Capasitor Info. how to stop the Ripple

[saming]

hello everyone something that i don't see on the forum. I killed 2 esc with out this info. so enjoy! i have copied this from another forum.
this post is about wire length and capacitor usage and yes everyone should have some for your build.


too long battery wires will kill ESC over time: precautions, solutions & workarounds
... therefore, lengthen the motor wires if possible, not the battery wires.
Also if you run a High Voltage set up your gonna get some spikes. or alot more than u think.
Contents

Problem
Solution
Rules of thumb
Capacitor type
Capacitor polarity!
How to add extra capacitors
Expert/manufacturer opinions, rules of thumb, installation
Explanation/theory
References
Measurements
DIY pictures

Problem
Conclusion from the links below, all controller manufacturers say the same:
Too long battery wires will kill your ESC over time!
The standard input capacitors (large cylindrical thingies in thin shrink wrap) will be destroyed over time because they get warmer/hotter. Using thicker wire will not help, it's mainly a wire inductance problem, not a resistance problem.

This goes for all makes, they all use the same principle (except Sinus controllers, they use sinusoidal commutation instead of trapezoid, they tested 70 meters without capacitors). However, lengthening the motor wires may lead to radio interference. Give the three of them a twist to prevent this.

Solution
Lengthen the motor wires, not the battery wires. That's hardly critical because there's already a lot of wire in the motor itself. If the motor-ESC wire eventually gets too long, it will not harm motor and/or controller. May cause interference though, give the motor-ESC wires a twist. Always a good idea to do that anyway.

Rules of thumb
If you have to lengthen the battery wires, for whatever reason, add extra electrolytic capacitors in parallel with ESC, never in series with ESC. As a rule of thumb, for every 4inch/10cm extra length/distance between battery and ESC, add an 220uF extra capacitance near the controller (electrolytic condensators, voltage the same as the capacitors already installed, low ESR type) (Ludwich Retzbach, German e-flight author&editor, the 'R' in LRK).
Better to use several smaller caps (in parallel) instead of one biggie. Smaller caps can shed more heat and total inductance will be lower (inductance per cap is lower and those inductances are paralled to boot ). See attached pictures below.
Also keep the positive and negative wires as close to each other as possible, eg. by twisting and/or taping them together. If the wires are close to each other then the series inductance will be reduced, because the current is going in opposite directions in each wire (and therefore producing opposite polarity magnetic fields which cancel out). For example, 13AWG wires separated from each other by 1 inch have about 4 times higher inductance than if they are bound together. (Bruce Abbott in http://www.rcgroups.com/forums/showthread.php?p=11594609#post11594609)

Extra capacity based on current and wire length (spreadsheet)
http://www.rcgroups.com/forums/showthread.php?t=952523&page=58&pp=10#post24486468

Capacitor type
The main spec you need is low impedance and low ESR(equivalent series resistance). I think the only thing you will find at radio shack will be general purpose caps, not low ESR. The ESR of a cap won't be printed on it, you will have to look up the manufacturers spec sheet. The Rubicon ZL series mentioned in the Schulze instructions is a good one and is available from newark/farnell. The Panasonic FM series is another good low impedance cap and is available from digikey
http://www.farnell.com/datasheets/2161.pdf
industrial.panasonic.com/www-data/pdf/ABA0000/ABA0000CE108.pdf
PS You would want the voltage rating on the caps to be significantly higher than the battery voltage. Same voltage rating is the installed caps. Higher rating is no problem. (thanks jeffs555, from http://www.rcgroups.com/forums/showthread.php?p=11971048#post11971048)
If you try it with longer wires and no extra low esr caps it may work for a while, but the longer wires put an extra load on the original cap. The extra load shortens the life of the original cap and it will eventually fail, probably catastrophically. (thanks jeffs555, from http://www.rcgroups.com/forums/showthread.php?p=11996840#post11996840.


