Just want to add to what Zoossh has mentioned.
I haven't had any problems with charging batteries in these areas. Even in really ulu areas in Tibet, I've been able to find places to charge betteries. I think it will only be an issue if you are going for long-term trekking (over a week or more). Remember also that cold weather drains battery life too. In really cold situations, I will keep my camera batteries in my jacket pocket, close to my body heat.
