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Capacitors
has anyone logged peak current before and after an upgrade in capacitors? we dont appear to use enough capacitors to do anything but filtering. Im not suggesting anything im just curious. When developing very high speed motors that are continuously accelerating and decelerating capacitors (the size of the ESC) are designed into the system to capture the regenerated energy (braking) and then return most of it to the next acceleration cycle. I can calculate the amount of regen energy to determine the capacitor size but I’d like to see if anyone has a before and after current log? It couldnt be a log from the ESC it would have to be from something like the eagle tree placed before the capacitors on the battery side. what it does is minimize the peak load on the battery and minimizes the peak regen to the battery. Looking at the log that first monster jump in current is very minimal. You would also not see the current spikes when transitioning quickly from one rate to another. I dont think you would notice it in motor performance other than slightly more efficient transitions. The battery wouldnt be pushed into its continuous rating as often. |
Lots of people do feel a difference when ony "tuned" is engraved on the motor..... The fooling of the mind is stronger than a real feeling.
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and the reason... an electronic voltage amplifier is not used...
I designed one in the mid 1990's.. cost and weight overwrote the added power. |
So I was always under the impression that the capacitors were just to filter the noise that apparently feedback into the receiver and cause all sorts of issues
I remember seeing a YouTube video of someone testing larger capacitors and it made no difference Are you suggesting trying a really large capacitor.? Not sure if there is enough energy generated off throttle to make it any use, but I am intrigued by the idea |
Originally Posted by chuck_thehammer
(Post 15380279)
and the reason... an electronic voltage amplifier is not used...
I designed one in the mid 1990's.. cost and weight overwrote the added power. |
Originally Posted by Bry195
(Post 15380411)
not a bad idea. Electronics have come a long way |
Originally Posted by Bry195
(Post 15380206)
has anyone logged peak current before and after an upgrade in capacitors? we dont appear to use enough capacitors to do anything but filtering. Im not suggesting anything im just curious. When developing very high speed motors that are continuously accelerating and decelerating capacitors (the size of the ESC) are designed into the system to capture the regenerated energy (braking) and then return most of it to the next acceleration cycle. I can calculate the amount of regen energy to determine the capacitor size but I’d like to see if anyone has a before and after current log? It couldnt be a log from the ESC it would have to be from something like the eagle tree placed before the capacitors on the battery side. what it does is minimize the peak load on the battery and minimizes the peak regen to the battery. Looking at the log that first monster jump in current is very minimal. You would also not see the current spikes when transitioning quickly from one rate to another. I dont think you would notice it in motor performance other than slightly more efficient transitions. The battery wouldnt be pushed into its continuous rating as often. Conundrum: Any capacitor with a low enough ESR to make a difference that fits in an RC car won't have enough capacity to make a difference. Super capacitors have the capacity but such a high internal resistance they won't do anything. Another point that many neglect to consider is that any current you get out of the capacitor had to come out of the battery, thereby reducing it's voltage to some degree. Plus you can't drain the capacitor any lower than the battery voltage so all the current used to initially fill up the capacitor is lost to the system. It's not much, but since there is essentially zero benefit, the cost/benefit ratio is not in your favor. There are electric energy storage and release systems but they are more than just capacitors. |
That makes sense and you have saved me some time.
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Remember, Thinking outside of the Box,,, is NOT a Bad Thing...
but most do not have a good up-side.. but the "FEW" are winners. I spent several Fun years.. designing electronic battery dischargers... Excel spreadsheets, Macintosh computer, a/d and d/a converters to MAP discharge voltage and amperage..constant current...regulated. 10 samples per second. long before Turbo30/35 came out. using calibrated equipment., National Bureau of Standards. when everyone else were using a bank of car brake light bulbs or big resistors.. I had a black box with vented heat sinks... 2 LED's and 2 switches.. and a label that said "H O T".... with auto shutoff based on battery discharge voltage. 30 amp regulated. +/- 0.1amp |
Originally Posted by chuck_thehammer
(Post 15380934)
Remember, Thinking outside of the Box,,, is NOT a Bad Thing...
