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Old Apr 07, 2012, 12:50 PM
Capt. Z
falcon5's Avatar
United States, NV, Las Vegas
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Thanks Ron, Great info!!! Man what would we do without RC Groups.
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Old Apr 07, 2012, 01:14 PM
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Florida
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Quote:
Originally Posted by Ron101 View Post
In some models there is no room or cooling for the ESC.... so the ESC is located in the tailcone of the fan for good cooling, this leave long leads to the packs
So you are saying that it is a physical limitation and not an electrical one, right?
If a model did have enough room and cooling to locate the ESC near the battery, it would be the preferable way, right?
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Old Apr 07, 2012, 01:27 PM
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Brentwood, California
Joined Jul 2007
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Quote:
So you are saying that it is a physical limitation and not an electrical one, right?
If a model did have enough room and cooling to locate the ESC near the battery, it would be the preferable way, right?
Correct...it's physical
In my spark I have a Stu Max 110-52 it's a pusher fan... you can't put the esc behind the fan. So I have it moved forward...added a small fan and a naca duct. Still added one of tams small cap packs.... all has been well for 100 some odd flights (stopped counting)

Now in my F-18 space is tight, I have no where to bring in cool air, lots of hot packs warming in the fuse.... not a good environment for the ESC

I'm running two of Tams full size dynamax conversion (128mm) with Ice 160 HV 2 in the tail cone...his center body design puts 200 mph air right over the ESC..... BVM also does this...so we can't deny that having the ESC behind the fan works well. I'd say these two companies have more air time with large expensive jets than any of us

With that said I still feel that both ways can work well if thought out well...I've had great success doing it both ways
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Old Apr 07, 2012, 01:48 PM
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Quote:
Originally Posted by Ron101 View Post
Correct...it's physical
In my spark I have a Stu Max 110-52 it's a pusher fan... you can't put the esc behind the fan. So I have it moved forward...added a small fan and a naca duct. Still added one of tams small cap packs.... all has been well for 100 some odd flights (stopped counting)

Now in my F-18 space is tight, I have no where to bring in cool air, lots of hot packs warming in the fuse.... not a good environment for the ESC

I'm running two of Tams full size dynamax conversion (128mm) with Ice 160 HV 2 in the tail cone...his center body design puts 200 mph air right over the ESC..... BVM also does this...so we can't deny that having the ESC behind the fan works well. I'd say these two companies have more air time with large expensive jets than any of us

With that said I still feel that both ways can work well if thought out well...I've had great success doing it both ways
Thanks. I am working on a large Lear that has plenty of room in the forward fuselage. I am thinking of using a small PC cooling fan to keep the batteries and ESCs cool. Let's see how that works out. I will do some temp measurements at WOT and will post.
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Old Apr 07, 2012, 02:22 PM
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[quote]...Well the FETs are the end result of a problem and you are correct in saying that they should be better but, that costs money and the ESC market is very competitive...[/quote ]

...the quality us good but they are out of spec. There are less quality fets that handle transient power better.

Its also unusual to have this many similar experiences with the device goin wrong...its.not the mcu, regulator or onboard caps that are failing
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Old Apr 07, 2012, 02:31 PM
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I think your confusing the issue of the thread, the thread is about adding caps for extended battery wires which has nothing really to do with castle's recent recall problems even though not running caps may or may not exacerbate the problem
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Old Apr 07, 2012, 02:49 PM
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Quote:
Originally Posted by falcon5 View Post
OK peacemakr40 I have the mother of all installs going here. Curious as to what an EE would suggest about it,

Considerations for adding cap banks:
1 - what level of filtration do you want to achieve? = A good level
2 - What is your source voltage and C rating? = 10S per fan . 30C batts
3 - How many Amps are you pulling under full load? = 120amps per fan
4 - How long are the wires from the battery to the ESC? = 45"
5 - what is your weight limit ( some filter caps can weigh quite a bit)? = No real limit
6 - How much room do you have to work with near your ESC? = allot

And the vedict is????
Based on what you've stated, I would build up a Cap bank of the following:
6 - 1000-1500uf 63V Low ESR Electrolytic caps
2 - 220uf 63V Low ESR Electrolytic caps
2 - 1uf 63V Tantalum
1 - .1uf 100V ceramic.
All caps are in Parallel. The electrolytics should be at least 105 degrees C, if you can find them, get 130 degree C caps.
Leave 2mm between all caps for airflow to cool.
Place the smaller electrolytics and tantalum as close to the ESC as you can. You can strap the .1uf Ceramic on the bottom side of the board.

Based on my calculations, this should give you a .03V P-P ripple under full switching load at 12KHz (center freq of 8-16 KHz)
If designing a circuit board for these, use the widest possible traces you can.

