather than Alkaline and so they last much longer.  In fact, Energizer claim they last up to 8 times as long as ordinary batteries.

For cold weather performance, they can't be beat either - a working range of -40°F to 140°F means they should keep going even when you're starting to freeze up...or melt down!It's the reason NASA uses these batteries to power on-board cameras and video cameras for the Space Shuttle Discovery.

If that's not enough for you, they have a 15 year storage life so you can stock up when you find them cheap (their only downside is they're more expensive than ordinary batteries) and keep them for when you need them. 

For years, I've been using NiMH rechargables. While I still do when I don't need better performance, more and more I'm finding I use these Energizer Lithiums, especially in flashguns - they recycle quicker and you get more flashes between battery changes. 

There's one thing you need to be aware of though - how little they weigh. When I fisrt started using them, I kept picking up flashguns and thinking they had no batteries in! If you think I'm joking, look at the images below - in both pictures there are four batteries on a set of weighing scales. Where the four NiMH rechargable batteries tip the scales at 106g, the four Litium batteries weigh in at a scant 54g. That's so very close to be half the weight. So if you're travelling, you can carry twice as many batteries, that last longer and not suffer any weight penalty. 

If you're US bound on your travels, just take a peak at current FAA guidelines. Back in 2006/7 they were limiting the number of Lithium batteries that could be carried on a plane in the hold or hand-luggage. The latest rules I can find (linked above and from April, 2008) suggest that in hold luggage you can have batteries installed in a device provided it is locked off and in some form of protective case. For hand-luggage you can carry spare batteries as long as they are under 100 watt-hours of power and are either in original retail packaging, or if they're loose, they have the terminals taped and each battery is packed so it can't short with another - separate plastic bags or in a container that keeps them safe for example.

The long and short of this is that since each Lithium battery will provide around 3 watt-hours of power, you can carry c.33 in your hand luggage at a time.  Unless you are planning on importing AA batteries on an industrial scale, you should be fine as long as you follow the precautions.