You are trusting to luck if you use a BEC. I have a web page all about them here: http://homepages.which.net/~paul.hills/Emc/Bec.htmlhttp://homepages.which.net/~paul.hills/Emc/Bec.html. That page also has a section showing how to use a rechargeable battery that can be charged from the main battery when not in fighting mode.

Good luck!