Can anyone please post a realistic battery runtime? In the manual says "Up to 4 hr. in camera mode" but in my case at 2 hours battery is almost dead. I use 720p btw and record only during radar activity, which is assumed is better for battery life. It is possible my device is defective? My trainings is over 2 hours many times and i want that valuable device all the time with me. Thank you very much.