In the last flight of my big jet there was an issue that i cannot fully explain. I use the mercury with 2x 2s 3150mAh LiOn cells (rated for 30Amps). In the first 2 minutes of the flight i got a low battery warning on the TX (from one of the RX batteries) but i thought the trigger level was a bit to high and it was only for 1 second so i continued the demo. 2 minutes later i deployed the flaps on a bit faster then normal speed and got the low battery warning again, but the plane started a dive also from which i could not recover by pulling up, meaning there was not enough power in the elevator servo's (normally with flaps it stays level). This scared the ehll out of me and removing the flaps gave me elevator control again. I landed quickly without any issues.
Then i looked at the logs (sadly the RX voltage was not logged) and looked at the battery voltages. Battery 1 was a nice level line that showed 7.0-7.1V for the entire flight. Battery 2 showed about 6.9V with a large dip to 6.3V the same time i lost the elevators. So it was clear battery 2 was the issue.... but why did i loose the power to the servo's? Both batteries charged the same amount back in (2200mAh) so batteries were used through the regulators. How do both regulators work? Are the outputs in parrallel? Why was battery 1 still at a good level but the output voltage not? Could regulator 1 be overloaded and loosing voltage when regulator 2 had not enough from the battery? Normally the PB heatsinks are cold after a flight.