Cap Pack - two types - one for ripple one for boost?

[RC-Dude]

Have this question that keeps coming up. Here two scenarios:

1) In order to reduce ripple give the ESC some TLC add a cap pack as close as possible to the ESC.

2) What about buffer cap packs? Like a set of 4 to 6 1500μF caps parallel somewhere between ESC and lipo. Preferably with a 8mm socket and plug that fits right inbetween ESC and lipo connection. The function would be to give that extra boost when accelerating or doing a speed run. Easier to install and also possible to move to another rig by unplugging and installing. Also for example in hot weather to reduce the stress on the ESC. It just gives that extra power and supports the battery during power surges.

The difference to 1) would be that it's not close to the ESC. Would also make it easier to place in the rig. And you don't have to open the ESC wires and solder. Is there an electrical reason that absolutely speaks against it.


Does that make sense or am I missing something?

 

[nino]

It's the same thing, but the caps farther away will see more resistance to the ESC and won't be as effective.
For using connectors, someone with more knowledge than me should do a calculation to see if the added contact resistance will negate eny beneficial effects the caps bring.

I have some experience building amplifier power supplies and the rule is to keep the caps as close as possible to the output transistors with thick wiring, and they're always bypassed with smaller electrolytics + polypropylene caps right at the PCB.

tl;dr: as close as possible to the ESC and bypass with smaller (100nf or so) film caps to reduce ESR. More cheaper smaller caps in parallel is better than big ol cans (everything else being the same).

 

[gotnitro]

Cap packs don't work for ANY extra power or boost OR speed on a speed run.. They are powered by the battery you plug in... They don't hold any more voltage (POWER) than the battery can supply lol. Your ESC already has caps on the board, no need for these unless you like RC "eye candy" to some but to me they look like RC clutter.

 

[RC-Dude]

I'm aware of cap packs not beeing able to replace good batteries, ESC and wiring. I recently popped a capacitor on a Max6. So I was wondering if an extra cap pack would have made a difference. And if a cap pack would make sense as a simple battery support especially with lots of accelerating on a parking lot with very grippy tires. After all most lipos do have unrealistic c-rates. Then on the other hand I'm not sure if the capacitor just got too hot and should have just had a stronger fan.

In EDF jets I always use them as the cables between ESC and batteries are very long. The ESC is more in the middle of the plane and gets cooled by the airstream of the intake. And inevitably the lipos are a lot further in the front to get the Center of Gravity in the right place.

 

[SrC]

2) What about buffer cap packs? Like a set of 4 to 6 1500μF caps parallel somewhere between ESC and lipo. Preferably with a 8mm socket and plug that fits right inbetween ESC and lipo connection. The function would be to give that extra boost when accelerating or doing a speed run. Easier to install and also possible to move to another rig by unplugging and installing. Also for example in hot weather to reduce the stress on the ESC. It just gives that extra power and supports the battery during power surges.

The difference to 1) would be that it's not close to the ESC. Would also make it easier to place in the rig. And you don't have to open the ESC wires and solder. Is there an electrical reason that absolutely speaks against it.


Does that make sense or am I missing something?

Aside from the wiring being all to far from the ESC's PCB , negating efficiency, there will simply be No "BOOST" of any sort. And Caps do nothing for ESC heat control in hot or cool weather. One standard quality Cap pack is all you need. And much depends on the ESC and setup you have. There should be a need to do it. Not just because. Only CC data logs can actually show Ripple. So there is no way to judge otherwise, the results of doing this. IMHO. Best to keep the wiring as Lean and mean, as best possible for basher rigs. With dedicated Speed Running, thats a whole different animal.
.

 

[LicketySplit]

simple battery support

Caps aren’t battery support. They are FET supports. Unfortunately splicing into your ESC wires is necessary otherwise you really aren’t helping much by having caps further away.

 

[LibertyMKiii]

I made a giant 21uF pack a year or two ago and if you charge up the caps and disconnect the battery they cannot power the motor alone. Their ability to provide amperage is almost nothing. Their only measurable function is to smooth out oscillations in the voltage.

 

[SrC]

Nice Cap Pack.
Are those caps Panasonic Gold's?
The Low ESR ones?
Nice!!!

 

[LibertyMKiii]

Nice Cap Pack.
Are those caps Panasonic Gold's?
The Low ESR ones?

Yes sir, I have always used those for all my cap pack builds.

My preferred way to make a pack is to set them up like below and put clear heat shrink on them.
Or use a PCB board, but this works and is simple/easy.

Since moving to the XLX2 I don't need cap packs anymore. It was mostly for MMX6s and MMX8s ESCs.

 

[Garcbomber]

After recent purchase of a MMX8s and their "less than stellar" capacitor set, please sell me on why I'll require an external cap pack for speed running.

Does anyone have a back-to-back runs with/without an additional cap pack? Looking for improvement in performance-top end MPH along with any obvious heat/failure or voltage sag "apples to apples" comparison.

Thanks

 

[SrC]

@LibertyMKiii That is quite the perfect setup there.

 

[dk10438]

I made a giant 21uF pack a year or two ago and if you charge up the caps and disconnect the battery they cannot power the motor alone. Their ability to provide amperage is almost nothing. Their only measurable function is to smooth out oscillations in the voltage.

View attachment 319928

Any thoughts on these??

 

[SrC]

After recent purchase of a MMX8s and their "less than stellar" capacitor set, please sell me on why I'll require an external cap pack for speed running.

Does anyone have a back-to-back runs with/without an additional cap pack? Looking for improvement in performance-top end MPH along with any obvious heat/failure or voltage sag "apples to apples" comparison.

