I don't have one, but I am sure it is a bad idea. Smartphone batteries suck to start with and when you couple that with the cold, you just make it worse. My best guess would be about 3 hours of use before your phone was dead. Considering people cry about the LX-7s battery life, I can't see cell/flashers sticking around. Sorry for all the negativaty, I just do not see a single upside.