I have an interesting problem. I recently put my MK Hexa XL together with the MK power distribution board and BL-CTRL v2.0 ESCs. I'm running an Arducopter Mega system with oilpan and I modified the code to run the controllers on I2C. All that seems to run well. I've been working on setting the PID values and its getting fairly stable. I have one problem though. When I run the first battery, everything is fine. When I switch to the second battery, it does a backflip on takeoff. I relevel multiple times and no joy. It's almost like the direction of the gyro is getting flipped. I do tend to run the battery down if that has a contributing factor. I'm new to hexacopters, but I've been flying RC Helis for 35+ years. Any guesses as to what is wrong?