I am using a Tiger battery 4S 6000mAh 35C and I set the voltage failsafe in Mission Planner at 14.0V (3.5V per cell as suggested).
The problem is that from 50% of the discharge of the battery (3000mAh used), if the current request increases above 50A, the voltage drops down the limit and the drone goes in Fail Safe mode, returning to launch. I could decrease the minimum voltage, but this is not recommended in manuals and forums.
Do you have any suggestion?
The "strange" thing is that in my case the voltage drops below 14V only if the current consumption is really high for some demanding maneuvers, but as soon as I go back to cruise speed, the current consumption goes to 20A and the voltage goes back to 14.5V at least.
Is there any way to avoid this?
I'd like to know this answer too. Having the exact same problem. Was loitering in gusty winds and after about 2 minutes the low voltage light started flashing and the beeper started sounding. I checked the battery on the ground and it read 15 6 V and I have the fail safe set to 14.5v. All Arducopter says about it is set it for 10.5 volts but that's way too low for a 4S battery. My other 2 quads run the old APM 2.6 and and never had this problem. My new Hex runs the Pixhawk.
I have the ONBO 6000 mah battery and it is excellent thus far. I have used the battery about 10 times and so far it provides more flight time than the stock 5200 mah by about 10 min. Takes a bit longer to charge too obviously but definitely worth snagging these up when you can get your hands on them because they are scarce!
I would imagine just like any other manufacture, the warranty from DJI would be void if there were a malfunction with your phantom because these batteries aren't authorized or manufactured by DJI.