I have tried to take care of my batteries by, down to 8% every 20 cycles, storing at 50%, rarely ever flying below 30%. Today I had a new experience. Flying along as usual, battery life 60%, and the starts to decend. I was at about 200 ft so had time to react. Up throttle and landed it safely after maneuvering around pine trees and down a hill. Was in panic mode so didn't observe the battery life data during the descent. After landing, I caught the bird and looked at my fps data, battery at 4%!! This is the first battery purchased, 97 cycles, battery life 91%, (recharged to) charge 53%, 3.849, 3.852, 3.850V. I then though, maybe it is the P2 acting strange. Flew with another battery, went down to 15% and started to auto land as it should. I did this test twice, the second time with an older battery bought about the same time as the failed battery. This time I did notice that the older battery started to rapidly decline way before it reached 15%. So, with older batteries, I'm not going to take them to low or I might run out of juice fast.