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Wire Lenght????

Old 03-20-2011, 02:57 AM
  #1  
Big Johnny
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Default Wire Lenght????

Hey Folks, Just a quick question. I building a twin. Is it better to lengthen the battery wires or the motor wires on the esc. I read one time the correct way but I have forgotten. The Batteries have to be in the fuselage, but I can place the esc's in the wing or fuselage.
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Old 03-20-2011, 03:13 AM
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rcers
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Motor side.

How long you talking?

Mike
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Old 03-20-2011, 03:17 AM
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gramps2361
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Myself I use a seperate wire from the battery to the esc. I had 2 twins that had one battery in the fuse I had long seperate wire from the battery to the esc. My P-38 has 2 batteries in the pods and a heck of a lot of wire to run them in parallel. Never had a problem so far with this set up.
Hope this helps a little.
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Old 03-20-2011, 03:45 AM
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rcers
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Gramps long battery wires can cause major grief. Voltage ripple is the issue, makes that esc work really hard. The caps are there to help with that even on short battery runs.

If you are talking about short extensions on the battery side you will likely get away with it, but more than 6-8" I rarely do.

Mike
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Old 03-20-2011, 04:27 AM
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gramps2361
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Great just what I needed to read. From the battery on the P-38 the goes from the battery to the center of the wing to meet for a parallel connection then back to the ESC. That is about 13 to 14 inches of wire for one side total. I had one member tell me that is how he did it and didn't have a problem.
Hope he was not wrong, what is you feelings on this hate to repeat advice if this is not a good setup. More over I would really hate to lose this plane.
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Old 03-20-2011, 04:35 AM
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By the way Johnny I didn't mean to hijack your thread. this point is good that it came up though.
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Old 03-20-2011, 04:39 AM
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My AC-47 is configured with two batteries in the nose that parallel into one line that goes to a splitter at the wing. Separate lines go out through the wing to each of the nacelles, where the controllers are right next to the motors.

Works like a charm (even when I use old batteries )



Total wire length from battery to motor, about 14" (and thats x2)

Last edited by Nitro Blast; 03-20-2011 at 04:58 AM.
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Old 03-20-2011, 05:07 AM
  #8  
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Ya that is about the same Lent I had on the twin star and the twin Mini tele master I had. Weak batteries that was funny.
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Old 03-20-2011, 10:34 AM
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Larry3215
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I get a kick out of these long wire threads. There are always one or two or sometimes several people who chime in with examples of how they are getting away with long battery leads and having "No problems".

Come to think of it, virtually ALL threads involving "rules" seem to go the same way, from batteries, to flying, to building etc etc

Obviously its not a hard rule that results in instant death and destruction every time you go over 6.354" on your battery leads.

Like most "rules", there are exceptions and there are people who "get away with it" and are proud to tell you all about it.

However, keep in mind that every single esc mfg in the world - with ONE exception - tells you to keep the battery leads as short as possible or you will shorten the life of or destroy your esc.

The single exception is a company - I think in Germany - that makes a true sign wave esc. Ive forgotten their name at the moment. Those esc's work very differently than ours do. Plus they start at several hundred dollars for the cheapest ones
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Old 03-20-2011, 10:42 AM
  #10  
CHELLIE
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I keep forgetting that info too motor length wire or battery length wire that needs to be kept short, Thank you Larry, this time i saved it to Word Pad So i dont forget Take care, Chellie
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Old 03-20-2011, 10:49 AM
  #11  
Larry3215
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By the way - if you ARE going to run long battery leads, here are a few things you can do to make it easier on the controller and reduce the risk and maybe keep your plane in the air longer. Sometimes there really is no other good option.

1) Use over sized, quality, higher C rated batteries than you would normally use. Batteries that cant handle the peak loads easily are the major cause of ripple. Higher internal resistance increases the ripple. Most battery packs are grossly over rated so keep that in mind too. So use more battery than you would normally think you need to handle the current.

2)Use controllers that are over sized in terms of peak voltage and peak current. If your running a 3S setup that pulls 40 amps peak, use a 6S controller rated for 80 amps.

3)Add extra Low ESR capacitors of the same size and voltage rating as the ones already on your controllers. Add them as close as possible to the controller end of the wires.

4)Use larger gauge wire between the batteries and controllers.

5)Be extra careful with connectors and solder joints to be sure you have the lowest possible resistance at all points along the line.

6)Braid the battery leads but not to the extent that it requires extra wire.

7)Use slightly larger motors and prop down a bit rather than smaller motors that are over propped.