Thanks

I don't think a Cap Pack will address what you stated.
And Yeah the MMx8s and XLX2 don't even need any additional Cap pack.
CC Data logs show little if any Ripple 99% of the time. You know this already.
In most cases The Lipo packs are the weak link if anything. And No Cap packs will compensate for this.

 

[MrWednesday]

It's the same thing, but the caps farther away will see more resistance to the ESC and won't be as effective.
For using connectors, someone with more knowledge than me should do a calculation to see if the added contact resistance will negate eny beneficial effects the caps bring.

I have some experience building amplifier power supplies and the rule is to keep the caps as close as possible to the output transistors with thick wiring, and they're always bypassed with smaller electrolytics + polypropylene caps right at the PCB.

tl;dr: as close as possible to the ESC and bypass with smaller (100nf or so) film caps to reduce ESR. More cheaper smaller caps in parallel is better than big ol cans (everything else being the same).

That’s the first time I’ve ever seen a tldr summary, clearly I need to spend more time on redit.

 

[LibertyMKiii]

After recent purchase of a MMX8s and their "less than stellar" capacitor set, please sell me on why I'll require an external cap pack for speed running.

Does anyone have a back-to-back runs with/without an additional cap pack? Looking for improvement in performance-top end MPH along with any obvious heat/failure or voltage sag "apples to apples" comparison.

Thanks

You can read on Castle's site that ripple voltage exceeding 10% can damage the ESC.
I personally have not seen gains in MPH, but I also was not checking for that. It was always just trying to help my purchase last longer and not get damaged.

Any thoughts on these??

I have never owned one or have any close friends who use them, so I cannot provide any sort of testimonial. From what I understand, they are top-notch in quality.
If you are looking to purchase a cap pack the flo-packs products would be one of the best products to go with.

 

[SrC]

Yeah over 10%+ ripple is what ruins the ESC. The top dog CC ESC's don't even see more than 1% if that, in many cases without any Cap Pack.
Ripple volts should always be less than than 10% of the Lipo packs mains voltage. If your ESC doesn't have any Ripple data to evaluate, a cap pack can't hurt you. Again only needed for speed running with high Amp pulls IMHO.

 

[jkflow]

It will hurt your wallet

If ripple is too high the caps will overheat and burn out, that increase chance of damaging your ESC, you got lucky.
Keep ripple below 10% and all is well. There is no magic boost in speed or anything.
In theory, if you have a large enough cap pack, you can reduce a voltage sag when accelerating but the size of that cap pack probably requires a small trailer for your RC, not practical.

 

[dk10438]

I don't think a Cap Pack will address what you stated.
And Yeah the MMx8s and XLX2 don't even need any additional Cap pack.
CC Data logs show little if any Ripple 99% of the time. You know this already.
In most cases The Lipo packs are the weak link if anything. And No Cap packs will compensate for this.

you're in the minority here.... I think it's pretty well known that the MMX8S suffers from excessive ripple (defined as greater than 10%).
you're other statement with the XLX2 having ripple under 1% is also wrong. I think most people would agree that ripple isn't an issue with the XLX2 but it's definitely over 1%

 

[SrC]

Don't take my quoted numbers literally. i never claimed to have specific CC experience. But I know how to read CC graphs.
I am in the general ball park to the OP's question.

When was the last time you saw Raz S. using a cap pack?
Not commonly used.

 

[Dan B.]

Aside from the wiring being all to far from the ESC's PCB , negating efficiency, there will simply be No "BOOST" of any sort. And Caps do nothing for ESC heat control in hot or cool weather. One standard quality Cap pack is all you need. And much depends on the ESC and setup you have. There should be a need to do it. Not just because. Only CC data logs can actually show Ripple. So there is no way to judge otherwise, the results of doing this. IMHO. Best to keep the wiring as Lean and mean, as best possible for basher rigs. With dedicated Speed Running, thats a whole different animal.
.

Right, but just because HobbyWing ESC’s don’t provide data logging doesn’t mean that ripple doesn’t exist. I installed Phil‘s 8s Ripple Killers on my last speed build. An 8s capable cap-pack on a Max 6. I have no way of quantifying its benefits, or lack of, but I’m hoping to overcome the ESC’s cut off due to amp load at WOT as it nears 100mph. From the research I’ve done, the arguments support a theoretical advantage. I don’t expect “boost” from the cap pack, or some sort of magic bullet, just the ability of the cap pack to somewhat smooth ripple enough to avoid ESC cut off under high loads.
In regard to your earlier post, the general consensus from speed runners pulling (and understanding!) Castle logs is that the MMX8S most definitely benefits from a good cap pack. Many do say that the XLX2 either doesn’t need one at all, or at least needs it to much less of a degree.
And just to be clear, I am not one of those who yet understand the nuances of reading the Castle logs or have anywhere near the experience of those whose results I’m citing.

I made a giant 21uF pack a year or two ago and if you charge up the caps and disconnect the battery they cannot power the motor alone. Their ability to provide amperage is almost nothing. Their only measurable function is to smooth out oscillations in the voltage.

View attachment 319928

Interesting. In my above referenced build, I tested the cap packs with the same method that Jason did in his FloPack video. I let them charge for awhile with electronics armed and then pulled the battery while the ESC was still powered up. Like you, I experienced nothing after disconnecting the LiPo. It would not even briefly power the servo, ESC, or fans. Are Jason’s units simply that much better, or am I missing something here? I was surprised that literally nothing happened.
And again, I’m not expecting something over the top. Just the ability for a quality cap pack to handle ripple and voltage sag to some limited extent.