A while ago I bought this switching BEC from HobbyKing http://hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=10313&Product_Name=Turnigy_5A_(8-40v)_SBEC_for_Lipo_ for a project that never materialised.
A few weeks ago I built a new glider, a 2.6m Discus I intended to use for aerotowing. When I was looking for a suitable receiver pack I found that the glider balances perfectly with a 3s 1800mAh LiPo. Remembering the BEC I bought earlier I thought that should be a perfect setup good for a weekend of fun without having to recharge the receiver pack. Assembled everything and had a few successful flights.
Last weekend I decided to swap the Spektrum AR6200 receiver for a Weatronic receiver. The main reason was that I wanted to use my shiny new Weatronic telemetry system I received just a day earlier and the secondary reason was that I'm slowly changing over from Spektrum to Weatronics.
Ok, done that, reprogrammed everything. Not very difficult as the glider only uses ailerons, rudder, elevator and a tow release. Then the stir-test on the bench (moving all the sticks together as fast as I can) and the Weatronics module started complaining loudly about link loss. Looking closely at the receiver I could see the red led flashing for a split second. Took the memory card out of the Weatronics module and checked the log on my PC. And there it was... stirring the sticks created peaks of about 3.5A for a very short time (rather big metal geared servos) and every time this happened the 5A rated Hobbycity BEC dropped the voltage enough to cause a reboot of the receiver!
Went then back to the Spektrum receiver and tried to reproduce this issue. Indeed, the Spektrum receiver rebooted as well. Only difference was that the Spektrum receiver did it silently but the loss of control was significantly longer than with the Weatronic.
I have never noticed anything in flight but usually my stick movements are not that wild like on the bench test I also never noticed the Spektrum receiver flashing (indication of brownout) but the receiver is not visible from the outside and I usually switch it off without looking at it so it may have happened.
The fix was easy, the Hobbycity BEC went into the bin and was replaced with an Align BEC rated at exactly the same 5A but actually performing to it's specification.
The moral of the story.... If it's too cheap it probably doesn't do what you expect and never, never trust Hobbycity BECs