8)Dont use the internal BEC's on the controllers.
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Old 03-20-2011, 01:59 PM
  #12  
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DARN IT LARRY.... i have to have the perfect length and just checked all my planes...........they are all 6.355...........

now i gotta go and resolder them all .001 less in length....lol....

seriously though,thats great advice Larry,theres a lot of threads i read lately on the subject due to a deans arming switch i put in the battery circuit in the hog. i figure the 100 amp esc will cover the extra inch's of heavy gauge wire used.[motor calls for 80amp esc]

i always search threads on topics and couldn't find a combo thread that included info on both adding length and the deans plugs.

lastly ,i think i need to remember the battery wire lengths include the leads on the esc,the leads on the battery and then what ever we add in between. just a pic of the length of wires installed in the hog,i hope not to have to add any extra componets due to resistance.
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Old 03-20-2011, 02:17 PM
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rcers
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Originally Posted by Larry3215 View Post
8)Dont use the internal BEC's on the controllers.
That is another for sure. I watch three twin crashes over the years two in one day. All were traced to built in BEC failures when run in parallel. (Another raging debate!). While I have seen more crashes than this all three of these were one thing - BEC failures. Two of them were with Castle controllers that say no issue with parallel BECs.

I always use a separate BEC with twins - zero exceptions. Just cheap insurance.

My buddy has a Liberator with LONG battery lead runs - over 3 feet. He commonly has ESC issues, motors starting at different times and ESC's going wonky. I told him switch to using long motors leads and his issues will go away.

And just to show Larry is right (there are exceptions to every "rule") I have one plane I extended the battery leads about 12" on and flew that beast for many many flights (300 plus) running an 10amp Phoenix ESC. It was running at 10-11amps too. Guess what - zero issues. So fate is a funny, fickle beast.

Mike

Last edited by rcers; 03-20-2011 at 02:49 PM.
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Old 03-20-2011, 02:19 PM
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gramps2361
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Well I think my plane gets taken apart again, and just run the one battery one motor for each side time the flights to see what is drawn down from the batteries.
With my wire leads from the battery to were they meet the extra solder joints and back sounds like I would just be asking for trouble down the road.
I would rather fix this than risk a ESC failure with a crash we Will leave it to dumb thumbs rather than a component failure do to user being too stubborn to make a easy fix .

Thanks everyone for answering Johnnies question and getting me squared away also. That's a 2 for one deal.
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Old 03-20-2011, 02:24 PM
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Mike I do that anytime I run 4 or more servos and all the twins had a ubec in them.
geez I thought I was ready for a maiden flight soon, but this is a quick fix instead of a possible trash back.
Johnny had to give you a click on the thank's your question helped me.
thanks
John
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Old 03-21-2011, 12:34 AM
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Nitro Blast
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Although I failed to mention it, I also use a UBEC with twins. It was told to me as essential also, and for me it was just convenient as my ESC's are Opto's without BEC.



Sheesh... I've done and broken another rule. You are looking at 18" of wire, NOT counting what goes inside the wing, out to the ESC's.
Spooky is 2+ years old, and more flights than I can count without an electronic device.
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Old 03-21-2011, 12:49 AM
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Big Johnny
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Thanks for all the information. I have a Dynam DC-C (A.K.A. Skybus), it blew the capacitors in one of the esc's. I'm rewiring it with the esc's closer to the batteries, 50 amp esc's & bec. I'm only drawing 25 amps, so I think I'm safe with the esc's
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Old 03-29-2011, 03:03 PM
  #18  
r_kopka
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Originally Posted by Big Johnny View Post
it blew the capacitors in one of the esc's.
That's the lesser problem. I had one model (some years ago, when that knowledge was not widespread) that ate 3(!) ESCs before I added capacitors and didn't have problems anymore. Not just the capacitors, the power part went up in flames.

And it didn't happen immediately. One ESC was tested and burnt the next time. One was tested several times and burnt when trying to start. The third one lasted one flight and died the next one.

RK
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Old 03-29-2011, 03:38 PM
  #19  
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From all that I have read from the people that MAKE esc's, on a "park flyer" size airplane, it really doesn't matter which wires you make longer. If you are talking about a large plane where you are adding a foot or two of wire...then always increase the motor side wires.

On my P38, I increased the battery side wires by about 10". Not a big increase and I was able to gain fantastic cooling by mounting the esc's in the cowls. I figure the gain in cooling was worth the slight lose in power by the long battery wires.

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