nerdling

iTrader: (8)

I've been seeing a lot of Mod buys using big power caps in their Cars. Along the lines on 22000uf.

Is anyone out there doing this?
If you are, what Spec are you using?
When did you get it?

black-knight

I run 1 or 2 4700mF caps, the caps are purley for dissipating noise and smoothing out voltage spikes. Caps also reduce the operating temperature by up to 20 degrees. Most speedos melt if caps are not used or if the cap fails during a race.

Coxy

Yes very true. I have had my old tech system in my work research area. I could not believe the spikes shown and then smoothed out when put on test equipment. But as for more power, none to get excited about.

Coxy.

Dragonfire

iTrader: (1)

where do run your caps? across the batt or across the motor?

AC

battery inputs on the speedo.

nerdling

iTrader: (8)

Hmmm intersting, the ones I've seen are accross the motor.

Would not a cap help when you snap open the throtle? The Cap would discharge straight into the motor taking the amp draw that would otherwise hit the batters?

Result more punch - Cap's discharge much faster then battries.

This is what I assumed they do.

WC

iTrader: (28)

Power Caps are always across the battery. Putting them on your motor leads do nothing; power still has to go through your ESC first, so your motor isn't getting anything 'extra'. Also think what happens when you hit the brakes... charged cap + brake FET?


Big caps have slower "discharge" rates than smaller caps. If you really think those extra electrons make a difference then you should make up an array of smaller caps instead eg multiple 1000ufs in parallel.

Varying size of cap may change the "feel" depending who you ask, but this is quite subjective. Difference is about the same as changing the drive frequency of ESC... but end result is it ain't gonna double your topspeed.

ShadowAu

iTrader: (7)

Power caps help smooth out power supply.... and to also help the battery supply instant voltage under high load situations, eg aceleration from a standing start... caps can discharge voltage at a MUCH quicker rate than a battery

a cap of about 2200-4700 uF would be able to supply only a very short burst of voltage, probably less than 0.1 sec

larger caps have a larger storage capacity, not a slower discharge rate as stated in another post.... a larger cap will discharge for longer because it has a higher storage capacity

one large cap or a series of smaller ones make no difference to the end result

the cap will also make NO difference to braking because of where it is on the voltage input side of the speedy

caps across the motor are to help smooth out interference from the arcing of the brushes... usually they are not higher than 10uf

sausage_link

yes thats right
the cap accross the battery allows the motor to draw more power for better acceleration as well, the ones on the motor are to stop glitching as well

sausage_link

the caps across the motor are usualy rf capacitors not power caps

adz

True but for that split the cap would just be able to switch on the
transistors or FETS and be barley noticeable.

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!'

BUT by placing a massive power capacitor
parrallel across the +tve & -tve terminals of the battery, smooths and provides a more efficiant supply current and voltage(only for short bursts) hopefully correcting any supply problems alltogether.
Its a similar principle in rc.
Hope it made sense.

tabmow69

I think, Adz is referring to me or Ari, inbound to race meet. LOL.

Did you copy that explanation directly from me when I had to explain it to you ages ago? It sounds awfully familiar.

The bottom line is its for eficeincy and rf suppression.

Coxy, what do you do for work, or study?

adz

I think ur thinking of the cap across the receiver thing.
But if not i'll give u the credit anyway.
But i do remember some stuff from when i did my electronics trade.

ShadowAu

iTrader: (7)

I've been working in car audio for 9 years I was just trying to keep it simple and general....

power caps can be used across the positive and negative of the motor... as long as the value is kept small it will do the job better than ceramic caps

nerdling

iTrader: (8)

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.