Ep. 269: Cap Pack Wiring Tip 

Thank you!

Thank you for the compliment! Copper Craft wire is an AWESOME idea to take my suggestion to the next level! Wow, I haven't even thought of vacuum tubes in years! LOL!

Thank you! I really appreciate the good words. 😎

Thanks!

Cap packs only charge up to the voltage of the battery they are connected to. A 100V cap plugged in parallel to a 2S battery will only charge up to the voltage of the 2S pack (nominally 6-8.4V). That said, adding a cap pack to a 4S setup (1 4S pack or 2 2S packs in parallel) will probably give you more "punch" and help your ESC run a little cooler.

Thanks! LOL!

Thanks!

Thanks!

Thank you! And thanks for watching. 😁

The wire is actually really strong and the exposed section becomes extremely stiff once you apply solder to it. So as long as you do a good job soldering, you shouldn't have to worry about the wire being weakened. This is also why I make my new cap packs to be hard mounted to the chassis to reduce the stress on the wires. Thanks for the great comment.

A 35A ESC will probably peak at 50-75A under max load. Assuming decent batteries, you are probably going to get a max a of ~0.5 - 1hp out of that setup.... if your ESC can actually keep up with that load. In my experience, cheaper ESCs usually need a lot more help than more rugged ESCs because they just aren't designed to take a lot of abuse. for that reason, I'd build a pack with at least 4 low-ESR caps in the ~500uF range. If you are sticking to 3S, there is no benefit in running caps rated for more than 15V unless they have a lower quoted ESR/impedance that justifies the price difference. Here is an article with a ranking of capacitor brands. If you stick to Tier 1 or Tier 2 brands and assemble with high quality wire (I'd go with 14AWG, 12AWG, or larger), you will end up with a really solid pack. www.tomshardware.com/reviews/power-supplies-101,4193-5.html

@@RCPhysics thanks for that reply I will do! One more question. How would 4 500uf capacitors compare to 2 1000uf capacitors? Would it be the same or is there a benefit? Also why not use a higher voltage vs 14v. Would that matter at all or do you want it to be as close to the battery max voltage for some reason?

Here is an article I wrote a while back explaining ESR (Equivalent Series Resistance). facebook.com/rhouse21RCPhysics/posts/773378892833621 The short story is you want as low an ESR on your Cap Pack as possible to make it be more "effective". 4 500uF packs in parallel will usually have a lower ESR than 2 1000uF, but you have to read the spec sheets of the caps you are planning on using to confirm this. Sometimes good cap makers will have ultra-low-ESR caps that will break this rule-of-thumb, but you will usually pay more for them. As for cap voltage rating, capacitance is defined as the number of electrons that a capacitor will hold at a given voltage. In this way, they act like a water tank and need to be a certain physical size to hold a certain number of electrons. No matter the voltage rating of a cap, it will only store a certain number of electrons at a given voltage, so a 15V, 50V, or 1,000V cap of the same uF rating will all contain the same number of electrons at 12V (3S). Buying a higher voltages cap just makes sure it has "room" to store more electrons at the higher voltages. In practice, you really just need a high enough voltage rating to handle your max battery voltage. Buying higher voltage just give you more room for electrons that your system will never try to store.

I'm wondering what the cap pack does bc I ordered a hobby wing combo and it comes with a cap pack

That's not the best idea for a brushless motor. It would interfere with the ESC pulses.

Here's a video describing how a Cap Pack works. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ie8P3ocN1io.html

Keep us posted.

It really depends on the ESR (Equivalent Series Resistance) of the caps and how many you plan on using. Generally, larger capacity caps from a given product line have higher ESRs, but this is not always the case. You should refer to the manufacturer's data sheets to see which is the best option.

@@RCPhysics I was looking at Philips ones and was planning on making one for a 4s system and a 2s/3s

@@plproductions8887 What ESC are you using? That will determine how much uF total you need for the pack. If it's something like a ~100A-class ESC, you shouldn't need much more than 1,500-3,000uF so 4-6 470uF high quality caps would probably do just fine.

@@RCPhysics one is a castle mamba x run on 3s and the other is a HPI trophy Truggy Flux stock esc on 4s ( there Panasonic M Serious Low ESR ) sorry

@@plproductions8887 Che the data logs on the Mamba X to see if you even have a ripple problem. That ESC caries a lot of onboard capacitance for its size, so you may be pleasantly surprised. It's probably go with 4-6 470uF caps for the HPI, though.

Honestly, I've never run the hobby wing ESCs so I'm not sure how much difference there is between the two you mentioned. Generally motors will pull a little more current on larger ESCs, even if just for a few moments, so upping the ESCX size can often remove a power bottle neck if you are trying to get more out of your system. I'm a big advocate for data logging ESCs for speed and drag applications simply because they take the guess work out of tuning. You know exactly what the setup did which helps you figure out what to do next to move forward. That can actually save you a lot of time and money so you aren't running down tuning dead ends.

