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Old 12-01-2004, 10:17 PM   #136
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Quote:
Originally posted by asw7576
Oops..... so sorry guys..... bad information. I check again, it was Rubycon 16V 2200uF

The capacitor was rather hot ( almost as hot as my battery ) because I wasn't using any schottky diode yet. Interestingly, the cap and esc were so much cooler after I installed big azz schottky diode

BTW, the 6.3V 3300uF cap is installed in my other car, and truly I don't experience any different with 16V 2200uF cap. It doesn't pop or leak.
Listen to tel, running a 6.3V cap is BAD!!!
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Old 12-03-2004, 01:32 AM   #137
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What do power capacitors do anyway?
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Old 12-03-2004, 01:35 AM   #138
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Quote:
Originally posted by Team Duratrax
What do power capacitors do anyway?
They make your car look trick.

You could read thru this whole thread though
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Old 12-03-2004, 01:46 AM   #139
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lol i think ill pass
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Old 01-14-2005, 02:39 PM   #140
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Quote:
Originally posted by asw7576
I don't experience any different with 16V 2200uF cap. It doesn't pop or leak.
2200uF is too small. I notice a slight difference with a 4700uF.
You need at least 10,000uF to "experience" the difference.
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Old 04-13-2005, 10:19 AM   #141
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Quote:
Originally posted by Entropy
They make your car look trick.

LOL, ....is that why I saw 10 caps on your car the last race ?

Later !
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Old 05-06-2005, 06:17 PM   #142
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Actually I just use one 10000uF cap []
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Old 05-19-2005, 06:52 PM   #143
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Ghostfit,
What are Centerline Batteries?
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Old 05-20-2005, 02:38 AM   #144
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Hey guys,

the capacitor comes into play only during switching, that is during partial throttle. Once your at full throttle it makes almost no difference whether you've got one or not! So for all you stock guys who use a lot of full throttle I doubt it would make much difference, but for mod guys who use more partial throttle it should make a difference.

If you use very large value capacitance it means that the voltage will drop less during turn-on time in partial throttle (thus giving more voltage for the motor and more punch), but during turn-off time it will also take longer for capacitor to charge up and thus the battery vcoltage will also rise back up slower.

Small capacitor -> during on-time voltage will drop more, but will also charge up quicker.

Large capacitor -> during on-time voltage will drop less, but it takes longer to charge it back up again, so the battery voltage might be kept lower because of this.

It's good to use a capacitor but don't over do it by using too large value capacitance.

Just keep these things in mind when choosing your capacitors.

Cheers.
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Old 05-20-2005, 09:33 AM   #145
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a bit out of topic here but since we have so many experts here...can anyone tell me if 40V3A schotty diode works on 8/9T motors?
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Old 06-12-2005, 09:14 PM   #146
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Quote:
Originally Posted by AI2
Hey guys,

Once your at full throttle it makes almost no difference whether you've got one or not! So for all you stock guys who use a lot of full throttle I doubt it would make much difference, but for mod guys who use more partial throttle it should make a difference.

Cheers.
Using a capacitor on a track with lots of turns which require frequent acceleration and deceleration is when a capacitor will help the most.
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Old 06-13-2005, 11:39 AM   #147
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Bumped into this thread and became curious,

So from what I have read, higher ESR=slower charge/discharge rate?
Lower ESR comes from more capacitors in parallel?
Therefore 2x1000uF capacitors in parallel are BETTER (will charge and discharge faster) than 1x2000uF?

If they are all true, I was wondering does the ESR, factor in the fact that there will be more solder+wire due to additional capacitors which will increase its resistance? Or is this resistance negligible?? (pardon crappy spelling) and therefore it doesn't matter if we have a few more capacitors onboard?
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Old 06-13-2005, 01:37 PM   #148
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rcnewb2004

ESR is dependant on both capacitance and voltage rating, the higher the capacitance and the voltage ratings are, the lower the ESR is.
On the table that is written on my ESR meter, a 470 uf, 10 volt capacitors ESR is listed as having double the ESR of 1000 uf 10 volt capacitor.
A 470 uf 25 volt capacitor has the same ESR as the 1000 uf 10 volts capacitor in the previous example.
That gives the conclusion that you get roughly the same ESR for given capacitance at the same voltage, no matter how many capacitors you've got.
Higher voltage rating and capacitance lower ESR and make the capacitor physically larger.

