ESC & BEC What's the Deal? - WattFlyer RC Electric Flight Forums - Discuss radio control eflight

Power Systems Talk about motors, ESC speed controllers, gear drives, propellers, power system simulators and all power system related topics

ESC & BEC What's the Deal?

Old 04-25-2007, 05:58 AM
  #1  
Murocflyer
WAA-08 Pilot #1
Thread Starter
 
Murocflyer's Avatar
 
Join Date: Mar 2007
Location: Edwards AFB, CA
Posts: 7,044
Default ESC & BEC What's the Deal?

I've always wondered about this.

I have never flown a plane with more than four servos and never really gave it much thought. But now I am thinking about using six servos, or maybe seven and have read about needing a BEC along with an ESC because that many servos will be pulling too many amps and overheat the ESC.

Can anyone provide some real world insight on this? What have you experienced relative to using more than 4 servos and how do you have your system setup and with what brands of ESCs and BECs are you using?

Is all this a myth or is there any truth to that.

Thanks for the info,

Frank
Murocflyer is offline  
Old 04-25-2007, 08:43 AM
  #2  
rea59
BEEP..Bleep..BEEP
 
rea59's Avatar
 
Join Date: Jul 2006
Location: Midway Kentucky
Posts: 1,228
Default

ESC = Electronic Speed Control
BEC = Battery Eliminator Circuit

Key word being Eliminator

An ESC usually has a BEC built in. This allows you to use the motor battery to also power the servos. This usually provides a max of 5 volts.

More servos can reduce your flight time and yes overheat your ESC. Also your cutoff voltage on the ESC could render your servos inoperable if you have too many.

The plane I'm currently building uses 12 servos so the ESC's I bought were without BEC. The motor batteries will not be able to provide any power to the servos. For the servos I'm using a 6 volt 2100mah receiver battery. The 6V is to increase the torque of the servos for the large control surfaces. (standard is 4.8v)

Hope this helps some, others may have more info.
rea59 is offline  
Old 04-25-2007, 08:45 PM
  #3  
Murocflyer
WAA-08 Pilot #1
Thread Starter
 
Murocflyer's Avatar
 
Join Date: Mar 2007
Location: Edwards AFB, CA
Posts: 7,044
Default

Thanks Ray. Your project sounds very interesting. Where is the build thread?

So, is everyone using a BEC when flying with over 4 servos? If not, what are you using?

Thanks,

Frank
Murocflyer is offline  
Old 04-25-2007, 09:58 PM
  #4  
jdetray
Member
 
Join Date: Aug 2005
Posts: 330
Default

The BEC in a speed controller is a voltage regulator that reduces your main battery voltage to a level that is safe for your receiver and servos, usually 5V. In the process, waste heat is produced.

The more current the BEC is asked to provide (to power the servos), the more heat is generated. Also, the greater the difference between the main battery voltage and the BEC output (5V), the more heat is produced. On the snall circuit board that makes up an ESC, it can be difficult to dissipate all that heat.

That's why built-in BECs may be rated for 4 servos on a 2S lipo, but only 3 servos on a 3S lipo, and perhaps only 2 servos on a 4S lipo. I am not aware of a speed controller with a built-in BEC that can handle more than 4 servos.

There are two solutions for handling more than 4 servos. One is to add a separate BEC for the receiver and servos and disable the BEC in the ESC (or use an ESC without a BEC). You'll still be using just one battery, but the separate BEC will be able to source enough current for all your servos.

The second solution as mentioned by Ray is to use a second battery for the receiver and servos. In this case, you don't use any BEC at all. The downside is that your plane must carry two batteries, which may be heavier than one battery plus a separate BEC. It's more common to see the two-battery solution in larger planes, where the extra weight is not so critical.

- Jeff
jdetray is offline  
Old 04-25-2007, 10:10 PM
  #5  
Grasshopper
Some Assembly Required
 
Grasshopper's Avatar
 
Join Date: Feb 2006
Location: Nashville, TN
Posts: 12,070
Default

Hi Frank,

I'm running 7 servos in my P-38. I used a 3 amp BEC and disconnected one of the wires to the ESC. I'm pulling power for the BEC off the two 3S 2100 15C lipos paralleled together so I didn't need a seperate battery. Here's the BEC I used.

https://st86.startlogic.com/~rcepowe...bd8a1fd88f25a4
Grasshopper is offline  
Old 04-25-2007, 10:28 PM
  #6  
rea59
BEEP..Bleep..BEEP
 
rea59's Avatar
 
Join Date: Jul 2006
Location: Midway Kentucky
Posts: 1,228
Default

Originally Posted by Murocflyer View Post
Thanks Ray. Your project sounds very interesting. Where is the build thread?


