Thanks to you both for the advice. I will be at high altitude, so the weather will be cold -5 to 20 C. I will keep spare battery next to my body. I was worried because I used up a battery for one hockey game, but the camera was on and auto focusing for about 20 minutes out of the hour. In Peru it will be mainly scenery, so the camera will be on much more intermittently. I may take some astro photos, so I can see that consuming more power. As long as I have 2 batteries left for the last day, I will be happy.