Hi I just reread your letter again and I spotted something that happened to a friend of mine. He had an BEC ( battery eliminator circuit) plus he used a separate receiver battery, instant spark and smoke and good bye one ESC and BEC. You cannot connect a receiver battery and BEC connection to the receiver at same time. If you only used the extra receiver battery to program the ESC but did not have your receiver plugged in that is a different situation. I have stopped using BECs in my larger airplanes and only use an ESC and a separate receiver battery. Much safer that way. After I lost a good airplane due to bad cut off voltage I gave up on using a BEC. What plane are you working on and how much does it weight and what is the wing span and area? Those facts will tell me a lot as well. Norm