I’ve experienced the same Battery problem with my Evo. Luckily the drop in battery power happened right after takeoff so I wasn’t to far out. I had enough elevation to return to my takeoff point even with the app showing no time or charge left on battery. It dropped from 100%, to 50%, to critically low in under a minute. I removed the battery and noticed it had 1 blinking light still on back of battery. Mysteriously, after sitting in my drawer for a few days I checked it again and it had 3 solid lights and 1 blinking light on the back of the battery. I turned on my Evo and it’s showing a battery capacity of 80%, how is that possible, Bad Battery!