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Old 08-29-2005, 04:31 AM   #196
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Quote:
Originally Posted by PitCrew
I made no mention of energy evaporating... My point was the same as yours, that energy is converted. In an RC car, its converted to heat and motion.

When you let off the throttle, if there has be voltage depression, the cap will charge to whatever the cells voltage is (it will only ever equal the voltage of the cells) when you hit the gas, the voltage drops due to the load on the cells, at this point the capacitor discharges into the circuit as well- thereby for a short period of time delivering MORE power to the motor than would otherwise had gotten there if no cap was used. This power has to come from somewhere- it comes from the batteries. Therefor, buy using a capacitor in an on and off demand, the net energy delivered to the motor is going to be higher than without using a capacitor. In looking at your simple laws, you can't get something for nothing. More power to motor in same time period with cap, then with no cap means the battery is discharging faster. Less run-time.

With the audio amplifier example I made, I was referring to a capacitor on the input power (12v) not the output. Maybe you are not familiar with high end car audio? They use HUGE caps mostly on the sub amps to maintain power under huge bass hits (big load). When big bass hits, its makes a big load, and can draw down the voltage. Then to maintain the same wattage, as most amps have circuitry to do this, they draw more amps. Then they get hotter, and have more distortion.
About the amplifier. My opinion is that any product that doesn't work as intended without external help isn't well designed. As a sidenote I find the whole notion of thousand watt amplifier and cutting up car interior to fit big speakers stupid. My car comes with 12 speaker sound system that is designed by sound experts exactly for that car, with sound reflections from windows and interior calculated in a computer. This system far exceeds all my needs with incredible clarity and sound quality. Adding big subwoofer to this system would be hilarious.

I see your point in energy use. But capacitors store very little energy, and with good batteries the capacitor only "kicks in" to help the batteries under full acceleration from standstill or very low speeds. This only happens maybe two or three times each lap, the extra energy used by the motor is so little that it doesn't matter, you can charge the cells 3 seconds longer and have the exact same runtime.

PS. ESC on full throttle is continously on.
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Old 08-29-2005, 10:20 AM   #197
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Quote:
Originally Posted by andsetinn
About the amplifier. My opinion is that any product that doesn't work as intended without external help isn't well designed.
This is the type of blanket statement/opinion that I'm talking about. You need to qualify and clarify this. Almost everything (be it electronic or natural) around us function as intended WITH external help... -JB
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Old 08-29-2005, 04:49 PM   #198
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Quote:
Originally Posted by JayBee
This is the type of blanket statement/opinion that I'm talking about. You need to qualify and clarify this. Almost everything (be it electronic or natural) around us function as intended WITH external help... -JB
Actually if you read this thread I think you'll find the example I made.

Let me help you. Here is the quote:
Quote:
Originally Posted by Andsetinn
I personally think the ESC software is badly designed if it "needs" capacitor, but that's my opinion.
The reason I think this, is because it's easy to let the ESC software monitor the input voltage and reduce throttle for those milliseconds that the input voltage falls. EOR.
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Old 08-29-2005, 07:07 PM   #199
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Hi all,

IMO again.

I would like to clarify one thing.

Actually with better software not. The is a chance for the fets inside the ESC to experience the ripple stage. BTW, the ripple happen not only when you pull the full throttle, but also when you make a throttle. But in full acceleration, the problem is obverious. Because in real the battery experience a suddenly extract of energy is happening in the begin of each "On" cycle of the esc. For example. if the ESC is operating in 2000HZ. Then in one second, the battery will experience a suddenly extract of large energy 2000 time. But each time the period is not long. The effect is accumulating. But in full throttle, energy is really being taken out, the battery become more easy to get into the ripple state.

With complicated software design, system will monitor the status and apply the energy from whenever it gain to prevent this happen. With a simple software, it parallel a cap which fit the operation frequence and live it alone. .
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Old 08-29-2005, 11:37 PM   #200
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I sure hope nobody is confusing placing a large capacitor on the wires that lead to the motor........

We are discussing a capacitor wired in parralel with the battery.

As far as the capacitor goes anyway, it will only give you an advantage on the very onset of acceleration, about the first .05 - .10 seconds. After that, the capacitor will be at only the same voltage as the battery, and will provide no real benefit. ONce you are up to some sort of speed, it is no advantage, or real disadvantage for that matter. Except the weight, which they hardly weigh anything.

In respect to the amplifier for audio and such, I would like to note that any high end home audio system like Harmon/Kardon or Denon will have very large capacitors on the power supply. One way they acheive high volume levels while maintaining clarity. Using a capacitor is not necesarrily "outside" help. Merely their size prohibits their installation INSIDE the ESC case. Easier to find another nice place to put it.

Furthermore, wouldn't the use of 12 speakers, audio technicians, and computer modeling for sound contour and reflection be "outside" help. It takes all that to get the 12 speaker system to sound as good as a 4-6.1 speaker system (speakers plus woofer) with a fairly inexpensive high power amplifier? Hmm just thinking.
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Old 08-30-2005, 12:21 AM   #201
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My DCM System does... point made/taken PitCrew -JB
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Old 01-22-2006, 11:27 AM   #202
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Instead of putting capacitor to ESC......, why not putting it where it need most like receiver ?

Somebody put a capacitor to receiver's batt input ?
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Old 01-22-2006, 07:13 PM   #203
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Quote:
Originally Posted by asw7576
Capacitors is helpful to stabillized the volts under current draw or perhaps smooth out the current flow, but it doesn't make any motors go faster / produce more rpm.
BINGO, You right! You get my vote...
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Old 01-22-2006, 07:17 PM   #204
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Quote:
Originally Posted by asw7576
Instead of putting capacitor to ESC......, why not putting it where it need most like receiver ?

Somebody put a capacitor to receiver's batt input ?
For years everyone I knows uses them on the reciever.
There called sutter stoppers from Novak.

Also, Spectrum requires the use of one on the reciever if your running 4 cells.
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Old 01-22-2006, 08:22 PM   #205
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I can't read this no more!!! Its killin me Brian cells..!!
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Old 06-03-2006, 09:17 AM   #206
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not to bring this up again.. but what would be a good cap for the mamba 25 esc with the 8000kv (considered a mod in micros) i currently use anywhere form 6-7 cells on a continuos bassis, and occasionally i may use up to 10 cells.. .
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Old 02-11-2007, 08:49 PM   #207
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Default HOw do you know it's low ESR and high ripple capacitor

I have read all of this thread but no one mention how the caps consider as
1. Low ESR (max. impedance in 20 deg. celcius / 100Mhz)...
2. High ripple (mA rms in 105 deg celcius / 20~100Mhz) ....

Can anyone come with the numbers for both no. 1 and no.2 above....

Thanks....
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Old 02-15-2007, 06:39 AM   #208
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Default CAPS GOOD SPECS

Can somebopdy give some information about the specs of a good Cap?

thanks in advance
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Old 02-22-2007, 02:25 AM   #209
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Quote:
Originally Posted by Drcy
Can somebopdy give some information about the specs of a good Cap?

thanks in advance
Spec for ESC should be :
rated ripple should be more / higher than 2,000 mA rms
ESR / impedance should be lower than 0.05 ohms max.

That's so far I know....
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