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Discussion Starter #1
Hmmm Looking for alittle input here on an Idea... I know we all put or have built on Capacitors on our motors but anyone ever tried upgrading or adding a bigger capacitor to your motor??? A Cap stores power right?? and releases its stored energy when there is an applied power..?? Wouldn't this be great??? If you could have that extra bit of power everytime you hit the trigger.. anyone have any information on this???

Thanks

James
 

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are u refering to the little caps that keep the motors from glitching, or the bigger one that all the new speedos use.... hank has some good ones on the site. for speedos...
 

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As the saying goes, you don't get nothin' for free!

Any juice you store in the caps has to come from somewhere. In this case the battery. Plus, it can't store a higher voltage then the battery can supply.

The main and really only use for large power caps is to keep the voltage of your battery pack from falling too low when using low turn modified motors. The medium sized cap I sell gives you a little larger safety margin when stock and mild mods.
 

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When you install one of the large electrolytic capacitors on your speed control it goes across the battery terminals. They are polarity sensitive, meaning they have a Plus and a Minus. When you let off of the throttle, the motor is “backing down” and is generating a small amount of electricity. This is stored in the large Capacitor and is released when you hit the throttle again. It is not much but it is some.

If you put a polarized capacitor across the motor it self, it will blow. I know, because it hooked one up on the speed control that way by mistake one time. LOL The non-polarized capacitors that are used across the motor (in any size) do nothing but filter off voltage spikes that cause glitches from the positive to ground and do not store any voltage.

Be carefull with adding too large of a capacitor across the speed control, they can actually cause a throttle lag if they are too big.
 

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i had also heard that if u do not lift the cap doesnt re charge.. making it pointless... like by us in stock and 19t we never lift in the turns.... is this true????? anyone????
 

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ARCing occurs the "most" durring breaking.

Arcing is what is the root cause for our RF noise...
The more ACRing that occurs, the more RF noise is generated.

RF Noise = BAD when your using RF signal to control the car.

The caps on the motor are used to help "SHUNT" the noise to ground.

Without getting to deep:
Caps pass AC and block DC....

Think of motor Whine on a cheap car radio...
i.e: audible tachometer :)
 

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burbs. Yes this is true. An electrolytic capacitor is a small battery, the only why it can discharge any voltage is for it to be charged and the only way to charge it (in the application we are talking about here) is from the motor and/or battery. When a D.C. motor is being driven, as in when you let off of the throttle and the car is slowing down, it turns into a generator and creates voltage that will help charge the capacitor. When you get back on the throttle, the motor will discharge it just like it does your batteries.

Nothing is free though and there is a catch but it applies more to low turn Mod motors. The larger the Cap that you put on the Speed Control the more it takes to charge it and the little throttle “blip” that is done in the corners will usually not do it. The only way it will completely re-charge itself is to draw off of the source that it is across….the battery. So, you get more punch off the corner with a large Cap because it acts like a very small but extra cell in the pack but in the long run it is less efficient because it has to constantly be re-charged during the run.

In Stock, you hardly ever let off so it doesn't matter. In 19t, the high timing and the occasional “lift” does cause a lot of arcing and I would run a smaller Cap on the speed control, something like 680 Mf. Open Mod speaks for itself.

No matter what your application is, I would recommend the smaller Caps (3) on the motor because all motors are “noisy” with RF and can cause radio interference.
 

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I'll have to disagree. You place the power cap across the pos and neg terminals of your battery. As soon as you hook up the battery, it charges the power cap. Want to test this? Unhook your motor and hook up your battery, then unhook the battery... now short the terminals of the cap (it'll spark) or measure the voltage if you don't want to short it.

A cap has a LOT less resistance then a battery, they will discharge almost instantly. When high amps are drawn, the voltage in the pack drops below the voltage in the cap, the cap then helps keeps the voltage high. Since the discharge of the cap is so quick, this is mostly helpful when amps draws are in the 50+ amp range. Low turn mods need a larger cap because they can draw high amps for longer lenghts of time.

Yes, braking/coasting does put a slightly higher voltage out, but the cap can never have a higher voltage then pack that powers it since it is in parallel with the battery pack.
 

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What you say is true but today’s speed controllers have a regenerative feature that is cause when the motor generates voltage that is put back into the pack, which the capacitor has become a part of. You are correct in saying that the pack is what charges the Cap though. I should have worded it different.
 

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The pack and the cap is in parallel, therefore the pack and the cap have to have the same voltage... that is simple electronics. While during a regeneration spike, the cap may have a slightly higher voltage, the ultra low resistance of the cap means it only takes miliseconds (maybe even microseconds) for the cap to discharge back into the battery.

Anyways, this is a good discussion and something I may have to test since I have access to the Data Recorder. Do a test of the voltage drop under high amp load with and without a cap.
 

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You know, that would be a REAL good thing to see. Frankly I have never thought of it LOL. Not to settle this because I am sure you are right but just to see how much that little booger is really doing.

I have had so much to do lately at work that I have not had the time to look for a newer computer and work with mine. Too much to do and not enought of me LOL.
 

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Discussion Starter #17
Hank... Please pass the results out.. I'm interested to see what the Cap is capable of doing and if its worth adding... I picked some Caps up today.. and going to try adding it to my ESC for the races tomorrow... Hopefully see an improvement....

Thanks

James
 

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i honestly doubt in any way there will be any improvement... i have run both with and without and cant see a bit of difference.... i havent run one in forever.. but i run stock. maybe u s a dfference in mod or 19t but i doubt it... u would see super sized caps on every speedo out if it was that way...
 

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If you are running stock, I don't think you will see much difference. But in 19t and especially Mod., I would not run without one. It would be interesting to see the real results to see just how much it is doing though.

It's 5:45 AM. Time to make that long drive to N.C. See you guys tomorrow. If you have a local track, SUPPORT IT! Not having one SUCKS!
 

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First, the large capacitor goes on the battery side of the ESC to act as a charge tank. If you put a large capacitor on the motor side of the ESC, the motor and capacitor will fight for charge and acceleration will decrease.

Here is an article saying why a power cap is needed.
http://www.rczone.net/modules.php?name=News&file=article&sid=373

I just got this power capacitor. 10,000uF!!! 2 for $10.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3190750340
I have one on each of my micros.

You can get an even bigger capacitor if you want.
 
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