Ep. 193: Cap Pack Considerations 

Car audio caps would be a good choice if they weren't so dang big. Most effective cap pack on the market fall into two categories. 1) Smaller capacity, but nimble caps can charge and discharge quickly to smooth out individual power ESC pulses. These caps need to pull a lot of current from the batteries following each pulse to be ready for the next one. HOWEVER, if these caps are too large in size, they will not fully recharge in time for the next pulse. 2) Very large super-capacitor packs can "pull up" the battery's voltage without delivering a huge amount of current because of the ESR (Equivalent Series Resistance) of the super-caps and their massive capacity. Since the ESR of the caps limits how quickly they can drain, there is not enough time between pulses for the caps to discharge enough to drop their voltage. These caps retain a voltage very close to the "normal" battery voltage which counteracts the voltage ripple on the battery bus... but they need to be run with batteries strong enough to keep up with the current load of the ESC. Car Audio caps are actually a third category. Since bass tones are only in the 20-200Hz range, they have plenty of capacity to supply current during the "hit" of bass notes, but there is also plenty of time for the cap to recharge during the "valleys" of a bass note's sine wave (as long as the alternator is strong enough to keep up. ESC pulses are much faster than bass notes, so car audio caps might not be able to keep up, so they will end up performing the same as a physically smaller/lighter super-capacitor based pack.

Yessir! www.ebay.com/itm/152897973437

Yup. 4S is "only" 16.8V so you are fine with a little margin for voltage spikes on braking. 25V Caps would work fine up to 5S.

Thanks for watching. And with the fall of the local hobby shop, the internet has become our friend. There are a number of good US based hobby shops that do online sales. Most are on ebay and Amazon. Just limit your ebay searches to North America only (you can do this on the filter section on the left side of the screen. I hope that helps.

A good cap pack might help, but you could just be running up against the internal limits of the ESC. tall gear ratios put a lot of current load on the system at startup... unless you are running a sensored setup.

rhouse21 - RC Physics I geared it back down, no issues now. Thank you for all your knowledge!

I'm still finishing up the latest batch, but I'll probably send you that monster 12-Cap prototype you saw me working on and an 8-Cap-12S version with quick-connectors to see how they compare. I've only built a few of these 12+ cap versions. +Rcman1223 won one in a special event auction I did a little while back and posted this video. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ty69hxWDsBU.htmlm Lamont has a couple, but I'm not sure where the last one went. I'm hoping to see it pop up in a video someday, but who knows.

These caps sit on the main power bus and control voltage fluctuation under heavy throttle that might hurt the ESC. You actually described a glitch-buster cap which does a pretty similar job on the BEC output by helping to eliminate "brown puts" caused by a sudden heavy current load like a digital servo or orher accessories temporarily overloading the BEC circuit.

I'm using a "cheap" meter from Amazon that has a capacitance measurement feature. I love this thing, but was bummed to find out that it will "only" measure caps up to 4,000uF. This is enough to test all of the "standard" caps I cell, but not big enough to handle some of my custom/prototype packs. I'll be picking up a ~$17 dedicated capacitance meter from Amazon shortly that will measure much larger caps, but it only measures caps. I've got some stuff filmed to highlight the difference in performance you can get because of voltage sag from batteries with different Internal resistances (IRs), but I still need to edit it up into a story that makes sense. I also will show how to get a good estimate of your "real world" Internal resistance based on Castle Data Logs. I've done some write-ups about this on my Facebook page if you want a little light reading. ;-) facebook.com/rhouse21rcphysics The thing is that there really is no "standard" way to calculate the advertised C-Ratings. There are some rules of thumb, but the C-Rating is supposed to combine information about the IR of a pack, its ability to shed internal heat (so it won't overheat), and the overall durability of the pack so that a user can know how much power they should reasonably expect out of a pack. As far as I know, Venom is the only company that actually publishes REAL testing data so you know exactly what each series of cells should give you. My plan is to use the Thanksgiving Holiday to make a big dent in my editing backlog, so look for a LOT of new content in the next week.

rhouse21 - RC Physics awesome news I'll be watching

Which vehicle is this in and what is your application. That may factor into the selection of the best cap pack for you.

rhouse21 - RC Physics a XMAXX max5 combo 800kv 25 B&m pinion 35 spur. No cogging on this one. But you are right. I’ve over heated cars that cogged

My pleasure.

