Wow again? I got an email requesting some clarification to this link so here you go.
Power caps explained. Again. (Futureal keep this posted someplace maybe the tech section)
This may sound Like a Novak Add or something, but that is were my experience is. The statements apply to most ESCs.
The power cap on a Novak ESC is there to prevent the ripple current that is created by the ESC from damaging itself. It's not really for any full throttle response, as when the ESC is at full throttle, it is not switching, it turns into a "junction" only. It would be like soldering the wires directly from the battery to the motor. Full power is full power is full power.
The Power cap is actually there for partial throttle operation. When you are using anything other than full throttle the ESC is switching very fast. A Novak ESC switches faster than most (not the drive freqeuncy, but the switching used to create that drive frequency) so the problem is more severe. Due to the high rate of the switch process a ripple current is created. This means the voltage is flowing into the fets so hard and fast, that when the ESC switches to off, the current continues to flow and heats up the parts. This is probably an over-simplified explanation, but you get the idea right? So the Power Cap absorbs the ripple current, prevents the heating of the ESC and feeds the stored voltage back to the motor on the off cycle. That inturn creates a much cooler ESC and vastly improved mid range throttle response.
You can easily test this, but running your motor at partial throttle, then removing the power cap, the motor will slow down, when you reconnect the power cap the motor revs up a little.
Power caps are not for full throttle acceleration, I can see why that mistake is often made, it makes a little sense, but is not correct. They may have an effect on it, but are not there for that reason.
After that people want to know why you have to use a special Cap. Reason for that is that the capacitor has to be the correct "performance". If the cap is the wrong ESR value it will not do anything in the system, so it doesn't provide any protection. Problem is capacitors don't spec the ESR, it is usually indicated by the manufacture in a "series" or line of parts. The Radio Shack cap will damage your ESC.
Next question is usually about schottky diodes.
A schottky diodes is an electronic one way valve for voltage. When your motor free spins it creates voltage that is fed into the ESC. A schottky prevents that voltage from getting to the ESC. As a side effect you get more consistant breaking. They are still required even if you don't use the brakes, becuase the are stopping damage that happens every single time you lift off the throttle. Schottky diodes also increas motor voltage in a similar manor to power caps. My understanding of that isn't as clear, but similar RPM gains are noticed.
Currently Novak has been developing our ESC dyno. We have been working on ESC comparisons and what does what. What we have found for sure, is the problem does not come from the ESC or what it's doing, motors from only a couple years ago are more efficient and create much smaller issues. Today's motors may seem great, but the truth is they are less efficient overall. There are always acceptions so don't jump on me if I've said something you don't agree with or have different experience.
Anyfurther questions directly to me, please shoot me an email.
Thanks
Charlie
Novak Electronics.