84jeepj10

I have been reading about installing a capacitor parallel to the power lines going to an ESC and how they affect acceleration, heat buildup and lifespan of ESC. I understand the concept but do they actually work? I have a Pro-Pulse I am considering testing it on before I get hands on my 1/8e. I understand that if I place a >=7.2VDC 3000+uF capacitor in parallel to the power lines on on my ESC that it will smooth out the current spikes and allow short but very fast bursts of current draw (when charged) so my acceleration will be faster and my ESC will heat up less as well as last longer because of less "ripple" in the current. Is this correct?

dirtybird

My Feedback: (5)

I woul expect the designer of the ESC will chose enough capacity and adding more would not help much unless you have more than 12" power leads

84jeepj10

I've been a tech on too many systems to think that the engineers think of everything. Want to know if anyone has any real experience doing this.

JoeAirPort

My Feedback: (41)

So your logic is that you know more than engineers that design this stuff, and people in this forum know more than both of you. Hmmm. That's interesting. Let me know how that works for you.

dirtybird

My Feedback: (5)

what makes you think an engineer designed it?

84jeepj10

lmao, you know when you say it like that it sounds kinda stupid. I was trying to say that the designers of a system don't always think of everything, leave room for improvement, have to cut costs, or just plain don't want to do that with their design. This is one of those mods that some people are doing to try to fill that gap and I wanted to know if anyone has any experience doing it and what the results are. I diddn't mean to sound like I knew better. But your comment did make me laugh at myself quite a bit thanks!

pilotpete2

I have no opinion, too much Ripple has killed off a lot of my brain cells[&:]
Pete

AA5BY

Not and EE and don't know the answer to the question but I'll ask another. One of the reasons that the controller - multi polled motors produce so much power without significant heat is there is very little electro - magnetic drag because the pulses are short and optimal and fire at the most beneficial time to produce power only. So, my question is would adding capacitance lengthen the pulse and manifest some drag and increased heat?

fizzwater2

My Feedback: (61)

caps on the OUTPUT of a brushless ESC would be a bad idea for the reason you've stated - the efficiency comes from the rapid switching and low loss in the ESC.

Caps on the input MIGHT be of some benefit IF they were low enough series resistance, and "fast" enough to respond. Electrolytic caps can be somewhat slow, due to high internal resistance, internal inductance, etc. The wires from the battery to the ESC are inductive - and tend to resist the sudden impulses of current demanded from the input side. Caps close to the ESC can supply these temporary peaks more quickly than the inductive supply leads. I would be inclined to use polyester film type caps to experiment with, most aluminum electrolytics are slow - at least in the world I deal in. Radar transmitters have pretty short pulses, with fast rising edges - poly film caps are used to support the tremendous current demands during the rising edge, larger electrolytic caps will catch up and supply the current demands during the bulk of the pulse.

I doubt if you'd gain enough real world improvement to make it worthwhile, though.

chrisjmartin

My Feedback: (1)

While Fizzwater2 sounds like the guy who really knows, I'll add a comment.

Every device manufactured for the mass market bumps up against the price/benefit wall. If it's too expensive it won't sell. If you don't put good enough stuff in it, you'll get a bad rep and it won't sell. So, engineering is basically the science of trade-offs.

What this means, is that you can probably spend some time and a few bucks improving the performance of a cheap ESC, or you can spend a few more bucks on the ESC to start with and get one with better performance out the gate.

Of course, this assumes that you always get what you pay for. In these days of cheap Chinese products, that may or may not be the case.

84jeepj10

Sounds like this mod was probably more popular with older and/or cheaper ESC's. I could make as good improvements by using shorter battery leads and ones with a lower inductance. I would think that the caps might work for one or two quick pulses but after that wouldn't be able to recharge fast enough to really do any good and would add more load. Thanks for the reply Fizzwater, btw you said you work with radar systems, may I ask where/who you work?

fizzwater2

My Feedback: (61)

The name of the place is Selex - we make the ground end of aircraft nav and landing systems - ILS, VOR, DME, Secondary Radar, etc.

84jeepj10

Nice. I work with the communication systems on military aircraft.

larrysogla

84jeep10,
As I understand it on reading several posts on lengthening Battery to ESC wires(NOT recommended is lengthening ESC to brushless motor wires), the high speed on and off of the ESC while running the Brushless Motor creates unwanted ripple effect and this creates heat which will kill the ESC in the long term. To minimize this ripple effect, it is recommended to parallel install additional capacitors to the Battery to ESC wires. I put as an attachment a previous article on soldering additional capacitors to the Battery to ESC wires. The article was written by a German manufacturer of ESC's, so it is in German but a full and complete translation accompanies every paragraph and the English translation is very accurate. So here goes...........