Since most guys don't want to void their warranties, I'd advise soldering as close to the circuit board as possible without actually touching it. 😜

First off, thanks for watching! About the Mamba Monster X... the MMX does not have internal current limiting, so it will safely flow over 200 Amps for several seconds. However, it does keep track of how much power is flowing and will pull back on the throttle after a set amount of time to protect itself from overheating. Lots of drag and speed runners who are not familiar with tuning by using their data logs actually have issues with the MMX because they are over-gearing their setups so the ESCs are pulling too much current too fast and they go into thermal protection mode. You can actually squeeze a lot more speed out of this ESC by reading your data logs and practicing a nice smooth trigger pull to minimize current spikes. Also, There's a lot more to cap packs than uF. First off, better batteries will give less ripple voltage, but you should also try to get a cap pack with low ESR (Equivalent Series Resistance). This will let the cap pack charge and discharge more quickly, which will allow it to be more effective fighting voltage ripple.

Deep question! I generally use 8 or 10 gauge wire mainly to minimize the total resistance between the caps and the ESC. The actual amperage coming from a pack should not be very large (maybe an Amp or two per capacitor in the pack), but the time to charge and discharge the pack (also called the time constant) is affected by the total resistance in the system. Lower resistance = faster charging and discharging. This may be a very small effect, but it makes me feel better. The real issue is that Castle tells me that moving the caps farther away from the ESCs makes them less effective at fighting ripple. In addition to ESR (Equivalent Series Resistance) caps also have a parasitic property called Equivalent Series Inductance (ESL) that robs energy from the system. I've been told increasing the wire length between cap pack and ESC increases total parasitic inductance, so the pack cannot perform as well. I haven't worked through all the math to fully understand this effect, but don't worry. I'll post a video if I ever figure that one out completely.

Wow! Thanks for the info man. I myself am into the science/engineering behind these speed car setups. This speed hobby has gotten me to create all sorts of things like a 3d printer. In the near future I might have some content about custom parts and their effect on all the results on speed runs. The math for this electrical stuff is beyond me as of now, but I hope that in college I will really learn how all these systems work. Keep up the content, the more sciencey the better!

Thanks for the comments! I can't believe that I never saw the connection to ESC failures and LiPo failures, but you are exactly right! Great catch!

Frar Dr House21. I am Poppa Phill and very pleased to meet you here. We have much to discuss. I build any number of things purely from scratch but DO NOT POST IT ALL. I was building computers back when you had to spend a month building the motherboard. Yepper we got stuff to talk about young Man! Stay Blessed.

Subbed and Dubbed, Stay Blessed!

hear hear buddy!!! let it have room to breath! Not even for just the electrical side of it. You have two hot runs in a row and your diff fluid is toast...as an example :)

Thank you! I'm happy you enjoyed it. :-D

It's possible. This is part of the reason I always use some sort of quick disconnection on my caps now. If you see strange behavior, you can quickly pull the pack and see if the Cap Pack was contributing to the problem.

It depends on what it's going into, how hard you will be pushing it, and the quality of your batteries. Better batteries nearly always give better ripple voltage.

The answer to that question is yes and no. The cap pack will try to keep the voltage high as long as it's still has a charge in it. The bigger the cap pack, the more electrons it stores, so the longer it will be able to bolster your battery voltage. The challenge is sizing the cap pack appropriately so it gets you over that first hump. I've built packs for 2S racers that they claim really helped their runs. They're listening on my eBay store for around 20 bucks.

