Power Capacitors
 

One topic I don't find much discussion on is the use of Capacitors to smooth out power delivery beyond power hungry Savox Servos.

Murfdogg has his Octane booster, and there are a few other similar products.

Can someone with Electronics knowledge (or experience) share a link, or an explanation on where Capacitors are needed, and whether these power boosters are the same as glitch busters?

I realize they basically create a reservoir of potential energy, likely between the battery and the ESC, to smooth the power delivery.

Why does this make things run cooler?
Do the sudden surges required by racing conditions build heat/reduce efficiency?

If Capacitors really are some magic bullet to improve performance so noticeably, why arent they built into the ESC already?

ESC do have them built in but they are limited for space

Input caps help lower ripple current

Excessive ripple current can cause ESC issues if you have high amp draw setups and lower spec batteries

A glitch buster style cap (plugs into RX) simply assists in holding up the bec output voltage so the receiver does not dropout under high servo amp draw, needed when the ESC's internal bec is inadequate

Cheers

Caps on the battery side of things allow the system to deliver more surge current (hard acceleration, for example) without the voltage dropping off (killing top speed, and causing heat.) I'm thinking the MurfDogg Octane Booster is something like this. A big bank of EDLC's or the like.

Caps on the BEC side do the same thing. Your servo tries to pull a ton of current out of a 3A BEC, and weird things will happen (Brownouts, glitching) when the voltage starts to plummet when the load exceeds the BEC's capability to hold the line up. This also causes heat, because the High Side Driving Transistor in a switching arrangement will be working overtime to handle it.

So glitch busters are made to plug into the BEC power port on the receiver, while Power input CAPs are put inline between the battery and the ESC?

Yep. For the ESC, connected with fairly short wires directly to the ESC for best results. As always watch the polarity.

From what I have seen, extra caps make fairly small differences. But it is important to at least use the cap that the ESC comes with.

Couple of diagrams on the input caps with a description

http://www.castlecreations.com/produ...-cap-pack.html


Diagram for an external bec if used instead of a glitch buster cap

http://www.castlecreations.com/produ...ec_wiring.html


Cheers

Talk about coincidence. I was searching for the same thing and out on my way to RS. Did a few searches and found some decent stuff for cheap.

http://www.radioshack.com/search/ind...capacitor&pg=1

Going to pick up a nice selection between 330uf and 500uf and experiment with them on my cirtix stock club.

The reading of the Novak power capacitor is educational, but I'm not sure where to buy the product as the link on the page doesn't seem to go to a specific product page.

I appreciate the diagrams, very helpful, thank you.

Next question, based on a search of Amainhobbies.com:

Do you need a different capacitor/unit if you change to a different cell count on your battery.

Competition runs almost exclusively 2s, but say I want to experiment with a 3s or 4s setup in the future, will the change in voltage have a dramatic effect on the capacitor?

Some of the power units I find get specific on what they can support, some don't, So I'm wondering how you can tell aside from comparing the voltage rating on the capacitor.

Castle input caps are rated at 50v

As Dave suggested I wouldnt be bothering unless you are experiencing issues

Large motors with huge amps draws and weak batteries are where they are needed

Cheers

Here is a link to our Capacitors & Modules. For specialty controllers, we offer replacement modules named for the esc; e.g. Mongoose. Our other modules are described based on the number of lipo cells used. You can use a higher-cell capacitor module on fewer cells---a 3S module on 2S, but not the reverse.

Our modules are replacements for externally soldered modules for all brands brush/brushless escs---not just Novak's.

Is there any reason I cant use the bigger Tekin Capacitors as glitch busters? They are 25v and 1850uf and obviously made for the ESC.

Regular Electrolytic Caps (Like what are used on the battery supply side) make poor glitchbusters on the RX Side due to the high-frequency noise that gets all over the 6v BEC line. HF Noise will barf an electrolytic cap in a hurry.

Things like the Novak Glitchbuster have ceramic caps and transient suppressors as well as Electrolytics to snub out high-frequency crap.

Aren't the input caps for the ESC switching noise, isn't that where the high frequency junk comes from?

The input caps are put in place to reduce voltage sag under hard draw. It lessens the blow you put on the battery's chemistry each time you hammer the throttle.

The only way to filter off high-frequency noise, via capacitor, is via small capacitors. Large capacitors, like radial electrolytics, don't have the frequency response required to snub the noise.

That's why things like Novak's Glitchbuster have small value ceramic (Fast) capacitors on the BEC side.

You don't want to put ceramics on the input side, because they are going to get mercilessly beat on under high current draw and all the ambient EMI/RFI. Big failure point.