Capacitors, When to and when not to use them??

[FliteRisk]

I am working on my third build and the first quad I built is having no issues and it does not have a capacitor. The second build is having issues with losing control after extreme inputs for full throttle, flip, or roll. Now I am building the third one and I am about to solder the battery lead onto the 4-in-1. When do you feel the need to use a capacitor? What rating do you use for 4s batteries?

 

[RENOV8R]

There is no negative effect to having a cap so I always add one when doing a build. But this is more for having clean video. If you're having control issues because of noise, that's pretty extreme and I'd look at mechanical resonance issues or incorrect filtering. As for ratings, I'm assuming you're asking about C rating? Most use 100C, 90C would be the lowest I'd go

 

[wafflejock]

The capacitor just needs high enough voltage rating for the input voltage if using 4S it's 16.8V so getting 24V or 50V capable capacitors works fine for farads think something like 400uF per ESC is good but power filtering does depend on the type of capacitor and other things so only add them myself if video is getting noisy power (typically looks like lines in video feed that get worse with throttle). The quad freaking out is likely in need of soft mount of the flight controller basically passive physical filtering or as mentioned adjusting the software filters to remove motor vibration from the equation so the gyro is giving the actual motion of the thing instead of vibrations from the frame, long story short probably just need to improve that signal to noise. If you messed with the PIDs would put them back to defaults on that one and see if maybe exaggerated I term or something else is causing a runaway/flip out.

If using electrolytic capacitors just make sure white stripe side is hooked to GND or negative other side is positive or can blow the cap.