Power Caps

Old 03-13-2003, 04:27 PM
  #16  
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Originally posted by adz
BUT>Think of a REAL CAR with a great big whopping sound system restricted to a 6 to 9 plate lead acid battery, every time the amplifier or amplifiers require a huge lump of current draw (eg. that pain in the ass doof doof sound you hear from miles away!)
the battery suffers to supply the correct amount of current causing the driver ic's in the amp to run uneffeciantly, over heat, shutdown or in some cases 'crap out all together!'
Dunno how much into ICE you are Adz, but there's a lot worse consequences than that.

An underpowered amp (as in "too little voltage in") will pump out jagged signal spikes... this is heard as Distortion & clipping. Distortion is VERY BAD for your speakers!!! Doesn't matter that power rating they are, even if they're in excess of what the amp can pump, distortion will damage your voicecoil and cones.

Imho, most of the "DOOF DOOF" cars have owners with obviously crappy hearing and shot speakers. Their woofers work though!!

Putting a large capacitor cures most of these underruns... however one large cap eg 1F or 2F (yeah, one Farad) might not have a fast enough response time.

Your sound would become "duOOF duOOF"...

To cure this we use multiples of smaller caps in parallel... which have a faster response each. Make an array... and they don't even have to be all same size. In fact, different sizes in parallel work better too.

You now have "dUf dUf"... yeah, can't help you on your choice of music there, but you'll notice its a lot 'tighter' and 'better controlled'. It does not necessarily have to be any louder, but you'll start noticing some extra detail in your music. (assuming ears aren't shot already)

There is no such thing as "too many caps"... I know of systems that can continue running for 5-10s purely on their caps after their main power source has been disconnected. These give good sound, and the last thing you'll think to play on this is a recurring drum beat.
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Old 03-13-2003, 04:31 PM
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Originally posted by nerdling
Thanks for the info guys. I know Caps won't increase top speed, I was after more run time, sounds like two 4700uf caps in parralel accross the batterie side of my esc will do much the same thing as a 22000uf wired up the same.
Think you got your maths crosswired somehow...

Two 4700 caps in parallel = 4700+4700 = 9400uF.

Did you really mean 22,000? Wow... this'll be size of a D-cell!!
Use 4 or 5 4700s in parallel for approx the same.
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Old 03-13-2003, 04:36 PM
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Oh, btw I don't think any amt of caps will give you "more runtime" either; it won't be too noticeable. To run longer:-

1) gear down

2) use less-hot motors
2a) motor in good condition?

3) got good batteries?
3a) good charger?

4) max your ESC drive freq... higher = better

5) change your driving style, don't mash the gas.

...or

6) buy a nitro car
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Old 03-13-2003, 04:46 PM
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actually a low ESC drive freq...yeilds more runtime but the speedo does not feel as smooth. this has been discussed in depth on threads elsewhere on rctech.
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Old 03-13-2003, 08:38 PM
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I have had some experience with caps (mounted across the batt)
I tried small values and large (3x8800 high rate discharge caps) and noticed no real difference in punch or run time. The thing I did notice was that there was a small difference in the spooling speed of the motor. with large caps I was not able to "gear up" the motor as far because it would take to long to wind out....

Anyway I only run stock anyway so I don't know much about the effect on mods.

I am curious as to how much cooler a motor is supposed to run using caps? Does anyone have any exp with this?
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Old 03-13-2003, 08:45 PM
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Originally posted by Dragonfire
I am curious as to how much cooler a motor is supposed to run using caps? Does anyone have any exp with this?
According to the Novak manuals, I think its the ESC that runs cooler with caps, not the motor.

You can download Novak manuals from their website: www.teamnovak.com
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Old 03-13-2003, 08:54 PM
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WC, cool, where are the caps in a car stereo installed?

tried most you of what you said, higher wind motors, good charger/battires, geared down.

Not tried changing frequency - white man magic, but will give it a go.

Trying to smooth driving style, I come from stock land so normally it's mash the throttle and hold on.

Don't like Gas cars.

Oh yeah, my maths is fine, the example that started me thinking about this was a mod car with a 22000uf car installed accross the motor side of the ESC. I was drawing on what BK said, that he uses two 4700uf caps in paralell.
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Old 03-13-2003, 09:58 PM
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Originally posted by WC
Dunno how much into ICE you are Adz, but there's a lot worse consequences than that.

An underpowered amp (as in "too little voltage in") will pump out jagged signal spikes... this is heard as Distortion & clipping. Distortion is VERY BAD for your speakers!!! Doesn't matter that power rating they are, even if they're in excess of what the amp can pump, distortion will damage your voicecoil and cones.

Imho, most of the "DOOF DOOF" cars have owners with obviously crappy hearing and shot speakers. Their woofers work though!!

Putting a large capacitor cures most of these underruns... however one large cap eg 1F or 2F (yeah, one Farad) might not have a fast enough response time.

Your sound would become "duOOF duOOF"...

To cure this we use multiples of smaller caps in parallel... which have a faster response each. Make an array... and they don't even have to be all same size. In fact, different sizes in parallel work better too.

You now have "dUf dUf"... yeah, can't help you on your choice of music there, but you'll notice its a lot 'tighter' and 'better controlled'. It does not necessarily have to be any louder, but you'll start noticing some extra detail in your music. (assuming ears aren't shot already)

There is no such thing as "too many caps"... I know of systems that can continue running for 5-10s purely on their caps after their main power source has been disconnected. These give good sound, and the last thing you'll think to play on this is a recurring drum beat.
IMHO most DOOF DOOF cars are crap full stop... never mind the listener... and this comes from aguy who seriously played around in SPL competitions for a couple of years

where are you from WC? your use of the ICE term leads me to think maybe the U.K... the only place where that term has ever been widely used

in My car audio experience 1 farad caps are pretty much "normal" practice now and considered the minimum for a serious system, with most manufacturers such as Stinger etc offering 1.5 farad as well

I've never had ANY experience with lag in response time with large caps... all quality caps start discharging within 1000ths of a second after the power supply is removed... otherwise their purpose in a car audio install is pointless... caps are meant to provide the instant power required by the amplifier to reproduce transient peaks in the music (usually bass related but not always) so unless their response was instant they would be a pointless addition
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Old 03-13-2003, 11:24 PM
  #24  
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i actaully have a cap the size of a D cell
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Old 03-13-2003, 11:25 PM
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and its only 330 uf

but does 400 V
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Old 03-14-2003, 11:51 PM
  #26  
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i soldered 2 more caps on my car today across that battery,
i found a minor difference

so i had 4 caps
two 2200 uf
and two 3300uf

whats the general voltage rating of a cap for an rc car?
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Old 03-14-2003, 11:52 PM
  #27  
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my motor died today aswell

it was 8 years old and was ran very hard with absolutly no maintance, only now it has started to drop off performance wise....

pretty good for a stocker with no maintance
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Old 03-15-2003, 03:51 AM
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Originally posted by sausage_link
whats the general voltage rating of a cap for an rc car?
10 volts should see you clear... most small caps commonly available are rated between 10 and 16
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Old 03-15-2003, 04:49 AM
  #29  
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Dunno how much into ICE you are Adz, but there's a lot worse consequences than that.
WTF is ICE
OR have u been watching to many re-runs of cops.
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Old 03-15-2003, 01:49 PM
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Originally posted by adz
WTF is ICE
OR have u been watching to many re-runs of cops.
ICE = In Car Entertainment... or in other words car audio or car stereos...

it was created by some british mags to describe car audio when tv screens, game consoles, and dvd began being included in large custom fittings
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