Capacitor polarity!
Electrolytic capacitors, like batteries, have a (+) and (-) lead! Solder them in the wrong way and they will got hot, pop open or even explode. Nasty fumes and the liquid stains. Don't ask how I know

How to add extra capacitors (English and German)
http://www.matthias-schulze-elektronik.de/guide/gfutc-de.pdf (English)
YGE controllers, extra capacitors and their location, nice pics, click to enlarge:
http://www.yge.de/caps2.php

Expert opinions, rules of thumb, installation
Schulze controllers and battery lead length
http://www.matthias-schulze-elektronik.de/guide/gfutc-de.pdf (English)
Castle Controllers about battery lead length
http://www.rcgroups.com/forums/showpost.php?p=1537846&postcount=28
http://www.rcgroups.com/forums/showpost.php?p=4833040&postcount=5
http://www.rcgroups.com/forums/showpost.php?p=1531363&postcount=25
http://www.rcgroups.com/forums/showthread.php?t=1095329
Bob Boucher (Astrobob, http://www.astroflight.com) on long battery leads
http://www.rcgroups.com/forums/showpost.php?p=2988042&postcount=32
Hacker on long battery wires:
http://www.rcgroups.com/forums/showthread.php?p=11297012#post11297012

Explanation/theory
First a watery analogy, water running in a pipe and through a tap. Now turn off the tap quickly. You'll hear a loud knock/shock sound in the pipe. The water wants to continu flowing but it can't, for a moment the water pressure is much higher than the static water pressure. It's the same for a current that's switched off, because of the inductance it wants to keep on flowing, voltage gets higher. This is also what causes sparks (brush fire) in a brushed motor.

The controller is like a watertap that's switched off (and on) very fast (8,16, 32kHz PWM) to get the desired current. Turning off the current, in combination with the battery wire inductance, causes voltage spikes because the current wants to continue on its course (ref. inertia of the moving watercolumn). Those voltages are higher than the battery voltage. The input capacitors (cylindrical) takes care of these spikes (they reduce the wire inductance). The longer the wires, the higher the voltage spikes induced in the wires, the harder on the input capacitors. They will get warmer, heat up and explode. This is caused by the wire inductance, not by wire resistance. Therefore, using thicker wire will not help much, it's not a bad idea either, but extra capacitors are the solution, thus reducing/compensating the wire inductance. Or longer motor wires instead of long battery wires.


capacitor you may use or recommend from spinningmagnets
http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=22194&start=25#p382837

Here are the three cap choices I had selected after much study and searching. When comparing cap choices, impedance/ESR should be as low as possible, and amps (ripple capacity) should be as big as possible (dont ask me why they list it that way). The lower the voltage rating, the better the performance specs are, but if the cap voltage is too close to your systems top-voltage and it spikes up over the cap rating, the cap will pop open like popcorn (also if you plug it in backwards...don't ask how I know that).

I'm told the uF number (physical size) of the cap doesn't help us at all (bigger is not better), its only the other numbers that are of concern.

12 mOhm, 4.28A, 35V, 3900uF, http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=493-1602-ND
16 mOhm, 3.32A, 50V, 1000uF, http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P12393-ND
17 mOhm, 3.50A, 63V, 1800uF, http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=565-1731-ND
26 mOhm, 3.86A, 100V, 820uF http://www.digikey.com/product-detail/en/100ZLJ820M18X40/1189-1048-ND/3133977
27 mOhm, 3.51A, 100V, 680uF http://www.digikey.com/product-detail/en/100ZLJ820M18X40/1189-1048-ND/3133977

Or you can go the castle creation route 25$ worth it or you can buy your own connectors for like 2 bucks each.

CC CapPack is useful in all brushless motor applications, where it serves to give just that little boost needed to overcome ripples in the battery voltage caused by hard acceleration or long battery wires. Remember, ripple voltage is hard on an ESC, adding the CC CapPack can help reduce the load on the controller's on-board capacitors.

Helis: CC CapPack is highly recommended for all 500 class and larger heli applications where Y harnesses and long wires can bleed voltage and hard collective pulls can strain even the most powerful batteries.

Cars/Trucks: With their high torque requirements – going from 0 to 100% throttle isn't easy on controllers or batteries - RC cars and trucks put enormous loads on brushless power systems. Use CC CapPack to help your system power through the abuse.

Aircraft: Larger electric power systems lead to larger electric powered aircraft, and sometimes the distance between the battery pack and the ESC grows beyond the length of the wires installed on the components. Adding wire also adds inductance, which can increase the ripple voltage in a system. CC CapPack essentially negates the ripple caused by the addition of up to 8 inches of length to the battery wires.