Frank
Here's the thread. F4U Corsair

In my case it's a very large plane and will be using a total of 3 batteries.

Motor = 2 x 10s Lipo (may use 10s2P) By the time Iv'e finished this build there may be better technology batteries out there.

Servos = 1 X 6V Nicad
rea59 is offline  
Old 04-26-2007, 04:27 AM
  #7  
Murocflyer
WAA-08 Pilot #1
Thread Starter
 
Murocflyer's Avatar
 
Join Date: Mar 2007
Location: Edwards AFB, CA
Posts: 7,044
Default

Originally Posted by jdetray View Post

That's why built-in BECs may be rated for 4 servos on a 2S lipo, but only 3 servos on a 3S lipo, and perhaps only 2 servos on a 4S lipo. I am not aware of a speed controller with a built-in BEC that can handle more than 4 servos.


- Jeff
Jeff thanks for the info. I was afraid I was going to hear that. I don't know why they ESCs aren't made to carry more load?

Can you recommend an ESC without the built-in BEC? Or do you normally disable the regular ESCs and add a BEC.

Thanks,

Frank
Murocflyer is offline  
Old 04-26-2007, 04:31 AM
  #8  
Murocflyer
WAA-08 Pilot #1
Thread Starter
 
Murocflyer's Avatar
 
Join Date: Mar 2007
Location: Edwards AFB, CA
Posts: 7,044
Default

Originally Posted by Grasshopper View Post
Hi Frank,

I'm running 7 servos in my P-38. I used a 3 amp BEC and disconnected one of the wires to the ESC. I'm pulling power for the BEC off the two 3S 2100 15C lipos paralleled together so I didn't need a seperate battery. Here's the BEC I used.

https://st86.startlogic.com/~rcepowe...bd8a1fd88f25a4
Tom,

You link is not working, but no worries. You mentioned disconnecting one of the wires. Can you please explain that in a little more detail? A picture would be a plus.

Thanks,

Frank
Murocflyer is offline  
Old 04-26-2007, 04:39 AM
  #9  
Grasshopper
Some Assembly Required
 
Grasshopper's Avatar
 
Join Date: Feb 2006
Location: Nashville, TN
Posts: 12,070
Default

That's weird. When I click on the link in my post it doesn't go but when I click on it in your quote above it does. Here it is again. See if it works now. If not, it's at www.rcepower.com and look in the ESCs for a 3 amp BEC.

https://st86.startlogic.com/~rcepowe...bd8a1fd88f25a4

Here's a link to my P-38 thread that discusses disconnecting one of the wires to the ESC. Look at post #9.

http://www.wattflyer.com/forums/showthread.php?t=12165

Let me know if you need more info.
Grasshopper is offline  
Old 04-26-2007, 05:02 AM
  #10  
jdetray
Member
 
Join Date: Aug 2005
Posts: 330
Default

Frank -

I am no expert on brands or models of BECs, but I can offer some observations.

One vendor whose BEC products seem to be popular is Dimension Engineering. Another is the Ultimate BEC from Kool Flight Systems. I've never used these products, but their reputation seems to be good.

One way to disable the BEC of any ESC is to disconnect the power wire in the small 3-conductor cable that goes from the ESC to the receiver. This is the middle of the three wires, usually red in color.

Among the ESCs that are available without a BEC are the Jeti "Opto" line. I'm sure there are others.

