9XL & Mamba Max Shut down!

[BrianG]

If you use low battery voltage, like 6-10v, the internal BEC is fine. Any battery voltage over that and the ESC will heat up faster just because of the BEC. Whether it will fry the ESC or not is hard to say. Most should have thermal cutoffs to prevent self-destruction, but there have been instances of the internal BEC frying.

In short, I'd use an external BEC for anything over 6 cells/ 2s lipo for best results.