I do also agree with Ron's sentiments except for caps on the motor size. That's a can of worms I'm not going to get into due to the inductance of the coils of the motor at operating frequency, etc.

Russ
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Old Apr 07, 2012, 02:51 PM
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Quote:
Originally Posted by awrightbrother View Post
Thanks. I am working on a large Lear that has plenty of room in the forward fuselage. I am thinking of using a small PC cooling fan to keep the batteries and ESCs cool. Let's see how that works out. I will do some temp measurements at WOT and will post.
Also remember to block off part of your exit from the fans as that will drive up the load to give you a worst case scenario
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Old Apr 07, 2012, 04:10 PM
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Quote:
Originally Posted by Peacemakr40 View Post
Also remember to block off part of your exit from the fans as that will drive up the load to give you a worst case scenario
Do you mean, block off the EDF fan exit or the PC cooling fan exit?
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Old Apr 07, 2012, 06:01 PM
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Old Apr 07, 2012, 08:13 PM
Capt. Z
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United States, NV, Las Vegas
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Quote:
Originally Posted by Ron101 View Post
I love Andy's build!! in fact so much that I hope to head to vegas for the ace in the hole event to see this beast!
That would be awesome Ron!! Your Hawk, P-51 and Spark would be SWEEET!!! to see. I hope you can make it.
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Old Apr 07, 2012, 09:25 PM
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Russ and Ray, thanks so much for the extremely knowledgeable input. Great data but just as important, great data given in a way that is helpful to the model building community at large.

Hey Russ, do you have any photos / diagrams of your cap banks especially with the several different types of caps including the .1uf ceramic snubber? Trying to visualize how I'd construct it as I've previously just used radial caps in parallel just upstream of the ESC.
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Old Apr 08, 2012, 04:03 PM
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Canada, MB, Winnipeg
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[QUOTE=erh7771;21263704]
Quote:
...Well the FETs are the end result of a problem and you are correct in saying that they should be better but, that costs money and the ESC market is very competitive...[/quote ]

...the quality us good but they are out of spec. There are less quality fets that handle transient power better.

Its also unusual to have this many similar experiences with the device goin wrong...its.not the mcu, regulator or onboard caps that are failing
I think you misunderstood me. When I say "the FETs are the end result of a problem" I mean that there is a problem else where that is causing the FETs to blow. In this case the FETs are being subjected to high voltage spikes that are greater than what the FETs can handle. These high voltage spikes are being created by lengthing the motor cables and not putting caps on the cables to buffer the extra energy. So I agree with you that better spec FETs should be used but, higher rating FETs are more expensive.

Ray
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Old Apr 08, 2012, 04:58 PM
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[QUOTE=Nav_Aids;21272663]
Quote:
Originally Posted by erh7771 View Post

I think you misunderstood me. When I say "the FETs are the end result of a problem" I mean that there is a problem else where that is causing the FETs to blow. In this case the FETs are being subjected to high voltage spikes that are greater than what the FETs can handle. These high voltage spikes are being created by lengthing the motor cables and not putting caps on the cables to buffer the extra energy. So I agree with you that better spec FETs should be used but, higher rating FETs are more expensive.

Ray
Cool, were in the ball park...

I theorize this is the same thing that happened to SUPPO and Hobbywing at one time.They had FETs from factory spec'd at 28 volts but they weren't taking more than 25 volts (for instance) during runs. When higher C rate packs came their FETs started popping like crazy cause the higher c packs could hold such voltages even for a split second. It was found out the tolerances were 10% below voltage and not 10% above voltage.....well good thing, they change the FETs and now I'm able to run 140 amps on 8s for 30usd and I've running them that way for two years with a couple of slight mods for cooling.

Also, it was like maybe 2 out of 10 but you know it only takes one to blow to kill the whole rail

I use heli esc's on my smaller planes and that's how I handle transients with them ...1500 - 2000 watts. but for the larger jets the esc's don't have the slow spool\no slow spool setting the smaller heli escs do or I just don't know how to set them and I run the caps to protect packs more than to protect the esc components.

I've had no issues over the last couple of years running certain escs over spec when it comes to voltages.

My last two CC esc's that blew the leads were very short, less than 6 inches for one of them and I was using less 1200 watts on 50c 10,000mah during testing.
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Old Apr 08, 2012, 06:28 PM
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Quote:
Originally Posted by Eddie P View Post
Russ and Ray, thanks so much for the extremely knowledgeable input. Great data but just as important, great data given in a way that is helpful to the model building community at large.

Hey Russ, do you have any photos / diagrams of your cap banks especially with the several different types of caps including the .1uf ceramic snubber? Trying to visualize how I'd construct it as I've previously just used radial caps in parallel just upstream of the ESC.
I'll put something together for ya so you can see the arrangement and spacing.
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