If you are going mountaineering you have to be aware of the impact on your light of the freezing cold that you will encounter at high altitude. Even if you have one of the best mountaineering headlamps, you will soon find yourself sitting in the dark if you don’t take the cold into account. This is because no matter how good your lamp is, it will do almost no good with frozen batteries.
The first thing that you have to worry about is the simplest and that is running out of batteries completely. It may sound stupid to remind people of this but you need to carry a set of spares. You also have to be aware of the fact that flashlights and headlamps have an annoying habit of switching themselves on and running down their batteries while they are tucked away in your backpack. If you have something such as the new Petzl MYO XP Belt headlamp then there is a smaller risk of this happening because the switch is protected by a little cover that helps stop it from turning on in your bag. If you don’t have a lamp with this feature then you have to follow a much simpler, if more labour intensive method. Simply remove one of the batteries from the torch and keep it somewhere safe and dry. That way there is no chance of the lamp coming on and running down your batteries.
Many people will tell you to put it back into the battery compartment with its polarity reversed. DO NOT. A battery that is inserted the wrong way can draw charge from the others in the battery pack. It could burst and spill corrosive liquid or emit explosive gas.
Okay, so if you now have ensured you have spare batteries and that the ones in your light have not run down unintentionally, your next worry is cold because nothing shuts down the chemical reactions that go on inside normal Alkaline batteries quite like cold does. Below freezing the amount of light you get will drop off considerably.
Although these batteries are in fact designed to keep operating down to about -18 C their service life is considerably shortened as you can see from this graph produced by Energizer (above).
There are two solutions to this. One is to use Lithium batteries, which have a working range down to about -40c. Not all headlamps can use them. The ordinary Petzl Tikka XP can’t but the Petzl Tikka XP2 can. The other great thing about Lithium batteries is that they are about 30% lighter than normal Alkaline batteries.
Another approach to dealing with cold batteries is to keep them warm. Headlamps such as the MYO XP Belt have the batteries in a remote battery pack (usually a belt pack). The idea here is that you can slip it inside warm clothing to keep it from freezing. Follow these simple steps and your mountaineering headlamp should keep going strong, even when the mercury is dropping.