@RCPhysics ok so i got a couple more questions for you. Will the cap packs be ok when running lihv batteries? And do you have any videos showing exactly how to install the cap packs? And what size cap pack would you recommend? I'm sure i can get them to small but can you get them to big also? Sorry I'm pretty new to this so I'm just wanting to make an informed purchase before i had over to your ebay site. Thanks for your help

@westsidecracker1 I have built a variety of custi cap packs from small ones for two cell drag cars all the way to Giant custom packs to support a charging system someone was building for their flying field. I'm one of a few guys out there that can actually size packs and build them custom for specific applications. I stepped back from volume production largely because it is difficult to make a profit since there are other good options out there like ripple killers and flow packs. That said, I don't mind doing an occasional custom pack just because I still find it fun to make them. My packs are different than most of the other ones out there because I have figured out how to make them with very low equivalent series resistance. So I personally believe my packs are more effective, but I never gather any experimental data to prove that. The simplest test is whether your daily logs show that your ripple voltage is below 5% or so. Any pack that can do that does the job. 🤓

I believe most people who are doing general bashing and running with healthy, high-output batteries and a quality ESC don't really need cap packs. However, many people have told me that one of my cap packs have improved performance in their cars even in moderate setups. Remember, the main purpose of these devices it's to protect your power system in extreme use cases. If you art that rough when your hardware oh, you are probably okay

If you decide to build your own pack, don't just buy generic caps online. Go to a quality electronics site like Mouser or Digikey and select quality Low-ESR caps with a long expected lifetime. Cheap caps will just blow under the load or simply be ineffective.

@@RCPhysics thank you for that insight greatly appreciated..you video definitely made me look into this alot more

It's probably best for you to send me a message on Facebook and we can work the details there. facebook.com/rhouse21RCPhysics/

My designs have gotten a lot better since filming this video. I am just building them to order now. Here is a link to my ebay listing. My pricing and ordering instructions are in the listing. www.ebay.com/itm/rhouse-Custom-Gen4-Cap-Pack-Built-to-Order-Ripple-Voltage-Suppression-Solutions-/152897973437

...And thanks for the awesome feedback!

Everything you are saying is true and dead on. I think there's a balance between "high performance" and "truly extreme" setups, though. A lot of guys seem to want something that they can dust off and shoot triple digits with and not put a whole lot of thought into it. These guys want "good" performance, but may not have the time or patience to do the things necessary to keep an "extreme" setup happy. Guys like you are REALLY beating the snot out of your rigs, but you also pour tons of time and effort into trying to get every little drop out of your system. There are guys who rebuild diffs, inspect bearings, clean connectors, and test electronics after every outing. These are also the guys who have figured out how to pull 400+ amps out of a Mamba XL-series ESC without turning it into charcoal. As you know, these results usually do not come from one big "upgrade", but from a lot of small but very focused improvements (like shortening up unnecessarily long battery cables, etc.). Thanks for the great comments!

I'm running a "Black Friday" special. $5 off every pack. Just make an offer $5 USD below the current asking prices. www.ebay.com/sch/Toys-Hobbies/220/m.html?_nkw&_armrs=1&_ipg&_from&_ssn=rhouse21&_sac=1

okay I will do bro thank you for ✌ ツ👍

rhouse21 - RC Physics what are the cap packs for

rhouse21 - RC Physics are the cap packs steal for sell on ebay

Terms like "Audio Cap" don't mean anything meaningful in this application. You want to look for high-quality, Low-ESR/Impedance caps with a long rated lifetime. The exact amount of capacitance you will need will depend on your batteries and application. A 2S Street Eliminator with an 80A ESC and new High-C LiPos will need less help than a 6S 200A model running flat out with worn cells. If you go to any of the good electronics components websites, you can pull up a list of all their available caps and sort by ESR, lifetime, and price to find the most cost effective caps for what you are trying to do. generally, larger caps have higher ESR (which makes them less effective), but some brands offer very low ESR cap lines for a little more money. Being able to navigate all that data is how I and the other cap pack makers make money selling these things, so forgive me for not giving away everything. Even though you can save a lot of money building your own cap pack, designing the right cap pack for your application can be tricky and might take a lot of trail and error to get just right. Also, building Cap Packs from scratch can be pretty tedious. While it's not "Rocket Science (says the rocket-scientist), you have to get a lot of details right to make the pack as effective as possible without accidently shorting out you LiPos (which could literally burn down you car). If you do your homework, you should be able to come up with something decent. Or, I could cut you a deal on one of my Gen 4s. 😎 www.ebay.com/itm/152897973437

