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Old 11-03-2004, 11:54 PM   #11
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Caps are useful with the radio equipment, some people use them in line with the battery connector (if there's an ESC in use) and sometimes, with certain fet servos, on those connectors too, they help keep the power drops from being too nasty (which can cause glitching, because when the voltage drops below a certain threshold, it's along the lines of changing the constants of the universe).

As for the diode usage for reverse, yes, it's only meant for braking to avoid frying the ESC with the reverse voltage that comes in (being generated by the motor). Novak makes a 25amp one, which survives a lot better than the original ones did.

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Old 11-26-2004, 10:12 AM   #12
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Okay, found a decent link with info on these regarding RC use... Take a look...

Artificial intelligence is no match for natural stupidity.

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Old 11-26-2004, 10:55 AM   #13
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This is the information from Sanj's Yokomo RC Homepage as linked above

You often see people at clubs with large cylindrical objects attached to their speed controls. You may be wondering what these are and what they do. This should shed some light!

Do not confuse these capacitors with the small variety found on motors to suppress interference!

Why do you need a power cap?
Whenever you get on the throttle hard, the voltage output of the batteries falls drastically, in some cases down to 1 or 2 volts (see graph below). This is called a voltage ripple and is not really very pleasant for the speed controller. A voltage ripple causes the speed controller to overheat and in turn you get less power to accelerate with.

The graph below demonstrates what happens if you get hard on the power at time = 0 seconds. After about 0.04 of a second you get a massive voltage drop from the batteries. If you use a power cap this voltage ripple is smoothed out significantly, the value of the power cap dictates how much smoothing occurs

Power Caps and Reversing Speed Controls
It doesn't matter if your speed controller has reverse or not, the addition of a power cap WILL NOT blow it up, it will cause it to run cooler and should increase its life span.

Buying Capacitors
LRP and M Troniks both sell capacitors as add ons for their speed controls. The caps sold in these kits are no different from the variety you find at your local electronics store, the only difference is the price and the sticker! Any High frequency Low impedance Capacitor will work fine on an RC speed control. The cap must also have a working voltage of 10v or greater.

The capacitance of the capacitor is how much charge it can store (measured in Farads or microfarads), This value is important as it dictates how smooth the voltage ripple becomes. For simply smoothing out the voltage ripple so your speed controller doesn't get hot a 1000uF cap is sufficient. If however you are running a low turn modified motor and want lots of extra punch, then 10,000uF is about the size you want.

You can get capacitor sizes bigger than 10,000uF, but as they the capacitance gets bigger so does their physical size. Here is my friend's car with a 22,000uF capacitor (the big blue thing!).

There are a couple of disadvantages with caps, one is there size and mounting them, they may be small but space on cars is limited.

The other problem is there charging time. Capacitors when discharged do take a fraction of a second to charge up, in this period you have reduced power. The bigger the cap the longer the charging time.

The cap has markings to distinguish the positive and negative sides, the leg nearest the grey stripe is the cathode and should be soldered to the -ve from the battery, the other leg should be soldered to the +ve from the battery. For neatness these solder connections are often made at the speed controller because the wires are closer together.

Is a cap worth it? Absolutely its the best £3 mod you can buy. You gain acceleration, keep your electrics in better condition and increase the lifespan of your speed control. The time taken to charge the cap is negligible.

I would however not reccomend buying a MTroinks Power Cap(£15) or LRP world kit (£20), they are overpriced and the caps at your local electronics store are probably of better quality too! I don't usually praise companies but I'll make an exception, GM sell power caps too but at only £3!
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Old 11-28-2004, 07:43 PM   #14
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Im wanting to try a power cap......i took out an electric today and realized with a 15Td my brakes suck.
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Old 11-28-2004, 08:33 PM   #15
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Sanj works for Rolls Royce. I used to run Yokomo. Haven't talked to him in ages man. I have a design for an mr4tc top deck from the surikam car. small world
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