RE: What is the pupose of ESc capacitors?
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I didn't set out to 'dis' you - I hadn't seen these particular parts before but I stand by my statements. By the way, I do have a formal education in electronics - I am a junior engineer for a company that makes high horsepower brushless motors and controllers (up to 150 horsepower). I am currently laying out a PCB for a high energy DC-DC converter (more than 50A at over 300 volts) so I know quite a bit about trace widths. It is true that you want to keep trace widths as high as possible (less voltage drop means less heat buildup in the board). Normal design procedures call for decoupling capacitors (usually 0.1 or 0.01 ufD) as close as possible to the device using the current but it is common practice to put the big filter capacitors off in the corner of the design and away from any signal electronics to keep down EMI noise problems.
The caps in these links are quite pricey (three times the cost of the ones I mentioned earlier) but the real problem lies with their intended usage. These caps (and the SMT ones I referred to) have their ripple current rated at 120 hz - they are intended for filtering a full wave bridge for a 60 hz line transformer. The ripple current capacity falls off rapidly as you rise in frequency because the transitions in voltage are much faster so the current either sinked or sourced is far higher in a shorter period of time. Add to that the fact that a PWM application is in effect a square wave output (a straight switch on / switch off relationship which causes huge transitional currents compared to the relatively low slope of a sine wave) so therefore the ripple current spec falls off very quickly and the heat buildup goes up exponentially as frequency rises. The 1500 uF caps I referred to are rated at 100khZ and are intended and designed for switching applications and can take the abuse that PWM filtering dishes out.
The other problem with SMT caps is that you have all of that weight suspended on two small surface mount pads. Given the impacts that an RC car endures you have a good chance of ripping the pads off the board with an impact rendering the ESC useless (if you don't short it internally and burn the battery down with it). There is also a large amount of both radiated and conducted electrical noise created by the caps and having them in close proximity to your control circuitry is asking for trouble aside from adding another heat source inside of a tiny little sealed box.