I feel with you! All the waiting, no problem. But this made me freak out!
buy some 63v or 100v Caps from some nearby online electronics store & send me the bill.
I really donāt know people are getting upset here, @onloop is following his manufacturerās recommendations. Iām pretty dam sure the guy who proposed this recommendation is an electrical engineer. This modification should be trivial for you guys.
Got my VESCs yesterday and theyāve got 63v caps! First thing I checked out of curiosity after reading this, Jason apparently worked it out with the manufacturer very quickly! Or they have run out of 50v caps and now only have 63, so I think everyone should be alright.
So would it be possible to get confirmation, hopefully from @onloop. If I have 63v capacitors on Enertion VESCs (which I do), am I safe to run 12S?
Would be a nice bonus if true, as the specs on the Enertion site state 10S max, so I was aiming for 8S, but the motors can handle it, so if I can stick another 4S LiPo on there that would be great.
incorrectā¦ the impedance of a cap or inductor refers to resistance but also reactance āXā - the time-varying phase shift of the current or voltage itās resistingā¦ that doesnāt get āspentā in the form of heat.
The ESR or Resistance is the actual resistive component of the inductance (think total Z = 1/jwC + ESR) or X + ESR
The ESR being high means, when you try to pull a lot of current, V=IR will be your voltage drop from the cap internals out the wire, to your VESC. So if there was 0.1 ohm ESR and you tried to pull 10A out of a 40V cap, you would only āseeā about 40V - 0.1(10) = 39V. Imagine an instantaneous inrush of 100A and you lose 10V!
If you start combining a bunch of caps into one package or picking cheaper, larger values you typically have an increase in ESR which not only heats up your cap (shortening the life) but is less ārealā - the capacitance isnāt really at the voltage you want after it is burnt across the ESR. The cap heating effect is why your capacitor has a āripple currentā rating meaning how much watts it can passively dissipate as it is constantly burning back and forth as current moves across it. I doubt builders like Jason are measuring these values in their design. Note that for every 10 deg C you increase the temp of aluminum electrolytic caps the lifetime is cut in HALF!
Definitely study up on reactance vs impedance vs resistance as you finish your EE degree as people love to ask this sort of shit in technical interviews
Does that mean that multiple capacitor might be less preferred than a single, big capacitor because its will combine the ESR, increase the resistance between positive and negative and means an increase in voltage drop?
Sorry if its a stupid quesion.
Multiple capacitor do ācombine the ESRā as you say, but they combine in parallel meaning overall resistance goes down.
Imagine 1 guy with a pile of 100 snowballs VS 10 guys with a pile of 10 snowballs each. Which would you rather get in a snowball fight with
My bad, Iām not sure why I typed āincreasedā what I have in mind is reduced
So does that mean that bigger capacitor is better since its just a single capacitor or the ESR is relative to farad?
Sorry I have no idea about this. I only know the basics of resistors. Parallel is subtraction and series is addition
Series may be addition but parallel is hell no subtraction (If I start with 1 ohm and put two more 1 ohm in parallel do I get negative resistance? )
Bigger cap is better from an energy standpoint - And you can always pay more money to get lower ESR for any given size cap - but if you could choose 1x660uF or 2x330uF , the 2x will probably deliver it more effectively (inductance is also a factor with long package leads and high di/dt). The only reason to go single big package is cost.
Ok, my bad again. Heh. But 2x1ohm in parallel is 0.5ohm. Is that right?
I should start reading more
But I appreciate your insight
Hello guys,
Iāve read many posts about caps as my vescs are the ones with a big cap instead of 3 smaller ones.
At the moment I would like to change my caps but I am wondering what is the typical Vue for a low esr for the vesc.
0.1ohm is what we should aim for? Lower? Iām trying to figure out what values I should be looking for.