Esc Capacitors

Old 09-04-2002, 07:44 PM
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Hi JesseT

Thanks for the input. I think the reason for using a smaller third capacitor is that with higher frequencies, the ESC output is much closer to DC and you need only a small capacitor to smoothen out the output. I don't know why the early ESCs you mentioned with 50-60 Hz would use a smaller Capacitor when they should be using a much bigger one for buffering.

Anyway, I'm going to look for bigger capacitors in my electronics junk box this weekend then I'lll try running with a capacitor bank of 4x4,7000 uF. I know I still have at least 4 from my last project. I'm still no good as a driver. I'll just see if the heating problem goes away with higher capacitance.


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Old 09-05-2002, 12:43 AM
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Originally posted by rough512
Hi JesseT

I don't know why the early ESCs you mentioned with 50-60 Hz would use a smaller Capacitor when they should be using a much bigger one for buffering.


No ment it just the other way around. Previously bigger motor caps were used.
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Old 09-05-2002, 04:42 AM
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Wouldn't 4x4700 be an overkill???

Last edited by TRF512; 09-05-2002 at 05:15 AM.
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Old 09-05-2002, 07:55 AM
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About the power booster: It was discussed here some months ago, but since then I've heard nothing and never seen one. Probably one of those TV-shop probucts.
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Old 09-30-2002, 06:17 PM
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Help!!
can any one help me.?.
I have a LRP Quantum comp (ESC),Ive been thinking of getting the option kit,for the small power capacitor,for my 1/12th mod,but i was hoping i could get one a bit cheaper from my local electrical store,could any one tell me what i ask for at a normal electric store,e.g what are they called and what size ,etc,i dont want one that is to big,hopefully the same size has the small one you get with the option kit..?...also the little black things that go on motors ?shkotty diode?what size/numbers etc etc do i get for modified motors,from an electrical store..?..
Thanx
Stevie
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Old 09-30-2002, 06:20 PM
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Old 09-30-2002, 09:37 PM
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Guys. Anyone had tried the Integy's 8800uF cap? Can I use that for my Novak's Rooster, Super Rooster, or GT7? Or If I use it for GT7, would it be much faster than using the stock high Cap from Novak?
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Old 10-14-2002, 03:55 AM
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is it recommended I use a capacitor with my Quantum Pro Sport even if it doesn't say so in the manual?
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Old 10-14-2002, 11:49 AM
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An R/C car works on 7,2 volts so a 10 volt or 16 volt capacitor like most ESC manufacturers suply is more than enough. Why is KO using 35 volt capacitors?
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Old 10-14-2002, 12:03 PM
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Originally posted by Stevie
Help!!
can any one help me.?.
I have a LRP Quantum comp (ESC),Ive been thinking of getting the option kit,for the small power capacitor,for my 1/12th mod,but i was hoping i could get one a bit cheaper from my local electrical store,could any one tell me what i ask for at a normal electric store,e.g what are they called and what size ,etc,i dont want one that is to big,hopefully the same size has the small one you get with the option kit..?...also the little black things that go on motors ?shkotty diode?what size/numbers etc etc do i get for modified motors,from an electrical store..?..
Thanx
Stevie
stevie further back in this thread i think jesse, dw and other discussed that the caps you find at your regular electrical store are not high frequency caps, which is what your stock and mod motors are running at. so i suppose you would probaly burn it up with the high switching frequency of your motor. if you want one i would suggest you go with the worlds option kit, though im no electrical engineer.
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Old 10-14-2002, 01:30 PM
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The small Capacitors that are used on the motor are there to reduce electrical interference from when the poles in the motor become uncharged, and there is a "Fly back" voltage. All caps are high frequency. They let high frequency through, while blocking low frequency. (ever see a crossover unit for home or car audio?) The larger capacitors used on the battery side is used to store electricity. Just like the HUGE caps used in high end car audio, the capacitors on the battery are there to give a small burst of current, particulary while accellerating. It make no difference on your top speed however. Also, using a larger cap on the batt. will give you a shorter run time, although not too important with todays high capacity batteries, it would make a small difference with 2000's. And for racing stock, you don't need a huge cap, because the motor never hardly draws more that 25-30 amps (usually) and for the most part, the battery can keep up with that. It helps the ESC run cooler because in order to deliver the same wattage, when the voltage gets lower, it has to draw more amps.
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Old 10-14-2002, 08:45 PM
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For schottkey diodes SD830 works wwell, its made by diodes inc.

GIve me a day or so to look up suitable power caps.
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Old 10-15-2002, 05:46 AM
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Pit Crew:
Have you ever seen a high frequency home audio cross-over? Audio frequencies are not by any standard "high frequency". All capacitors have an complex impedance changing with the frequency. This consist of capacitance, inductance and resistance. In a capacitor the inductance and resistance are tried to minimize, but are never zero. So, what is generally meant with a high-frequency capacitor in this context? It's a capacitor with a relatively low impedance at high frequencies, meaning it's resistnace and inductance are low. You said a capacitor is a high pass component. Well yes, but when the frequency is further increased it starts to block the current again. Ceramic capacitors work with much higher frequencies than electrolytic capacitors, but try to find one with 1000s of uF.
The capacitor is used, not to help supply current under acceleration, but to help supply current for a single current pulse that the ESC operates with. Same goes for 1:1 scale car amplifiers, they also work with a pulsed current.
The capacitor makes the battery operate more efficiently, so the only way runtime is diminished with is by utilizing more energy.
Please also read the older messages.
BR/ JesseT
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Old 10-15-2002, 06:26 AM
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Does anyone know the answer to my question (I think 4 posts ago)? Thanks.
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Old 10-15-2002, 07:44 AM
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A capacitor with a higher maximum voltage rating typically has a lower impedance. This means that with the same numbers for capacitance, the one with a higher voltage rating will give out it's energy faster. On the other hand, a capacitor with a higher voltage rating is also larger by approximately the same ratio. So, in my opinion it's better to use instead a larger capacitor with higher capacitance, but... I don't know. It's not a big difference. Perhaps they got those cheap ;-)
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