but most do not have a good up-side.. but the "FEW" are winners. I spent several Fun years.. designing electronic battery dischargers... Excel spreadsheets, Macintosh computer, a/d and d/a converters to MAP discharge voltage and amperage..constant current...regulated. 10 samples per second. long before Turbo30/35 came out. using calibrated equipment., National Bureau of Standards. when everyone else were using a bank of car brake light bulbs or big resistors.. I had a black box with vented heat sinks... 2 LED's and 2 switches.. and a label that said "H O T".... with auto shutoff based on battery discharge voltage. 30 amp regulated. +/- 0.1amp if someone has some before and after data even if your not sure what you are looking at you would be respected for the effort even though We don’t suspect allot of positive. It would be very beneficial if there was. if I had a nickel for every failed idea...the benefits to exploring bad ideas are are greater than the sum to the guy on the adventure and a way for old guys to give back what they got when they were a whipper snapper. |
Just an example: Google "super capacitors esr" and one of the pages you find is something titled:
DGH Supercapacitors offer massive capacitance, low ESR."I picked one set of parameters to look at: max voltage and 1 Farad capacitance. The max voltage these support is 5.5V so you would need two in series for use with a 2S LiPo pack. Their idea of "Low ESR" in a super capacitor is 500 MilliOhms for DC current. With 2 in series that would be 1000 MilliOhms A good battery has a resistance of 2-4 MilliOhms. The max current rating for the Super Cap is 1.8333 amps. Since they are in series, that's still the current limit. LiPo batteries can put out 100 amps. Can't see how anyone could look at these numbers and think these would be better than, for instance, going up 2% in battery capacity. If one were to install these in a car, the first time you give it full throttle would essentially be a dead short as far as the capacitor is concerned. I don't know what would happen, but it probably wouldn't be good for the capacitor. The only thing that might save the caps is that the battery voltage didn't drop very much so the caps won't see a large enough voltage drop to discharge much current across the short, in which case they won't be doing anything anyway. |
Originally Posted by ta_man
(Post 15381142)
Just an example: Google "super capacitors esr" and one of the pages you find is something titled:
DGH Supercapacitors offer massive capacitance, low ESR."I picked one set of parameters to look at: max voltage and 1 Farad capacitance. The max voltage these support is 5.5V so you would need two in series for use with a 2S LiPo pack. Their idea of "Low ESR" in a super capacitor is 500 MilliOhms for DC current. With 2 in series that would be 1000 MilliOhms A good battery has a resistance of 2-4 MilliOhms. The max current rating for the Super Cap is 1.8333 amps. Since they are in series, that's still the current limit. LiPo batteries can put out 100 amps. Can't see how anyone could look at these numbers and think these would be better than, for instance, going up 2% in battery capacity. If one were to install these in a car, the first time you give it full throttle would essentially be a dead short as far as the capacitor is concerned. I don't know what would happen, but it probably wouldn't be good for the capacitor. The only thing that might save the caps is that the battery voltage didn't drop very much so the caps won't see a large enough voltage drop to discharge much current across the short, in which case they won't be doing anything anyway. |
Bry195, Thank You for the nice comments.
I do not see a 'real' benefit going down the capacitor road. ( I could be wrong ). a quality speed controller.. is just that.. with little needed to improve it from the outside of the case. good battery, good connectors, good wire at the correct size for amperage, proper mounting.. even some vibration isolation for controller and maybe battery. a modern speed controller is like an electronic variac but for DC.. as it's "ON" resistance is almost zero, with software programming to control is operations if the factories did NOT have US install the capacitor .. and it was mounted inside the case.. this conversation might not be happening. long time ago... we changed / upgraded / replaced damaged FET's inside the controllers all the time. Have a Great Day. |
Originally Posted by Bry195
(Post 15381488)
You went really deep really quick. I dont know how you go from the basic mechanical watt seconds in and watt seconds out peak and continuous. If I try hard enough I can calculate what the mechanical system creates but I keep hearing all kinds of noise about c ratings and peak versus continuous but nothing definitive. http://www.hobbytalk.com/bbs1/showpo...6&postcount=45 |
I thought people understood that caps arent batteries. Can you talk about the math behind a capacitor that is capturing the regenerated power from a deceleration followed immediately by an acceleration? Stuff that happens at 100ms instead of seconds. I think you made a great case for getting a better battery for low frequency response (corners...) and im not saying that means you are wrong for high frequency application. Peak current use on a battery or dc bus takes away from the continuous available bus. It also generates heat. Regenerated current also creates heat.
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