CC CapPack is designed for quick and easy installation. Users simply cut the soft silicone insulation on the battery wires – do this as close to the ESC as possible – and place the exposed wires in the channels on CC CapPack's posts. Check for proper polarity and then solder the wires to the posts. Use the included heat shrink to finish it off for a professional looking install.

Note: All Castle controllers with data logging capabilities can report the ripple voltage they encounter during use. Ripple voltage peaks should always be less than 10% of the total pack voltage; the smaller the ripple voltage the better. If an application exhibits more than 10% ripple voltage under peak loads, the user should consider using higher discharge (C Rating) batteries, shorter wires, higher current connectors, better gearing or a smaller load.

Multiple CapPacks may be used in an application. They should all be installed as close to the ESC as possible.http://www.castlecreations.com/products/cc-cap-pack.html#

Thx again for everyone help and know how

 

[beto_pty]

nice addition to the knowledgebase... getting ready to order come capacitors from digikey as we speak...

 

[Carbon]

Although I read your explanation on the theory of why extra capacitors would be helpful, why not a single high voltage capacitor with a large amount of capacitance? Also, have you done this to your own board? Did you notice any realistic difference? I thought that the manufacturer should know how many caps to put.

 

[spinningmagnets]

For some reason that I don't understand, the lower the voltage, the better the capacitor suppresses ripple. The milliOhm number is the resistance, lower is better.

The amp number (3.32A for the most recommended 50V unit), well...I don't know what that means but Jeremy Harris and Fechter and some electronics guys said the bigger that number is the better.

As far as the number of capacitors that the factory "should know" to install already. They designed the proper number of capacitors for running these ESCs on a model plane/helicopter with average flying intensity. If you are going to do acrobatics with your model craft, they have the $25 "extra capacitor pack".

I'm not experienced with electronics, but there was a time when a bunch of electric bike builders were frying a lot of expensive ESCs (Castle HV-160's). They started adding extra capacitors, and the frying stopped.

 

[saming]

to be honest i dont know ether But what i do know is i have 2 fried esc and it fried cause the current problem the ripple. i dont have data logging to test this theory but if you run something silly like 10s its nice to have a fail safe. I was only advise im not a scientist Just someone passing on knowledge. Even tho you might not understand what that means or what it does cause its beyond me. i do know that it helps stop ripple spikes and it helps with the long wires if you do have long wires. they wouldnt make them if you didnt need them. it explains it self if you buy the castle caps

 

[torqueboards]

to be honest i dont know ether But what i do know is i have 2 fried esc and it fried cause the current problem the ripple. i dont have data logging to test this theory but if you run something silly like 10s its nice to have a fail safe. I was only advise im not a scientist Just someone passing on knowledge. Even tho you might not understand what that means or what it does cause its beyond me. i do know that it helps stop ripple spikes and it helps with the long wires if you do have long wires. they wouldnt make them if you didnt need them. it explains it self if you buy the castle caps

Are you sure you are connecting your setup properly? If you fried 2 ESCs? I've tried cap banks and didn't find them quite useful as most mention. Doesn't hurt to have it too much but isn't required either imo

 

[saming]

when both my esc fried i put the max volts i could to them and i can only assume it ether got over amped, if theres to much of a load on the esc as in going from slow to fast rapidly, you may not geared correctly. or if your batteries cant handle that load it cause spikes or if they are improperly balanced. thats what the other web forums say but i cant test that for sure i dont have data log but i got a castle creation esc coming so i am going to put it though the test. and get back to you with all the info i can.
Thx again for the Input guys I'll post more after my esc arrives Monday.

 

[Lebowski]

For some reason that I don't understand, the lower the voltage, the better the capacitor suppresses ripple. The milliOhm number is the resistance, lower is better.

I think these typs of caps are made as two narrow sheets of material rolled up together with electrolite between them. The narrow strips of material have a certain length giving it resistance, the esr.
Now, the higher the voltage the stronger the field inside the cap. To make sure it doesn't punch through, in high voltage caps the electrolite is thicker, the sheets or plates are further apart. But plates further apart means the capacitance is reduced, which can be compensated for by increasing plate area, or in this case increase the length of the narrow sheets of material. The longer length then means resistance goes up...

 

[Matt Gruber]

saming
thanks for this info!
i'm going to tidy up the wires on my -9 scooter. there is nearly a foot of extra battery wire, and it is more than an inch apart. A FREE upgrade!

