If not a poorly inserted batt, my belief the next likely cause is a bad cell or even a dumb *** smart battery. I say this off my experience with 3 P2's and soon to be P3 pilot. And of course we are going to fly over water, we fly where the beauty is. My favorite is the nudist camp or White House lawn (kidding). All 3 of my P2's have severe crashes due to the failure of the battery as described above. The most recent this week gave me some ideas to research. As before on the previous 2 battery failure crashes, battery was firmly inserted and this time was hovering only a few feet from me for the purpose of running batt down to approx 50-60% since I had not used it on the weekend and may be weeks before using again. All normal until 79% and 11.1v**, suddenly it went to 10%-10.8v, batt icon was empty and flashing, red LEDs flashing and going down fast. Being close I reached to catch and just as quick the voltage shot back over 11v, didn't notice what the percentage was with the chaos, but everything returned to normal seemingly. As I stepped back it immediately went back to before with batt now showing 10.6v and less than 10%, as I caught it I continued to apply power to watch the battery readout. It would alter between a reading of 11.1 or .2 or .3v running strong, to 2-3 seconds later back to 10.4 and falling, with motors going to auto land. Each time the batt icon would show 3/4 full to blinking empty. The back and forth almost seemed like a loose connection with the abruptness of the changes, but now each swap in v readings on the lower end keep getting into the range I thought this thing would not do. It hit 9.8, 9.6, 9.3v and somewhere along here the motors finally shut off. I charged it back up later and after the second flashing light went to solid green, it stopped charging, but pressing the batt button shows a full charge. One of the other failed batt did the same after reaching the third solid green light, can't remember details of the first batt. The Assistant SW showed no indication a problem with the batt, but the cell voltage readings were off a little; 1 3880 2 3815 3 3879. This mean anything? Today I will remove the cells, and try to rebuild using the best cells from my P2 batt infirmary. I'm not sure how to pick the best or identify the bad ones, they all are reading close in volts (smart cap problem?)
With amount of money invested in the pricier drones, in my opinion the battery does not give me the confidence I need my investment will come home tonight (like my ENRON investments). I wonder if a electronic device that can automatically kick in with a batt failure with just enough batt juice to get something like a P2 or 3 say an extra 50-100' for an emergency landing. But thats added weight and cost, plus you add another failure potential. I like the idea though.
**Some values I am not 100% correct, but it definitely got down to the low 9s, thought it shouldn't;t even run that low.