@@RCPhysics Well there are capacitors that I use to block out certain audio frequencies in various audio applications. Audio caps of various uF ratings that are used to block frequencies and prevent them from being expressed in a certain audio driver that can not handle those blocked frequencies. Ex. Nichicon FG Capacitors 35V 2200uf Audio Grade or something like a Panasonic FM Series Capacitor rated at 35V 1000uf with super Low Impedance

When dealing with audio frequencies, well that is straightforward. I have formulas. This Cap Pack crap is like witchcraft. You need to meter the application while it is running to choose the correct cap uF rating so you can fill the ripple gap. Need a broadcast camera, FPV 5.8Ghz on my boat so I can watch the gap percentage. I don't have Mamba ESCs that can LOG.S So for me, Audio Cap has meaning.

@@UlisesBatalla You are technically correct and I actually spent years analyzing cap packs like audio noise filters on the RC Physics Facebook Page. Then one day I realized that for RCs a cap pack is really acting as power supply noise filters, too. This gives the capacitor network additional overall design considerations than the caps used in pre-amps and noise filters. I'm not saying "Audio Caps" won't work. Good "Audio Caps" tend to come from quality brands with good specs actually. What I'm saying is that you need to look deeper at underlying specs like the ESR/Impedance, current ratings, rated lifetimes, etc. to make sure the cap you are considering is a good match for the money. This will help you to not overpay for an Panasonic "Audio Cap" when a "regular" Kemet or Rubycon would do the job for less money and have a longer rated lifetime.

I small cap pack might actually help depending on your driving style, but you may not get much benefit if you have a well tuned rig. This is because ripple voltage is usually highest at 50-75% throttle. After that, the pulse duty-cycle of the ESC is high enough where the batteries think there is a near-constant flow of electricity, so the ripple voltage falls off accordingly. You are probably spending most of your time at pretty high throttle, so your part-throttle ripple is probably limited to you backing off for turns. Also, better batteries inherently give less ripple voltage, so your 50C race batteries are probably low internal resistance and therefore would be less prone to high ripple voltage. That said, you could try a small cap pack in the 800-2,000 uF range and see if you 'feel" any difference. Some guys claim that it helps their car run cooler and gives more "punch". I have a 3S drag racer who swears by my 4-cap pack and claims it took 0.2 off his drag times.

by meat you mean me? Yes they will benefit you

@@RCPhysics lol...no i meant or should be....benefit me at all...not meat...sorry man,,,where could i buy a few sets of these caps for my program that i explained,,,n yes on//off throttle its oval u no

Thank you!

The best way is through facebook. facebook.com/rhouse21RCPhysics/ You can PM me there. You can also PM through RU-vid, but that's a little clunky.

You can't really choose by cell count alone. It all depends on the current ripple voltage in your system. High powered rigs that pull tones of current tend to have more ripple, but it also depends on the quality of your batteries. Can you tell me about your application? What's your car, ESC and batteries and how do you drive it?

rhouse21 - RC Physics max8 1512/2650kv gen ace 50c 6500mah 2S x2 series 4S OG slash 4x4 on 3.8" Road crushers bashing/high jumps 10lbs Max6 4074/2200kv floreon 3S 35C 2200mah x2 series 6s [only 3s batts I have] Slash LCG on GRP 1/8 S7 speedrun/strip racing 6-8lbs

