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Old 03-17-2004, 09:18 PM   #1
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Default Power Capacitor to gain acceleration

Check this out!!
I just got this power capacitor. 10,000uF!!!
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3190750340

I tracked down the specs for this capacitor:
http://www.luxon.com.tw/Products/twspec.htm
The ESR (Equivalent Series Resistance) is 0.053
That seems pretty low to allow it to work fast.

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

I have never seen a 10,000uF capacitor so small. I used to have a 1000uF capacitor, but a bigger capacitor makes a difference. I run an HPI micro (18th scale), so I can't go to a bigger capacitance. This guy has a 68,000uF capacitor that is a good size for a 10th scale car, and I told my frind to order one.
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3182761038

Last edited by BigBear; 05-03-2004 at 03:02 PM.
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Old 03-18-2004, 02:15 AM   #2
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It's not just the size and capacity that matters. The capacitor has to have low ESR (Equelant Series Resistance). If the ESR is high the capacitor will work "slower" even it the capacity is high so "apparent" capacity (what the circuit sees) is less. Also capacitor with high ESR heats up.

There is nice article on capacitors on www.illcap.com

Last edited by andsetinn; 03-18-2004 at 05:25 AM.
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Old 03-18-2004, 07:42 AM   #3
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I got the same style capacitor from mouser electronics for $1.40 with pretty cheap shipping ( about 5 bucks for priority, would have been a lot less but I needed it fast ).

The cap works really well.
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Old 03-18-2004, 09:34 AM   #4
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Default Power Capacitor to gain acceleration

Guys;

You want to use an 'Electrolytic Power Capacitor'. These charge/discharge rapidly enough to work properly.

10V, 4700uf is the size you need. They are less than $5 at an Electronics Store.
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Old 03-18-2004, 01:02 PM   #5
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4700uF:
$3 each
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3182169527
I got the 10000uF.
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Old 03-19-2004, 11:23 AM   #6
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How do I you install this? Does it go on the battery or motor wires?
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Old 03-19-2004, 11:37 AM   #7
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Quote:
Originally posted by BigBear
4700uF:
$3 each
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3182169527
I got the 10000uF.
I got 10 of these for 5 bucks. I still have 8 of them.
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Old 03-20-2004, 05:55 AM   #8
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Just a word of warning.... So called "power caps" tend to have a big impact on a cars top end acceleration, but little affect on the bottom end. If you want to use a "power cap", use a smaller one to help reduce radio noise in your system. I have tested small to large caps all high discharge rate caps. Punch dosen't feel any different but the bigger the cap, the longer it took to reach top speed.
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Old 03-20-2004, 06:38 AM   #9
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I'm not going to get in a big debate, but some of the people on here need to go read up on capacitors, and not on another r/c site, but something a little more scientific. I'm afraid some people might read some of this stuff and misunderstand how a capacitor actually works.
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Old 03-20-2004, 11:15 AM   #10
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Default Power Capacitor to gain acceleration

Guys;

There is NO doubt in my mind that installing a Power Cap helps punch in a "Stock" Motor. If you can feel the difference in minor suspension changes, will WILL notice the difference using a Cap.

Mind that you want to use 10V Capacitors as they will charge/discharge faster than one with a higher voltage rating. This is also noticable.
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Old 03-20-2004, 01:34 PM   #11
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I have a 22.000 uf capacitor that i've tested on my Quantum 2.. The only difference i noticed in my SD was the weight of it that made it tweaked.. 27 grams was the weight of it, ran faster without it
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Old 03-20-2004, 02:08 PM   #12
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Sometime ago I have made the following test:

".....
Well I have done the following test (that contraries my belief)!!
OK, before throughing everything against my test, I think it could put some light on that matter.
I have put a 12x1 Core stopped and then running at 3V, 5V and 7V with my GFX. I have measure the rpm with a GlooBee digital gauge. Attached to the mtotor was a small propeller to absorb energy. Then a charged different caps, all of them 16V, 105C, ranging from 1000uF to 10000uF. Then I disccharged the caps on motor and see any differences on rpm.
Results:
. with motor stopped - nothing happened but sparks on contact
. with the different voltages applied to the motor the difference was so small that the reader doesn't measure it.

Conclusion - after that test I believe that the power cap is most used to protect the ESC rather to add any punch.
......"

Now I don't use power cap, and my times are the same or better !!
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Old 03-20-2004, 06:02 PM   #13
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Seems some ppl are seeing the light... If anyone here has seen a dyno readout they will know that an average stocker pulls of 70amps under full throttle at low speeds.. now try disconnecting you batts with the speedie still turn on... the LED will stay on for about 1 sec. If you cap can't power a 0.01amp LED for anything less than a couple of days, then it won't provide the motor with anything that it can use.

They do help to supress radio noise tho so get a little one for that purpose only.
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Old 03-20-2004, 10:59 PM   #14
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exactly... the capacitors are reducing glitching, protecting the ESC, and that's about all. most capacitors unload in the matter of hundredths of a second or less.
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Old 03-21-2004, 06:00 AM   #15
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Check this out:

Testing - Do Power Caps Make a Difference
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