RE: Wattage IC-15A premature BEC cutoff
ESCs, especially simple brushed ESCs tend to either work, or smoke. It's far far far more likely that you either have a bum battery or a bum motor. The battery may be capitulating under the "stress" imposed by the motor.
BTW, what are you trying to spin with that motor? Trying to spin too much prop is another likely culprit.