Additional Caps, Why?

[Snowride]

I just picked up an extra T180 from HK and noticed they have added 4 smaller caps to the unit. I have 2 other T180's with no additional caps. Why did they do this and would it be prudent to add more to the older units?

[Boaterguy]

the reason capacitors are there are for a cushion.
capacitors are like small batteries, they store a charge and when there is a lack of current they supply enough to keep the current even. of course a tiny little capacitor can't compensate for huge current changes.
batteries can only supply a certain amount, when current is drawn, they will drop in voltage and cause ripple current, the degree is related to the amount the packs can supply and the amount of current drawn.
the capacitors are there to compensate for the ripple current in high draw applications, the more the ripple current, the more current has to pass through the capacitor and heats it up, the more the capacitors, the less each one has to work and less each one will fail.
DO NOT put more voltage through caps than they are rated for, you can put 20 volts through a 100 volt capacitor but you can not put 20 volts (4S) through a 16 volt capacitor (common ratings) even if you do find a capacitor rated for the exact voltage, it is better and highly recommended (unless you like burnt equipment) to over rate your caps, just like everything else.

[Snowride]

Thanks for the great explanation. I see they sell caps here at OSE. Where can I get the little boards to solder them too?

[siberianhusky]

Ripple current has nothing to do with the battery not being able to supply current.
Ripple current is the difference between the voltage during the on PWM cycle and the off pwm cycle.
The caps do not make up for ripple current they smooth the ripple current, so you end up with cleaner DC, smaller spikes.
About the only right part above is the part on choosing you caps value.
Works about the same as using caps to filter DC current after AC has been rectified.
If your batteries can't supply the load then you are experiencing sag and a cap will not make up for that.
Confirmation of this came from Patrick at Castle, so not just something I made up!
There is a ton of info out there about ripple and switching circuits.
You can get small perf board from Radio Shack (well used to be able to) might still have some on the shelf from old stock.

[Snowride]

Thanks for clearing that up.

I see they added 4x 370uf 35v capacitors to the T180. Soldering them to the board and then soldering the leads to where the battery leads are soldered to the board. Being 4x 370 = 1480. Can I solder a single large Cap to the + & - terminals to achieve the same thing or are the several caps better. Was thinking of using one of these soldered directly to the batter wire terminals on the board for grater capacity. http://www.ebay.com/itm/25-Tech-Cap-...#ht_752wt_1180

[siberianhusky]

http://www.youtube.com/watch?v=vqapTwk1Rpw

cap vs. no cap tests on a scope. Quite the difference!
Either will work, Ideally a large cap and a couple of smaller ones would do the best job of smoothing ripple.
The big cap will handle most of the 1st order filtering then the smaller caps do the higher order filtering.

[Snowride]

Really appreciate the assistance here. The T180 comes with 3x 1000uf 35v caps installed already so will adding the single 4700uf 35v as shown in the link be at least equivalent,equal or better than the version 2 of the T180 which has an additional bank of 4x 370uf 35v units connected?

[Boaterguy]

it may not be exactly equivalent but it should be sufficient if you keep your setup reasonable.
anything is better than nothing.

[Snowride]

it may not be exactly equivalent but it should be sufficient if you keep your setup reasonable.
anything is better than nothing.

My thinking was 4x 370uf = 1480uf and therefor 1x 4700uf was far superior when it come to total storage capacity. Am I thinking wrong here?

[Boaterguy]

from post 6: "The big cap will handle most of the 1st order filtering then the smaller caps do the higher order filtering."
therefore the esc with the big cap will have no large range ripple current but more fine range ripple current.
vice versa for the esc with littler caps.
this is all assuming you push your packs and ESC.

[siberianhusky]

Boaterguy give it up! Large range and fine range? What the hell is that? If you don't know something don't make up some BS to try to cover your ignorance!
That was also assuming you were using both small and big caps, not one or the other!
You will be fine with the one big one, I've done it both ways and really can't tell a difference. In running that is, if you put it on a scope you would see some difference.
If you were using them in a twin setup I'd match them but in a single you'll be OK.

[Snowride]

Thanks SH, will go with the addition of 1 larger cap. This requires no board and a simple solder on each side to accommodate. I also have plenty of room for this so this will work very well.

[siberianhusky]

I do tube amp repair as another hobby, to be honest I just root through my box of caps and use whatever I come up for escs with as long as they are low resistance. Sometimes it's a single large one sometimes a pair of medium, lol or a few of different values! As long as they are capable of handling the voltage you're good to go just about any way.

[runzwithsizorz]

By lurking, corroborating, cross referencing, and occasionally asking the dumb question, I am slowly getting schooled on this hobby. Your input, siberianhusky, has not gone unnoticed, and is appreciated.
However, I would kindly ask you to be a bit more tolerant,(i.e. ignore), some of us unwashed amongst the masses.

[LarrysDrifter]

Its not that he should ignore the unwashed. The problem lies with the unwashed giving out misleading information with almost every post they make. Its not you Runzwithsizorz, its type happy Boaterguy that misleads the masses constantly.