I see lots of good lights here, i just have one problum, i bike at -20 to -40 below zero, so my battories in my current light dies before i get to my destanation, so i was wondering how theses do in cold weather, and how easy it would be to rigg a external battory pac (i am getting a new one, as my current one is dim, and from what i see, i think i can make one with drilling into the body and wireing it, hooking up my battory pac with a hedphone jack)

thanks in advance