Esc Capacitors

Old 07-22-2002, 02:40 AM
  #61  
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Jesse,

you say that you can't use power caps on reversing speed controllers. Well I have a GM V12R (reversing) and that comes with a power cap??

thanks

sanj.
www.schumacher.clara.net/powercap.htm
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Old 07-22-2002, 02:50 AM
  #62  
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pardon 4 asking,...but jus exactly do u solder the cap on the esc and wat r the advantages n disadvantages?
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Old 07-22-2002, 04:16 AM
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Hi Ijnek...

that's what we're trying to find out

Let's wait for Jesse though...

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Old 07-22-2002, 04:12 PM
  #64  
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Sorry for not replying earlier.

Yes you can use an esc cap on a reversing esc. It connects across the battery leads so there is no danger of reverse voltage. If you connect it across the motor leads - pop, hiss... The little caps on the motor are non-polarized so they don't care about reverse voltage.

The purpose of an esc cap is the same as that of an airbox on an IC engine. Esc's operate on pulse width modulation of a certain frequency. The power is ALWAYS switching on and off very rapidly. A capacitor is a electrical damper so it smooths out those pulses, thus making the throttle feel "smoother". The other thing it does is provide stored energy for rapid discharge. Batteries simply cannot provide the momentary 60A+ spikes that a mod motor can draw at times. A capacitor stores energy upon connection with the battery and dumps it when demanded. It generally takes a lot of experience to be able to feel these things, and I've had IFMAR Worlds A-main drivers tell me that they can't feel the difference between 680uF and 3200uF.

As for a Schottky diode, the full name is Schottky barrier diode. They are designed to be able to withstand quite a bit of reverse voltage. We actually run them in reverse. When the motor is on power, the diode is reverse biased and acts like an open circuit. When the motor is off power, it takes the back emf generated by the spinning armature and bypasses the brake circuit for the most part and effectively shorts across the motor (which is what your brake circuit does). This keeps your brake fet(s) from overheating and that's also why you want to mount it as close to the motor as possible (to bypass as much of the current as possible). The current flow generated by this back emf is much smaller than the drive current when the throttle is applied. That's why when you hook up a Schottky backwards (or forwards depending on how you look at it), you fry it because it cannot take the amount of drive current.

Last edited by ruf; 07-22-2002 at 04:15 PM.
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Old 07-28-2002, 11:07 AM
  #65  
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Does anybody know were I could get a replacement capacitor for a regular cyclone?
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Old 07-28-2002, 03:38 PM
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you can get one here at stormer hobbies
https://www.ssl-stormerhobbies.com/c....pl?pn=NOV5675
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Old 08-25-2002, 10:53 PM
  #67  
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I tried connecting a 50v 100uF capacitor to the battery side of my LRP F1 Pro Reverse esc (reverse disabled of course). I then set my throttle trim upwards until the wheels started rolling. I tried connecting and disconnecting the capcitor. No change in speed.

So I connected it on the motor side and yes.. the wheels started going faster!!!. I replaced the 100uf with 1000uf. The wheels started going faster!!! I removed the caps, the wheels went back to their old slow and jerky revolution.

I was going to make the connection permanent but then I noticed the caps started heating up until its too hot to touch.

I don't get it. Connecting the caps on the motor side is just like connecting a filter capacitor on the output side of a power supply rectifier. On my power supply the caps never get hot like this. The caps should have only smoothed out the pulsating DC from the ESC same as the filter caps (on my power supply) smoothens up the rectifier output.

The way I see it, the capacitor is conducting the DC pulses like AC, question is, this does not happen on power supplies operating on 50-60Hz. Is it because of the ESC's higher operating frequency?

Can the electrical engineers here help me on the theory please?

Thanks.
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Old 08-26-2002, 01:57 AM
  #68  
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Sorry for my mistake earlier. I was thinking of Shottkys. Sure you can use a capacitor with a revesible ESC. As for the last post, it might be the negative voltage spikes it can't tolerate or just it's too high parasitic resistance. On a switch-mode power supply the output voltage across the capacitors does not fluctuate too much meaning there's not that much current going through the capacitors. With an ESC+MOTOR combination the capacitor is most likely used for much higher currents. I might try this some evening.
BR/ JesseT
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Old 08-28-2002, 01:09 AM
  #69  
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hm plz do post the results of the expriment that u r doing with the caps .....
would like to know more
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Old 08-28-2002, 01:43 AM
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Hmmm...

Results?

2 burned capacitors so far because I forgot to disconnect the capacitor when I enable the reverse function of the ESC.



As for the real results... Increased speed was observed on partial throttles. My theory is that those spikes from the ESC are smoothed down into a level usable to the motor. The only problem is that the capacitor heats up....

Will try some more experiments as soon as I get hold of newer capacitors...
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Old 08-28-2002, 06:25 AM
  #71  
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any effects on the esc????

btw whats the frequency for ur esc...
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Old 08-28-2002, 06:37 AM
  #72  
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rough...the reason you did not notice any difference on the battery side was that you were in effect adding capacity to the battery pack, the biggest difference you should notice is when you actually drive the car...esp. on a tight road course, the cap. will smooth out the AMP draw peaks and provide a little better acceleration out of corners.
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Old 08-28-2002, 08:09 AM
  #73  
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LRP F1 Pro Reverse

Voltage Input: 4-7cells (4.8-8.4V)
On-Resistance: 0,0041 ohms
Rated Current: 270A
Max. Current (30sec): 100A
Cont. Current (5min.): 55A
Rec. Motor Limit: No Motor limit
B.E.C. Output Voltage: 5.0V
B.E.C. Current 30sec.: 1.6A
B.E.C. Current 5 min.: 0.6A
PWM Frequency: 2500Hz
Brake, Drive-Control-System: EMK
Reverse Operation, switch off: yes
Multi-Protection-System: yes
Adjustment: Digital


No effect on the ESC just yet.

Myclod:
I'm too much of a novice to notice any improvement with the addition of the capacitor when it comes to the track. I'm too busy trying not to hit the walls
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Old 08-28-2002, 09:43 PM
  #74  
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hm........... do try out the cap on motor side and tell me how it feels ....
i am using keyence v zero extreme esc and ... not sure if it needs one
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Old 08-29-2002, 03:22 AM
  #75  
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Probably a higher frequency will be easier for the cap if it's placed after the ESC. My cyclone works at 22 kHz (or close), so I'll try it in the near or distant future... ;-)
I keep getting inquieries about the zapper, so perhaps I'll put something up here in the future too.
BR/ JesseT
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