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Old 11-10-2001, 01:54 AM   #31
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ok will check manticore
i said that because i felt that my car has less punch and top speed after i installed my 14500uF 16v cap
i m not using a cap anymore till i get one from a ESC manufacture itself

the 14500uF cap is from matsushita/matsuhita/matasuhita/matasushita corp cant remember spelling but i know its a big company.
and its also LOW-ESR/impendance one
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Old 11-10-2001, 10:06 AM   #32
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matsushita=Panasonic in the U.S. or National in Asia and Europe. Caps are caps as long as you get comparable tolerance to the stock cap. There is nothing special about the cap the the esc comes with. They put that bs in the instruction about having to use their "special" caps so you don't experiment, cook your esc and have the mfr fix it under warranty. If you need a new cap, write down what the stock one is or take it to your local electronics supply store and buy a comparable one. 4700mfd is 4700mfd no matter who makes it, as long as you compare electrolytic to electrolytic (which is what the esc comes with.)
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Old 11-11-2001, 03:10 AM   #33
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hm ... u say its of no difference but actually there ARE SOME SERIOUS DIFFERENCE...... i have personally checked em out

and there are a few types of cap which is not usable although the UF rating is the same ...u can hook on but it will make the car move real slow

i just bought a GM cap at about US$12 for 1 cap
the rating is at 8600uF and 16V it does not slow down the car like my other rubycoms cap which is also rated at 8600uF 16V
the GM cap actually makes my car punchier ...when ever i needed the extra OOmPh....
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Old 11-11-2001, 01:57 PM   #34
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I'm fairly sure that the GM Cap is a Panasoinic FC series. That is what i was told when i e-mailed Ralf Helbing about it. Hence that is what i use and i agree that it gives more punch.

The difference lies in the Impedance of the cap. Cheeper items are high resistance, which is no good at all.
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Old 11-12-2001, 01:40 AM   #35
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thanks matt
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Old 11-12-2001, 07:08 AM   #36
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Well.... see there are so much interests and conflicting ideas here.... I just bought a new ESC and I will be checking this out just for fun.... maybe my electronic engineering can help me to understand this more.....

From designing many power supplies, instantaneous gain in power (amps) is usually gained on the battery side, as you can get caps with much lower internal resistance than a battery....

Something to play with this week!
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Old 11-12-2001, 07:30 AM   #37
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When up rating the caps (of the same uF value), the only real specifications to look out for are generally:

Your voltage rating for the Cap can go higher but never lower than the original or the specified operating voltage of the system.

Temperature cooefficient, if it is rated at 85 degrees C, uprate it to 105 degrees C.

Generally the lower the ESR the better the characteristic (debatable).



If you really want to "tune" the power supply of any system, remember BIGGER is NOT always BETTER. There is always a "sweet spot" value which will make the system work the best. It depends on so many variables (battery impedance, ESC circuitry loading, motor loading and motor bandwidth....) that the easiest way to find the "sweet spot" is by trying a range of them and "see" if you can "feel" the difference.....
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Old 11-12-2001, 11:17 AM   #38
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This is how i had the theory explained to me.

The Cap has lower internal resistance (esr, Impedance) than your cells. Hence it will discharge into the speedo before the cells will, hence more punch.

I guess it probably isn't quite as simple as that, but it does make a little bit of sense if you think about it.
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Old 11-12-2001, 01:14 PM   #39
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Different brand/series/ and configuration of capacitors will determine how that cap will perform. It's impossible to state that one cap is better than the other. Caps have various internal resistance at different frequencies, voltages, current, temperature, etc, etc. You could have one cap work very well on LRP and not work well at all on a Novak, because they might run on different frequencies, which means they are operating at different internal impedance. Also, it will affect charge and discharge characteristics. Not all caps are created equal. Note that Novak has changed their caps 3 times within past 1 year. They are different, but probably have similar characteristics. You don't HAVE to use "their" caps as they tell us to. If you want to use the same cap, order some from Digi-key for $1 each instead of paying $6. I was planning on "pre-zapping" the 1 Farad cap before running the car. If not for any useful purpose, for fun and entertainment.
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Old 11-12-2001, 11:58 PM   #40
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Matt W, I've been on this subject earlier too, but once again: That's not the reason they are used for. You're right, there's more into it.
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Old 11-26-2001, 07:39 PM   #41
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Mattw,

can you tell me what is the color of the GM Cap. And what's the value ? Thank you


Quote:
Originally posted by MattW
I'm fairly sure that the GM Cap is a Panasoinic FC series. That is what i was told when i e-mailed Ralf Helbing about it. Hence that is what i use and i agree that it gives more punch.

The difference lies in the Impedance of the cap. Cheeper items are high resistance, which is no good at all.
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Old 11-26-2001, 08:25 PM   #42
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I have a cap manufacture making speical size cap for me.
I have tried from 8600 to 33,000, they all reacted differentlly to the motor wind and to differnt ESC used.

Some of them made huge improvement in punch, but it doesn't mean the bigger the better. You need to find a sweet spot. Since there are so much variable, like the batteries and the motor condition, I haven't found a right combination yet.

Anyone else have any suggestion.
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Old 11-27-2001, 09:16 AM   #43
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Samples finally arrived from the manufacturer. I'll try them this weekend. You're right, you have to find a sweet spot, it doesn't work just anywhere.
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Old 11-27-2001, 11:56 PM   #44
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I hope you know what you are doing. Just bear in mind that the speedos operate with square wave signal, which creates an infinite Fourier-searies! No speedo operates with just one frequency. At full throttle there is no frequency what so ever, and a capacitor will have no effect at that point, except that it might be cooler because of the capacitor (you were right in that point). Can someone please justify this sweet spot theory? Isn't a lower Z-value always better?
Best regerds, JesseT
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Old 11-28-2001, 09:59 AM   #45
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I'm an electrical engineer. I don't claim to know everything, but I do know a thing or two. And actually, most of the ESCs operate at a fixed frequency. Some of them let you choose what frequency to use(such as Cyclones). The way it works is that like you said, it works off of square waves, but by varying the duty cycle of that wave, it changes the speed of the motor. There are many FETs inside the ESC and they are switched on and off at the frequency you run it at. When it changes the duty cycle, it basically changes the ratio of ON versus OFF. They do this by pulsing the gate of the FETs.
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