Trying to understand cap packs and why they are necessary; Trying to decide if I "need" a cap pack

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dk10438

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Arrma RC's
  1. Limitless
setup
Limitless
MMX8S
CC1650-1717
3sSx2 CNHL Racing 6200Mah 90c
34T/39T
I was looking a my logs and saw that my ripple was 2.7-2.8v which puts me at 11%.

My wiring is a bit messy, ie ESC to QS8 to Qs8 y harness to QS8 battery connectors so I suppose I could ditch the harness and solder QS8 connectors to the ESC wires like most setups.

I understand that cap packs are recommended when ripple exceeds 10%. My question is what happens if I ignore the recommendation for a cap pack?

Premature ESC failure and slow death? ESC catching fire? Sudden ESC failure resulting in a potential crash and total loss?
 
Simply put they hold energy for when the ECS needs it.
Just like in a car audio system the cap holds energy to help with the extra "oomf" when the bass hits.
Doesn't help with more speed but help with a solid speed.

Sorry that made sense in my mind. 🤪
 
Simply put they hold energy for when the ECS needs it.
Just like in a car audio system the cap holds energy to help with the extra "oomf" when the bass hits.
Doesn't help with more speed but help with a solid speed.

Sorry that made sense in my mind. 🤪
you seem to be a seasoned contributor but that's not quite what I read....
Capacitors hold and store energy, I agree with that. However, my understanding is that under high load the ESC is "turning on and off" very rapidly and this switching can be damaging to the ESC. Thus, cap packs helps to smooth this out. Since this is occurring almost instantaneously, no/minimal effects are seen in voltage sag or performance. The addition of cap packs is to lessen the strain on the ESC? High voltage ripple results in premature ESC failure? That's what I thought I read anyway...
 
you seem to be a seasoned contributor but that's not quite what I read....
Capacitors hold and store energy, I agree with that. However, my understanding is that under high load the ESC is "turning on and off" very rapidly and this switching can be damaging to the ESC. Thus, cap packs helps to smooth this out. Since this is occurring almost instantaneously, no/minimal effects are seen in voltage sag or performance. The addition of cap packs is to lessen the strain on the ESC? High voltage ripple results in premature ESC failure? That's what I thought I read anyway...
Which pretty much what I stated in a more simple way.
It smooths out or "gives the ESC the oompf it needs when it needs it" so as to keep it level or smooth.
Though ripple can have different factors also. Best bet is to make sure it's not other factors before adding a cap. imo
Which pretty much what I stated in a more simple way.
It smooths out or "gives the ESC the oompf it needs when it needs it" so as to keep it level or smooth.
Though ripple can have different factors also. Best bet is to make sure it's not other factors before adding a cap. imo
oh btw, not seasoned nearly as much as others here. I'm still learning like most.:)
 
Which pretty much what I stated in a more simple way.
It smooths out or "gives the ESC the oompf it needs when it needs it" so as to keep it level or smooth.
Though ripple can have different factors also. Best bet is to make sure it's not other factors before adding a cap. imo

oh btw, not seasoned nearly as much as others here. I'm still learning like most.:)
not to be argumentative but more "oomph" implies more performance.
What I'm reading is ripple higher than 10% can cause ESC damage and what I'm trying to understand is how that damage occurs
 
not to be argumentative but more "oomph" implies more performance.
What I'm reading is ripple higher than 10% can cause ESC damage and what I'm trying to understand is how that damage occurs
Sorry maybe a bad choice of words but I meant just extra energy that the ESC is scraping for.
It helps it run as should...not run better.



Maybe a more technical explanation will help.
I'm sure more will chime in soon.
Hope you figure it out.(y):)
 
What can happen? Your ESC might get damaged.
No, they do not provide any power to the ESC, big misconception. They filter the voltage, is a better acronym.

ESC is always switching power on and off to the motor (winding), when it turns off you get some back voltage from the motor.
This will cause voltage spikes and drops (or peak and valleys) at the input side as well as throughout the system. This voltage is higher than the lipo voltage and will cause damage to ESC components.
The cap pack eliminates those spikes or at least tries based on the capacity. It almost eliminates these spikes.
The higher the current in the system, the higher that back voltage and the bigger the capacitance needed to compensate.