 

[Carbon]

Now, the higher the voltage the stronger the field inside the cap. To make sure it doesn't punch through, in high voltage caps the electrolite is thicker, the sheets or plates are further apart. But plates further apart means the capacitance is reduced, which can be compensated for by increasing plate area, or in this case increase the length of the narrow sheets of material. The longer length then means resistance goes up...

I think the word you are looking for is "dielectric". I think from my high school course we used this formula:

 

[liveforphysics]

The ESR is of course very important, but the ESL is equally important depending on the speed of the voltage spikes you're attempting to clamp. The rising edge of the switching on controllers is easily in the Mhz range, even though the carrier frequency itself is only ~16-30kHz.

Large low ESR electrolytics are fantastic for the larger pulses, but completely transparent to the stuff in the Mhz range.

Throw in an ultra low ESL/ESR snubber as well to have a wide-frequency noise clamping for optimal performance.

Something like big flat lead polypropylene and foil cap would catch the stuff that the electrolytic's can't filter.

 

[saming]

880uF (4x220uF) @50V is the configuration for the castle creation cap pack. from my forum lookup.
http://helidirect.com/images/helicopters/electronics/brushless_escs/castle_creations//CCCapPack2.jpg

 

[Matt Gruber]

saming
i took out a whopping 21" of +
8" of neg
and 10" between the 2 tool packs (in series)
39" total awg14 NOW REMOVED!
10s2p
+ and neg are almost equal now, and next to each other.
what do you think? those long wires could explain why 3 esc's failed in 2 weeks! now they are normal length.

 

[liveforphysics]

880uF (4x220uF) @50V is the configuration for the castle creation cap pack. from my forum lookup.
http://helidirect.com/images/helicopters/electronics/brushless_escs/castle_creations//CCCapPack2.jpg

That design seems minimally useful in my perspective. Yes it would be better than no additional caps, but it's transparent to higher frequency noise.

 

[saming]

Agreed Its only suppose to help your already installed capacitor on your esc so you don't burn it up on hard acceleration or long wires or the main point having crappy batteries Learn from my lesson 4 bucks saves hundreds burned 2 esc in 2 weekend not fun.

 

[Rosco]

I have on Samings and someone else's suggestion installed a DIY cap pack on my RRBs board with batteries being held in a backpack rather than on the board for a cleaner and lighter board.

I wired in 4 x 1000uF 35v Low ESR electrolytic with 6 x 600uF 35v ones giving a total impedance of 6600uF at 35v on a 22.2 nominal voltage build. I wired them in parallel as close as possible to the board on the 5' long extension cord connecting my packs to the board.

Haven't had an issue since.

 

[JackHMcD]

⏆⏆⏆⏆

 

[saming]

Correct that the Optimum recommended location

 

[RomeoEG]

880uF (4x220uF) @50V is the configuration for the castle creation cap pack. from my forum lookup.
http://helidirect.com/images/helicopters/electronics/brushless_escs/castle_creations//CCCapPack2.jpg

That design seems minimally useful in my perspective. Yes it would be better than no additional caps, but it's transparent to higher frequency noise.

So what would you recommend, perhaps in addition to the castle creation cap pack mentioned here, to deal with the higher frequency noise (mHz)? Links to an actual product I can order and slap on my board would be great

 

[spinningmagnets]

I assume it would still be a good idea to have the caps to 6-inches of wire from battery to ESC, or do I not have to worry about that short of a length?

The three wires from the controller/ESC can be as long as you want. The two wires from the battery to controller should be as short as practical, and the extra caps should be mounted as close as possible to the controller.

 

[torqueboards]

I assume it would still be a good idea to have the caps to 6inches of wire from bat to esc , or do I not have to worry about that short of a length?

The three wires from the controller/ESC can be as long as you want. The two wires from the battery to controller should be as short as practical, and the extra caps should be mounted as close as possible to the controller.

If the wires from the battery to the controller are pretty short about less than 4-5 inches. Is it still necessary to use caps? I've added the caps to my setup but didn't notice anything significant.

 

[RomeoEG]

Bruno at Alien sells nice capacitor banks as well.. not as clunky as the castle cap packs (though the castle ones look like a good bet too)

http://alienpowersystem.com/product-category/rc-ev-accessories/electronics/

I'm still interested to see what liveforphysics says about the high frequency noise in the mHz range..