- Jeff

Last edited by jdetray; 04-26-2007 at 05:27 AM.
jdetray is offline  
Old 04-26-2007, 06:52 AM
  #11  
rea59
BEEP..Bleep..BEEP
 
rea59's Avatar
 
Join Date: Jul 2006
Location: Midway Kentucky
Posts: 1,228
Default

Mine is the Castle Creations Phoenix HV-110 High Voltage ESC

Castle Creations

Last edited by rea59; 04-26-2007 at 07:29 AM.
rea59 is offline  
Old 04-26-2007, 05:12 PM
  #12  
Murocflyer
WAA-08 Pilot #1
Thread Starter
 
Murocflyer's Avatar
 
Join Date: Mar 2007
Location: Edwards AFB, CA
Posts: 7,044
Default

Thanks for all the info Fellas. I need to make a shopping list on what ESC and BEC to buy. Laser Arts will be coming out with its Switchback Sport 150 soon and I'm dreaming of flaps and ailerons and maybe retracts.

I just gotta figure out what to buy now.

Thanks again for the help/info and I'll be checking your links here shortly.

Frank
Murocflyer is offline  
Old 04-26-2007, 07:49 PM
  #13  
rea59
BEEP..Bleep..BEEP
 
rea59's Avatar
 
Join Date: Jul 2006
Location: Midway Kentucky
Posts: 1,228
Default

Big Planes are great!!

Of course your wallet will be empty long before your list is complete.
rea59 is offline  
Old 04-26-2007, 08:49 PM
  #14  
Franny
Stupid Gravity!
 
Franny's Avatar
 
Join Date: Oct 2005
Location: Arvada, Colorado (just moved...)
Posts: 504
Default

Hey Tom?

Any word on how your RCEPower BEC works? Any problems? It looks like it is a linear regulator and the Demention Engineering is a switching type. Does yours get very warm?

Thanks,

Franny
Franny is offline  
Old 04-26-2007, 09:02 PM
  #15  
Grasshopper
Some Assembly Required
 
Grasshopper's Avatar
 
Join Date: Feb 2006
Location: Nashville, TN
Posts: 12,070
Default

Hi Franny,

So far it has worked perfect. I really can't tell you how warm it gets because it's under the wing in the center pod of the P-38 and I don't ever take it apart.
Grasshopper is offline  
Old 04-27-2007, 03:34 AM
  #16  
Murocflyer
WAA-08 Pilot #1
Thread Starter
 
Murocflyer's Avatar
 
Join Date: Mar 2007
Location: Edwards AFB, CA
Posts: 7,044
Default

Originally Posted by rea59 View Post
Big Planes are great!!

Of course your wallet will be empty long before your list is complete.

They are sweet and yours is looking wonderful. Oh, don't even mention money. well maybe not , but

Frank
Murocflyer is offline  
Old 04-27-2007, 07:20 AM
  #17  
Bmiller
EDF Member
 
Bmiller's Avatar
 
Join Date: Dec 2005
Posts: 793
Default

I was looking at my new hobbylobby catalog and noticed the new jeti spin ESCs have switching BECs for use with more than 3S lipos (4S to 8S depending on the ESC amp rating)and higher than usual servo counts.
example: Spin44 2-6 lipoly 5.5V BEC 5A max 8 servos.
Interesting stuff!
Bruce
btw I am NOT affiliated with anything or anybody!
Bmiller is offline  
Old 04-27-2007, 03:12 PM
  #18  
rcers
Super Contributor
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,314
Default

I am not aware of a speed controller with a built-in BEC that can handle more than 4 servos.
As indicated above - they do make a few but they are $$$.

Jeti Spin and Hyperion both make switching BEC's in their ESC's...

http://media.hyperion.hk/dn/titan/titan.htm

Also don't forget the good old stanby of a 4cell NiCad pack!

Mike
rcers is offline  
Old 04-27-2007, 04:11 PM
  #19  
Franny
Stupid Gravity!
 
Franny's Avatar
 
Join Date: Oct 2005
Location: Arvada, Colorado (just moved...)
Posts: 504
Default

I saw on Horizon's site that Castle is coming out with a 10A 6S/25V input BEC for $~20 => http://www.horizonhobby.com/Products...rodID=CSECCBEC

Looks like late April. Don't know if it is linear or switching...

It sure would be nice to have some kind of on-board monitor for the power... Just a simple voltage and current check with maybe a super bright red flashing LED on the bottom of the airplane to signal a problem. I guess I'm a bit parinoid now after crashing and burning up a $150 Lipo and almost my airplane due to (*I think*) overloading the onboard BEC of a CC 60A ESC with four cells.

