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Old 01-19-2003, 01:24 PM   #1
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Default Power Capacitor benefit

Guys;

I have an older Tekin G-9 ESC that does not require a power capacitor like some of the newer ESC's do.

What would be the benefit of adding one (or drawbacks) and EXACTLY where should I add it in the circuit.

Thanks,

Last edited by popsracer; 01-19-2003 at 01:56 PM.
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Old 01-19-2003, 01:29 PM   #2
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i use schotty diodes's on my car it helps reduce arking between the brushes and the motor all you do is solder one end to the positive tab on the motor and one to the negitive tab. if you use mabuchie 540's then use 2 diodes it seems to go a little faster
that's an idea i should test it on a dyno
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Old 01-19-2003, 02:02 PM   #3
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Default schotty diodes's

fasterdanu;

The Tekin ESC has a built in schotty diode and the instructions recommend NOT adding a second one at the Motor. There is however no mention of using a Power Capacitor in the instructions anywhere and one was not supplied with the ESC.

Some people have said you will gain punch by adding one (Power Capacitor), but I've also read the exact opposite would happen. Thus the reason for my question.
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Old 01-19-2003, 02:18 PM   #4
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The g9 already has a capacitor board built in which is why no external power capacitor is required. You could add a power capacitor but it probably wouldn't make much difference.
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Old 01-19-2003, 05:26 PM   #5
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I've heard two different schools of thought. The capacitor is suppose to decrease the glitching effects of the motor by absorbing the spikes in the capacitor. I've also been told that with the capacitor installed and with a charge, it adds that charge to the voltage of the battery. In effect adding a few millivolts to the motor causing the motor to spin faster. The capacitor is installed across the battery pos (+), and neg (-) on the ESC.
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Old 01-19-2003, 06:16 PM   #6
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Correct me if I'm wrong, but a smaller cap gives you more efficiency, but less punch, and a larger cap gives you more punch at the sacrifice of efficiency.
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Old 01-19-2003, 07:25 PM   #7
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Quote:
There is however no mention of using a Power Capacitor in the instructions anywhere and one was not supplied with the ESC.
Good replies, please keep them coming.
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Old 01-19-2003, 07:48 PM   #8
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Quote:
Originally posted by skibum989
Correct me if I'm wrong, but a smaller cap gives you more efficiency, but less punch, and a larger cap gives you more punch at the sacrifice of efficiency.
\
not exacly like that.
the smaller ceramic capacitors are called 'noise suppresors' ..reducing glitch caused by high speed motor rotation.
the large ones are called 'Power-capacitors' bcos it adds power...theoretically.actually it gives a little more punch/power when u release throttle to a point where supply voltage is lower than voltage across the power-cap....thereby inducing the power-cap to discharge....ie give power.
there would be a sort of short time where the charging up of the power cap would result in delay of throttle response..but it's hardly noticable.
suppressors just absorb the reverse/irregular charges coming out of the motor.
power-caps are normally 10000 micro-farads while suppressors are like 0.1 micro-farads.they operate independantly...ie they dont affect the operation of each other.
i hope im correct..read this somewhere else.also correct me if im wrong.
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Old 01-20-2003, 02:10 AM   #9
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Not quite accurate.
The power capacitor works at any partial throttle setting not just when releasing the throttle. Why would you want to increase motor speed under braking anyway?
You are right about the suppressors though.

A speedo works by rapidly switching motor current on and off. When you push the transmitter stick the amount of time the current is turned off reduces until you reach maximum when the current is on all the time. Ideally the waveform produced by the speedo switching on and off would be square. However in practice the current is gradually ramped on and off.
The voltage a battery can supply reduces with increasing current. What the capacitor does is charges up in the part of the switching cycle when current is low and battery voltage is high. It then discharges in the next part of the cycle when battery voltage is low and current is high. This means that the voltage stays more constant.

Basically the capacitor gives more power at low throttle settings. It also helps the speedo run cooler.
It makes no difference to top speed.
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Old 01-20-2003, 05:29 AM   #10
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http://www.schumacher.clara.net/powercap.htm

when you get on the throttle hard, the voltage fromt he batteries drops, the powercap reduces the voltage drop (or ripple). the graph on the above link explains it a bit better

sanj
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Old 01-20-2003, 05:52 AM   #11
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Default Stock motors?

Will a power cap make any difference on stock motors, or is it only worth it with mods like 10-turns?
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Old 01-20-2003, 06:34 AM   #12
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Any idea wat kind of capacitor are use for the reciever.
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Old 01-20-2003, 07:02 AM   #13
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Sanj
I think The capacitor is far too small for your theory to be correct.

capacitance = 10,000 micro farads = 0.01 farad
charge stored by cap = capacitance * voltage

0.01*7.2 = 0.072 coulombs.
(1 coulomb is equivalent to 1 amp for 1 second) but the capacitor will only release this much energy if it is connected to a 0 volt supply. As the cap is connected to a battery the energy released will be much less than this. Bearing in mind the initial current draw of a motor can be around 80 amps the current released will be relatively insignificant.
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Old 01-20-2003, 07:36 AM   #14
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popsracer: The Tekin G series had everything they needed built in. I have never heard of anyone adding a power cap to their tekin. Even the pros like Masami who used to use them to win world championships never bothered to add one. So it would seem to me that if they didn't see the benefits, then there were none to be gained.

I think you should leave it as is and just run it baby!
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Old 01-20-2003, 09:16 AM   #15
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Darkseid is correct... don't add anything to the Tekin G9, it's easily the best speed control you'll ever run just the way it is.

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