Esc Capacitors
05-12-2002, 04:53 PM
#47
Tech Adept
Chances are a Radio Shack Cap will hurt you. You need a low inpedence, high frequency cap, these are expensive as far as caps go and radio shack dont carry them.
05-20-2002, 06:24 AM
#49
Tech Regular
I can't think of an easy way to check it out. If you just take randomly some type of capacitor with the correct numbers, in 95% of the cases it's unsuitable for RC ESCs.
05-22-2002, 02:53 AM
#50
Tech Initiate
High frequency caps (and schottkey diodes) are available at reasonable prices from the following vendors:
Mouser Electronics (www.mouser.com)
Digi-Key Electronics (www.digikey.com)
I recently looked up a Panasonic brand rated at 4,700uf/16v/105c for $2.52 each. This particular part is designed for high switching frequencies as used in switching power supplies. Both places offer price breaks starting at quantity 10 or more. Both also offer free catalogs which I suggest because it makes looking for specific parts easier.
If anyone has a Fry's Electronics (www.frys.com) nearby, they are also a good source for parts.
Mouser Electronics (www.mouser.com)
Digi-Key Electronics (www.digikey.com)
I recently looked up a Panasonic brand rated at 4,700uf/16v/105c for $2.52 each. This particular part is designed for high switching frequencies as used in switching power supplies. Both places offer price breaks starting at quantity 10 or more. Both also offer free catalogs which I suggest because it makes looking for specific parts easier.
If anyone has a Fry's Electronics (www.frys.com) nearby, they are also a good source for parts.
Last edited by Babblefish; 05-22-2002 at 02:56 AM.
06-29-2002, 02:16 AM
#52
Tech Apprentice
Originally posted by JesseT
Overkill in the size is quite common as it seems. However the type of the capacitor is much more important. It should be a high frequency or a low-impedance capacitor. Changing to a huge capacitor of the wrong type can be a step to worse from the stock capacitor.
On the other hand, no capacitor will make you win races.
Overkill in the size is quite common as it seems. However the type of the capacitor is much more important. It should be a high frequency or a low-impedance capacitor. Changing to a huge capacitor of the wrong type can be a step to worse from the stock capacitor.
On the other hand, no capacitor will make you win races.
Hope u can help me with this.
A big thx.
07-01-2002, 03:34 AM
#53
Tech Regular
Lets put it this way. The capacitor should have a low impedance at a high frequency. The impedance varies with the freqency. I'm sure they know at the electronics shop. At least they should know. It's not sure if they have any though.
BR/ JesseT
BR/ JesseT
07-01-2002, 04:32 AM
#54
Tech Apprentice
Thx for the info. 
I'll make a trip to the components shop when I can find time, at least I hav a better idea of wat to look for now. But how to find out whether they had given me what I ask for?
(guess I hav to take their word for it)
A big thx for ur time and info
I'll make a trip to the components shop when I can find time, at least I hav a better idea of wat to look for now. But how to find out whether they had given me what I ask for? (guess I hav to take their word for it)A big thx for ur time and info
07-18-2002, 03:21 PM
#55
Tech Rookie
Sounds silly but Do I solder the postive leg to the postive motor wire and the negitive one to the negivite motor wire?
07-18-2002, 04:23 PM
#56
popee - you solder the big esc caps across the battery leads. The stripe is negative and it goes to the negative battery lead.
For everyone else, try to get a Panasonic/Matsushita HFQ series or FC series cap in 16V rating. The FC replaced the HFQ about a year ago. Masami also happens to use the largest FC cap available on his 12th scale: 8600uF! Rubycon and others also make low impedance caps, but I can't remember the codes. I think ZC? I'd have to go look it all up again.
Also, make sure you get 16V rated caps. Fresh off the charger, our batts have close to 10V. If you'll notice, the new Novak caps are only rated for 10V. There is almost no margin making for a very non-robust circuit. From an engineering perspective, this is ridiculous. From a marketing perspective, it's ingenious since Novak now sells a lot more caps. Remember how long the old ones used to last? Guess they got tired of that.
For everyone else, try to get a Panasonic/Matsushita HFQ series or FC series cap in 16V rating. The FC replaced the HFQ about a year ago. Masami also happens to use the largest FC cap available on his 12th scale: 8600uF! Rubycon and others also make low impedance caps, but I can't remember the codes. I think ZC? I'd have to go look it all up again.
