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Originally Posted by squeeforever
It isn't a coincidence. The use the same kinds of internal BEC's (can't really remember if there a Linear or not) and that type they use in all the different ESC's can only handle so much heat before they go poof.
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Yeah, most I've seen are linear.
The more cells you use, the more power is wasted by heat on the BEC. The power dissipated on the BEC is (v_batt - v_bec) X bec_current. v_bec is usually around 5-6v. So, if you are using 12 cells (~14.4v) and your servos are drawing an average of 2A, that is almost 17 watts the heatsink has to dissipate. If you only use 8 cells (~9.6v) with the same 2A servo draw, that's only a little over 7 watts. Since the ESC heatsink is usually pretty small, it needs all the available surface area just for the motor controller. Any added power is just going to make it heat up faster/more. If you can't afford or don't want to use a digital UBEC, at least hook up a simple outboard linear regulator.
The internal surface-mounted caps are usually not electrolytic types and aren't quite as sensitive to voltage. But like MetalMan said, the external caps can't really be used to judge the ESC voltage capacity. Maybe the manufacturer got a really good deal on a bunch of 50v caps and decided to use those instead of the "proper" 35v or 25v caps. Also, all those FETs have a max working voltage as well, and unless you can read the part number and get a datasheet for them, there is no way to really tell.
But if you want to experiment, and have deep pockets, then more power to you! :)