Recommended if you go regularly above 10%.
Keep in mid that the ESC logger might not catch the peaks as it's logging speed in 1/10 of a second while these ripples are easily 10000x faster.

You can also google for this question, and you will a detailed analysis. Hard to fit this into a few words.

Cap packs need to be wired as close as possible to the ESC input terminals to be useful.
 
Might get damaged doesn’t sound very definitive to me….
But going back to my original question, how does the damage manifest itself?
Capacitor catching on fire?
Capacitor exploding?
Slowly degraded performance?
Not turning on one day?
Shutting down during a high speed run?

Any of the above???
 
Might get damaged doesn’t sound very definitive to me….
But going back to my original question, how does the damage manifest itself?
Capacitor catching on fire?
Capacitor exploding?
Slowly degraded performance?
Not turning on one day?
Shutting down during a high speed run?

Any of the above???
Bad or excessive ripple can and in extreme cases will cause the electrolyte in the capacitors to vaporize and blow off the vents on the top which could potentially cause a short circuit when they come apart, if for some reason the esc doesn't go into current over load before that lol its there from the factory for a reason on most escs. The esc will get really hot with too much ripple and will easily be noticed if the esc stutters or the power shuts off under heavy load. Ive had some hobbywing escs shut down completely because they use the push button to turn the power on and off instead of a physical sliding switch. Some of the escs with the sliding switch just reboot, count the lipo cells and keep going.

So ya too much ripple may cause catastrophic falures such as capacitors exploding, esc fires, and other strange glitchy behavior. More than likely that it will go out with a bang or just die while driving

The max 8 and blx 185 escs don't take oversized motors well, i know because i cheaped out and tried it. I figured adding capacitors would fix it and it helped for a while. it wasnt very long till mine shot flames out of the capacitors and all the mosfets turned into a smoke bomb…

If you arent sure if you should put capacitors on it just do it to be safe. Take the amount you think you need and add a few more. As far as i know theres no negatives to extra capacitors accept for looks and the big spark when you plug in big batteries.
 
From the CC site.
Capacitor: A capacitor is a passive electronic component that stores energy temporarily. It protects the rest of the components on an ESC by smoothing out the ripple on the input side. Ripple is generated due to the rapid operation of components on the ESC.

I see a new reply above that answers your question as to what can happen.


"Might get damaged" is pretty definitive if you ask me. These things cost too much to take risks with imo.
 
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Wire length between the battery and esc and inductance is very important i found that out the hard way in a few rc planes. Always causes the esc to “lose track” of the motor and ends up energizing the coils in the motor all wrong then cutting out when applying throttle too quickly. definitely not good because it always happens in a “oh crap!” Panic moment. Timing probably had something to do with it too but im to lazy to program them.
 
Might get damaged =
Voltage spikes exceed the rated voltage of components. Capacitors will degrade, loose capacitance and exacerbate the problem. Eventually the spikes will exceed the rated voltage of the 'FET' that do the switching.
It will be a silent death, parts simply stop to operate.

This can be precisely pinpointed with a capable oscilloscope or data logger that operates at 10x the switching frequency of the ESC. The problem is strapping on an instrument of that size, by all means, all it will tell you at what time your ESC died and how much of an exact ripple voltage spike it took on your ESC. :rolleyes:
 
Might get damaged =
Voltage spikes exceed the rated voltage of components. Capacitors will degrade, loose capacitance and exacerbate the problem. Eventually the spikes will exceed the rated voltage of the 'FET' that do the switching.
It will be a silent death, parts simply stop to operate.

This can be precisely pinpointed with a capable oscilloscope or data logger that operates at 10x the switching frequency of the ESC. The problem is strapping on an instrument of that size, by all means, all it will tell you at what time your ESC died and how much of an exact ripple voltage spike it took on your ESC. :rolleyes:
My experience has been far less "silent", in which the voltage spike takes out the FET and shorts out. 🔥
 
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