I am in the process of assembling a quad using an APM2.0 as the flight controller. The craft also has a Futaba 7-ch receiver, a Mini-OSD, an EZ-20 Sonar Sensor and a 3DR Radio for telemetry. The whole system runs on one or two 4S Lipo batteries. There is a 1.5W Video transmitter and camera, but they are powered by a separate 12V regulator off the raw (14V) battery output.
The 5V loads, APM, RC Rcvr, Mini-OSD, 3DR Radio and Sonar are powered off one of the ESC BEC's. The ESC's are all Hobbywing 30A with 5V/2A BEC's. I've measured the current draw on the 5V BEC and it varies between 250mA and 300mA with the quad idle (Disarmed). After 2-3 minutes in this state, the ESC/BEC that is powering the 5V load becomes nearly too hot to touch. The other three ESC's are at ambient temperature.
To see if it was just a defective ESC, I switched which ESC/BEC was powering the 5V load. The heat moved with the load.
My question: Is it normal for an ESC/BEC with a 5V load of 300mA (and a rated output of 2000mA) to get hot just sitting on the bench? FYI, this quad seems to fly just fine. If I hadn't touched the hot ESC during some tweaking, I would not have noticed the anomaly.
Thanks for your help.