35C LiPos and "speed running" are a dangerous combination. "Lower-C" batteries generally have more voltage sag under high loads and higher levels of ripple current (which could kill an ESC). Also, a TP 4000-series motor will pull a MOUNTAIN of current (at least on a Castle ESC) and I don't know if a 35C rated battery can keep up without excessive voltage sag and a LOT of internal heating. This could damage the cells and/or ESC and potentially cause a fire. I'm also nervous about the Gens-Ace 50C packs. They will probably do better than the 35Cs, but I do not know what the Internal Resistance and expected ripple voltage levels of those cells would look like under very high current loads. Based on what you told me, I would probably recommend my 12-cap packs or similar for both cars to give the most protection possible... and that you should upgrade to higher C / lower IR batteries as soon as you can. I would also recommend that you begin tuning "by temperature." Happy ESC run cool. Unhappy ones run "hot". It you have a severe ripple voltage problem, the ESC and batteries are probably getting pretty hot. Since the HW ESCs don't support data logging, I really don't know how much current they actually pull in the real world or how likely one of these ESCs would be to fry itself. For that reason alone, I'd recommend a big/effective cap as protection. I'm still out-of-stock, but there are a number of decent packs available out there if you need one fast. If you can wait a little bit, I you can submit a custom order via my RC Physics Facebook or eBay pages.

Thanks, Thunder!. One of these day's I'm going to have to film a video to officially get into the Down & Back Club. ;-)

I build them to order now. Here is my ebay listing. www.ebay.com/itm/152897973437

In principle you are correct. Just as an Olympic diver just jumps into the water. ;-)

I tried to charge the battery of my Camaro once, but the wires I were using couldn't handle the current. That was almost really bad. :-)

Thanks!

Sadly, there are no true standards right now, so everyone is free to come up with their own way of defining things. 😒

Thank you, sir!

There are a number of really good caps out there at reasonable prices. The brands you mentioned are top notch, but I've been using Kemet & Rubycon. Who knows. I might be buying those brands next time I need to resupply. :-D Thanks for watching.

That's how they go in "most" situations, but some guys demand so much ripple current from them in this application that the wires leading into the caps can also fail (burn out). This will cause the cap body to still look perfectly normal, but the cap is dead since the wires into it are basically cut.

I was wondering when those monster prototype packs would turn up! I'm really curious to see that your ripple looked like. Thanks for the heads up! I'm running a Cap Pack photo contest on my Facebook page. Post a pick and tell me how you like the pack. facebook.com/rhouse21RCPhysics/

yea I'll send u a photo of the log.....I'll post a picture in a few hrs

Good analogy!

I guess I was accidentally giving some free advertising. LOL!

rhouse21 - RC Physics I was referring to the noise was horrible

LOL! I didn't even notice. Sorry about that. That pen died right after filming this btw. I guess it was on its way out.

rhouse21 - RC Physics hahah yeah guess we can say it had a screening painful death hahaha.. hey have you tested running a cap pack vs no cap pack .to see if it yield any extra MPH especially in a situation such as a rustler gearedbfor 70MPH in a regular 3s setup

Funny you mention that... I actually started doing some of that testing right before the weather turned cold, but didn't reach my goal before it got too chilly to run. Basically, I'm trying to find the right tune on my ESC. I was doing 3S passes with my Venom 100C 5000mAh batteries with and without an 8-cap (8x470uF) pack, but the batteries will push so much current that my top speeds were being limited by in-run voltage sag. Both configurations ran to the exact same speed, but I saw ~50% reduction in ripple voltage with the cap pack installed. When the weather turns good again, I have some ideas on how to tweak my ESC settings to limit voltage sag and post some better numbers. The word I've gotten from most of my users is that the packs seem to make the ESCs have more "punch" and run cooler. I've got some tester packs out there, so I'm hoping to get some good data logs to review with and without the packs to draw some deeper conclusions about overall performance differences.

LOL!

LOL! It's long gone now! Thanks for watching.

Hahahaha..hate this kind of pen..got ink no ink..