I have the 655T. The Lith/ion batteries in mine are great and I keep a AAA battery pack as back-up in my pack but have never needed it. If I leave it on all day long, using the radio, I'll use 50% of the power - that's sun-up to sun-down. If I only turn it on when I need it, I can go almost a week on one charge. I believe the 650 has a larger screen, just no camera. I would go with the larger screen if I had it to do all over again.