Franny
Franny is offline  
Old 04-27-2007, 04:49 PM
  #20  
Hitch
Member
 
Hitch's Avatar
 
Join Date: Aug 2006
Location: Fairfax, VA
Posts: 94
Default

I just bought this one for my GWS CargoTrans (running it with 5-6 servos):
http://www.dimensionengineering.com/ParkBEC6v.htm

Its $19, 6v out, and connects to the battery leads on your speed controller so no need for an extra battery. The feature that sold me though, was that you plug the receiver lead of your ESC directly into this BEC, then plug the BEC into your receiver - no need to disable the power wire on the ESC.

Just solder leads, then plug BEC into ESC.
Hitch is offline  
Old 04-27-2007, 04:57 PM
  #21  
Murocflyer
WAA-08 Pilot #1
Thread Starter
 
Murocflyer's Avatar
 
Join Date: Mar 2007
Location: Edwards AFB, CA
Posts: 7,044
Default

Originally Posted by Hitch View Post
I just bought this one for my GWS CargoTrans (running it with 5-6 servos):
http://www.dimensionengineering.com/ParkBEC6v.htm

Its $19, 6v out, and connects to the battery leads on your speed controller so no need for an extra battery. The feature that sold me though, was that you plug the receiver lead of your ESC directly into this BEC, then plug the BEC into your receiver - no need to disable the power wire on the ESC.

Just solder leads, then plug BEC into ESC.
Hey now this is pretty cool stuff. How is it working out for you?

Frank
Murocflyer is offline  
Old 04-27-2007, 05:03 PM
  #22  
Franny
Stupid Gravity!
 
Franny's Avatar
 
Join Date: Oct 2005
Location: Arvada, Colorado (just moved...)
Posts: 504
Default

Hey, that is cool! Switching too!

f
Franny is offline  
Old 04-27-2007, 05:18 PM
  #23  
Hitch
Member
 
Hitch's Avatar
 
Join Date: Aug 2006
Location: Fairfax, VA
Posts: 94
Default

Not flying yet Just bought it a few days ago after looking for one for a while. I have it installed, but now need to finish the airplane. The key for me was 6v, taps into my existing battery, and not having to modify my ESC.

Originally Posted by Franny View Post
It sure would be nice to have some kind of on-board monitor for the power... Just a simple voltage and current check with maybe a super bright red flashing LED on the bottom of the airplane to signal a problem. I guess I'm a bit paranoid now after crashing and burning up a $150 Lipo and almost my airplane due to (*I think*) overloading the onboard BEC of a CC 60A ESC with four cells.
You might want to consider installing an EagleTree logger. http://www.eagletreesystems.com/MicroPower/micro.htm
Ill be buying one for my helicopter shortly. If you look at all the extensions you can add onto it (the REALLY cool ones coming out mid next month) then it could solve your problem. Granted it wont alert you in real time, but you can do some light flights and look at the graphs afterwards to see what is going on. It will show you Volts, amps, watts, and MaH used out of the box. Then you can add on temp sensors, rpm sensors, and soon airspeed and elevation, as well as servo loggers to track how many amps a servo is drawing!! http://www.helifreak.com/viewtopic.php?t=26681 has some examples of graphs for peoples' Trex 600s.
Hitch is offline  
Old 04-27-2007, 05:32 PM
  #24  
Murocflyer
WAA-08 Pilot #1
Thread Starter
 
Murocflyer's Avatar
 
Join Date: Mar 2007
Location: Edwards AFB, CA
Posts: 7,044
Default

Originally Posted by Hitch View Post
Not flying yet Just bought it a few days ago after looking for one for a while. I have it installed, but now need to finish the airplane. The key for me was 6v, taps into my existing battery, and not having to modify my ESC.
Would you mind posting some pics when you get the chance on your setup with this BEC?

Thanks,

Frank
Murocflyer is offline  
Old 04-27-2007, 05:37 PM
  #25  
Hitch
Member
 
Hitch's Avatar
 
Join Date: Aug 2006
Location: Fairfax, VA
Posts: 94
Default

Yup. At work now, but Ill try and get them up either late tonight, or early tomorrow.
Hitch is offline  

Quick Reply: ESC & BEC What's the Deal?


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.

Page generated in 0.10585 seconds with 13 queries