The Problem is NiMH and most recharges like LiPo have poor performance in cold conditions and is the reason I never touch the things for most of my needs such as head torches and avalanche beacons.
Try using rechargeable at -20*C and things can get very dangerous, even life threatening. Alkali batteries are relatively good with cold temperatures.
The other problem with most rechargables is they have less predictive power curves and power output tends to suddenly plummet, Alkaline batteries are much more linear and predictable, so when say a head lamp starts t fade slightly you know you are OK with a regular battery but with a rechargeable it is hard to predict how much longer you wil have usable light but it certainly wont be nearly as long as with an alkaline.
Try using rechargeable at -20*C and things can get very dangerous, even life threatening. Alkali batteries are relatively good with cold temperatures.
The other problem with most rechargables is they have less predictive power curves and power output tends to suddenly plummet, Alkaline batteries are much more linear and predictable, so when say a head lamp starts t fade slightly you know you are OK with a regular battery but with a rechargeable it is hard to predict how much longer you wil have usable light but it certainly wont be nearly as long as with an alkaline.