Also, make sure you get 16V rated caps. Fresh off the charger, our batts have close to 10V. If you'll notice, the new Novak caps are only rated for 10V. There is almost no margin making for a very non-robust circuit. From an engineering perspective, this is ridiculous. From a marketing perspective, it's ingenious since Novak now sells a lot more caps. Remember how long the old ones used to last? Guess they got tired of that.
07-18-2002, 05:51 PM
#57
Tech Rookie
Very true its just a marketing scheme. Ive nearly graduated in Electronics Engineering Degree, I jsut wanted to double check with the Wiring of the Cap. Im using a standard low impediance, high Frequency Capacitor from Rapid Electronics rated at 10v, 10,000uF. Ive jsut been trying it out tonight in my losi XXXt, seems to give my trinty speedgem more punch, saying that the punch on my ESC is quite low setting. its helps marginaly, but its just a marketing scheme to sell a capacitor, thats worth Less than a dollar fo9r over $20,
07-18-2002, 09:38 PM
#58
Originally posted by ruf
popee - you solder the big esc caps across the battery leads. The stripe is negative and it goes to the negative battery lead.
popee - you solder the big esc caps across the battery leads. The stripe is negative and it goes to the negative battery lead.
Please dont take this differently.
If this is the way to wire the caps, then why is there so much fuss about not installing caps when using reversing ESCs? Why do you still need a high frequency Cap?
I thought the caps are wired in parallel with the motor to smoothen the pulses coming from the ESC. The schottkies on the other hand are wired such that the large inductive kick from the motor is soaked/routed away from the ESC.
I am also confused with these Low impedance, High Frequency capacitors... Lower capacitance means high impedance for high frequencies right? Higher Capacitance is lesser impedance for High frequencies.
Anyway, right now, I use neither Caps or Schottkies as I am using a reversible ESC ( novice driver, really needs to reverse off the wall
) . But when the time comes for me to install a cap, I would look for a capacitor big enough to smoothen the ESC output but not too big to rob power from the motor every time I go from brake to throttle...You've got more experince on RC, please correct me if I'm wrong...
Last edited by rough512; 07-18-2002 at 10:14 PM.
07-19-2002, 03:09 AM
#59
Tech Regular
The electrolytic capacitors are polarized components and don't tolerate reverse voltage. Therefore you can't use them with reversible controllers. Same goes for sthottkys.
The capacitor is wired in parallel with the batteries, not the motor. The purpose of the capacitor is to effectively lower the internal resistance of the battery pack when using partial throttle.
A real-life capacitor always has capacitance, inductance and resistance. The combination is the impedance. A low impedance cap usually has lower resistance and impedance. This makes it able to operate with higher ripple currents and frequencies.
The capacitor is wired in parallel with the batteries, not the motor. The purpose of the capacitor is to effectively lower the internal resistance of the battery pack when using partial throttle.
A real-life capacitor always has capacitance, inductance and resistance. The combination is the impedance. A low impedance cap usually has lower resistance and impedance. This makes it able to operate with higher ripple currents and frequencies.
07-21-2002, 07:37 PM
#60
Originally posted by JesseT
The electrolytic capacitors are polarized components and don't tolerate reverse voltage. Therefore you can't use them with reversible controllers...........
The capacitor is wired in parallel with the batteries, not the motor.
How's this??? If you wire the capacitor across the batteries, then that capacitor will never be in danger with reverse voltage no matter if the ESC is reversing or not.
The purpose of the capacitor is to effectively lower the internal resistance of the battery pack when using partial throttle.
I'm having trouble thinking up of an equivalent circuit diagram to support this. As far as I know, viewing it from battery, the capacitor will appear only as an added load during power on ( more accurately, when you connect the battery assuming the capacitor was thoroughly discharged). The only way of lowering the internal resistance of the battery is by altering it at the chemical level. (Reverse pulse charging is said to help)
The electrolytic capacitors are polarized components and don't tolerate reverse voltage. Therefore you can't use them with reversible controllers...........
The capacitor is wired in parallel with the batteries, not the motor.
How's this??? If you wire the capacitor across the batteries, then that capacitor will never be in danger with reverse voltage no matter if the ESC is reversing or not.
The purpose of the capacitor is to effectively lower the internal resistance of the battery pack when using partial throttle.
I'm having trouble thinking up of an equivalent circuit diagram to support this. As far as I know, viewing it from battery, the capacitor will appear only as an added load during power on ( more accurately, when you connect the battery assuming the capacitor was thoroughly discharged). The only way of lowering the internal resistance of the battery is by altering it at the chemical level. (Reverse pulse charging is said to help)