They are fine there. Caps don't make much heat. ESCs have some am ount of caps already inside, but adding a Cap Pack just gives them more protection for extreme setups.

@@RCPhysics I mean heat from soldering gun

Just use a high wattage iron and be careful not to let the wires get too hot. Castle uses high temp solder in their ESCs, so it would take a LOT of heat to damage the ESC..., but it's not impossible.

Cap pack do the most good in very high current applications, like drag racing, speed running, or bashing with heavy cars. However, a good cap pack can increase the life of most highly loaded ESCs by taking some of the load off of the on-board caps. They can also often mahe the ESC run cooler and a bit more efficiently.

Thanks for the great comment! A military splice works great with normal wire, but I see 2 problems trying to use it for this application. 1) RC ESCs typically use 8-12 gauge silicone wire, which is extremely thick and does not like making very tight bends without trimming down the overall wire diameter (which defeats the purpose of using the thicker wires). 2) This flexible wire is..... very flexible. It is actually made of an incredible number of tiny strands that move more like thread than normal wire. As a result, it doesn't like to hold a shape like solid core wire would. I'm sure you could figure out a way to make a military splice work, but a little piece of wire like a bread tie or copper hobby wire is a lot simpler.

Oh, and I chose Deans for the quick connections because they are 1) capable of easily handling 60A of continuous current, 2) really compact, 3) really reliable, and 4) really inexpensive. Even the best individual caps of this type are only rated for a few Amps of ripple current (1-4 Amps) during continuous operation (discounting the in-rush current at power up). That means that a Cap Pack with 12 caps would see a continuous flow of less than 50 Amps and that would only be on a system with a HUGE amount of ripple voltage. "Normal" operations on a well tuned setup should be much lower. This makes the Dens connectors really well suited for the job. BTW, The reason I use really thick wire through the cap packs is to limit the electrical losses between the cap pack and the ESC. I believe the fatter wires buys you a little flexibility in mounting the caps. Too much thin wire in between the caps and the ESC makes the Cap Pack much less effective. Lastly, my newest designs integrate the quick connector into the body of the Cap Pack. This makes wiring them much easier and the quick connection virtually disappears visually. Some guys would like to use their favorite connector for the quick connection, but that would require me to have different designs integrating each of the major connector types to house connectors that would be used really infrequently since I build my caps to be hard-mounted to the vehicle chassis.

@@RCPhysics what about my ESC 150A battery 4S what is cap pack for my setup?

@@jacksonjoss1108 Which ESC and what car?

@@RCPhysics flycolor esc rc boat rigger

Definitely! I've goylt a few EDF guys using my packs.

Their voltage is good (6S is only 25V) but, you have to be really careful with large caps. Many very large caps have high ESR (Equivalent Series Resistances) so they could take much longer to charge and discharge than smaller low-ESR caps, so they may be less effective overall. Assuming they are brand name caps, you may be able to look them up on their manufacturers website and find their data sheet. A high performance 6S LiPo setup will have an Internal Resistance (IR) ranging from ~5 - 30mOhms. If your 2 caps in parallel have an ESR of around the same level or lower, they should provide a good help to the main batteries keeping the ESCs fed. However, if the caps are much higher resistance than the batteries, they may not be able to keep up with the load and may overheat and blow.

I build them to order now. You can find a listing showing options and prices here. www.ebay.com/usr/rhouse21

I recently discovered that Radio shack is still around. They are just online now. So you can still order the good solder and all the other Radio shack products you like through the internet. Also I like to use liquid tape to cover the wires instead of heat shrink. In my opinion it does a better job of keeping the dirt from the road from getting into the connections.

Naah. Liquid tape solidifies into a silicone rubber that is good for over 200 degF (100 degC). If your wires are getting that hot, you have other issues to deal with in your power system. 😎

@@RCPhysics just looks like a sub par solder job, that's all. GL

I use silver solder on all of my power wires because it is a lot more durable. The downside is it looks really ugly. It also takes a lot more heat to melt which means you have to use a pretty powerful soldering iron to get it to melt well on thick power wires. That said, these were not my prettiest solder joints which I fully admit.

@@RCPhysics noted and appreciate the info. what wattage iron if you don't mind me asking.

I used to use a 150W Weller, but that sucker is hard to be precise with. I recently switched to a "budget friendly" (translation: cheap) temperature controlled solder station from Amazon that lets me use Weller-compatible iron tips. This lets me pick the right tip for the job. I can use a fine tip and low temp solder for circuit boards then switch to a massive chisel-tip that retains a lot of heat energy to heat the solder joint quickly, melting the high temp solder before the rest of the part/wire heats up.