I have never had too much interest in that sort of thing until i started looking for options for my icefishing toys(did i say toys...i meant tools!!). One of the biggest reasons i had to do something, was the discharge rate in extreme cold. Even in -10C, my standard AA rechargables were losing too much to the cold. I had to do something....the once a day charging was a pain in the ass on a 7 day fishing trip, and i wasnt about to head to a heavy lead battery (like a lawnmower battery).