NiCads (nickel/cadmium) and nickel metal hydrides are rechargeable batteries that last between 8 and 12 hours and cost up to 10 dollars each. Alkalines are disposable batteries that last between 25 and 30 hours and cost about two dollars each. Because extreme temperatures can drain battery power, it is recommended that you always carry a spare set of batteries. In cold weather, attaching the battery pack to your belt under your jacket can help keep batteries warm and dry.