ESR will increase as capacitor gets older, if it's working in a hot enviroment the ESR will increase faster. Resistance in wires doesn't really matter, most of the time the capacitor isn't doing anything much.

About using 6.3 volt capacitors.
6.3 volts is the maximun voltage the manufacturer says the capacitor is supposed to be able to tolerate without being damaged.
When the capacitor manufacturer starts his machine to manufacture capacitors, he calculates all parameters, he specifies all materials, so that the worst capacitor in the batch he's making will tolerate at least 6.3 volts.
Therefore most of the capacitors in the batch he's making will work fine with 7.2 volts. Lot of the capacitors will work fine with 10 volts. But some will only barely work with 6.3 volts.
Some manufacturers make better capacitors than others, Japanese capacitors are typically the best you can get, lowest ESR for given capacitance and voltage rating. They also last longer.
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Old 06-14-2005, 12:31 AM   #149
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Quote:
Originally Posted by Dragonfire
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.
Ssst ! ( it's our secret ! ) J/K

Anyway.... I removed mine. Feel indifference.
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Old 06-14-2005, 02:45 AM   #150
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andsetinn:

Ok, see where I go wrong with this. Because your conclusion does not make sense to me.

I am a pre-service high school teacher so I will look at this like a highschool experiment.

There are 3 capacitors, I name them A,B,C.

Capacitor A has 1000uf capacity, 10 volts rating.
Capacitor B has 470uf capacity, 10 volts rating.
Capacitor C has 470uf capacity, 25 volts rating.

My controls are:
- 1000uf, 10 V for capacitor A
- 470uf for capacitor B and capacitor C

So the objective of this experiment is:

To test how different voltage ratings on capacitors affect ESR.

This done by first comparing the ESR of:
#1. capacitor A with capacitor B
#2. capacitor A with capacitor C

Results:
Your wrote:
"On the table that is written on my ESR meter, a 470 uf, 10 volt capacitors ESR is listed as having double the ESR of 1000 uf 10 volt capacitor.
A 470 uf 25 volt capacitor has the same ESR as the 1000 uf 10 volts capacitor in the previous example."

I will translate that into:
Case #1: (Same voltage, Different capacitance)
470uf, 10 V capacitor has DOUBLE the ESR of 1000 uf 10 V capacitor.

Case #2: (Same ESR, Different voltage and capacitance)
470uf, 25V capacitor has the SAME ESR as 1000 uf 10 V capacitor.

Therefore:
Capacitor A has 2x the ESR of Capacitor B.
Capacitor A has the same ESR as of Capacitor C.

Am I correct?

Capacitor C has higher voltage ratings than Capacitor B.

Assuming that voltage and capacitance are the only two parameters affecting ESR, the conclusion I can draw from your ESR table is:

Lower voltage rating = Lower ESR.

(Which should be true. Can someone please comment to see if my interpretation is correct?)

You said that:
"That gives the conclusion that you get roughly the same ESR for given capacitance at the same voltage, no matter how many capacitors you've got."

I cannot see how you can draw your conclusions from your ESR table. Enlighten me please.


For everyone else who still have the paitence to read:
My question is simple, will additional resistance (due to wires, and solder joints) change the ESR value of a capacitor?

My next question is:
Which setup has more ESR?

setup#1 1x 1000uf,10V capacitor.

setup#2 10x 100uf, 10V capacitors in parallel.

Please give explaination!

Additional questions for the hardcore tekies out there:
How is ESR different from resistance?
Where does ESR come from?
What is factors affect ESR?

Thankyou all for taking the time to enlighten a lost newb in the rc world.
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