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Aug 21, 2012, 01:38 AM
Registered User
Discussion

speed control bec or external bec


I am using a 60A speed control rated for 3 to 6 s lipos. i am running 2 9gram servos for ail, 2 9g servos for flaps, and 2 9g servos for the rudder and elevator. will my speed control support all this on a 3s setup made in series to be 6s; I am not sure if i should use a separate reciever battery, could someone please help?
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Aug 21, 2012, 04:19 AM
Frequent Flyer
whitecrest's Avatar
What are the specs for your speed control's BEC?
Aug 21, 2012, 05:55 PM
Registered User
on 5s lipo it will run 2 standard micro servos in linear mode, switch mode it will do up to 4 micro servos on 6s. 80A burst current,
Aug 21, 2012, 05:58 PM
Registered User
Quote:
Originally Posted by pwg212
I am using a 60A speed control rated for 3 to 6 s lipos. i am running 2 9gram servos for ail, 2 9g servos for flaps, and 2 9g servos for the rudder and elevator. will my speed control support all this on a 3s setup made in series to be 6s; I am not sure if i should use a separate reciever battery, could someone please help?
I am going to say that it will probably not do it. That is a lot of voltage that will be bled off as heat. Lean on the side of caution and install a UBEC. Most esc's will work on up to 3s with about 4 servos. It probably has a 2.5-3A BEC built in. Question is... Is it linear or switching? If it is linear, I would definitely switch it out, if it is a switching type, I would still prolly do it. I have a similar set up and my Rx voltage was getting dangerously low at times. CC BEC and problem solved
Aug 22, 2012, 01:00 AM
Registered User
R Zielinski's Avatar
Quote:
Originally Posted by pwg212
on 5s lipo it will run 2 standard micro servos in linear mode, switch mode it will do up to 4 micro servos on 6s. 80A burst current,
Sounds like you answered your question. Even if the specs say it will work, I would not risk 6 servos on any ESC BEC, switch mode or not. I believe the servo capacity goes down as the battery voltage goes up, so a 6S setup is the riskiest of all. Stepping down the voltage causes heat in the BEC, which can then cause the ESC to reach thermal safety shut down. Digital servos and the ubiquitous "tower pro" 9gm servos are notorious power hogs. Move all 6 at once and you've got voltage drop trouble. Granted the flaps may not move much, but any binding will create amp draw from the "stationary" servo. Even riskier with 2.4 Ghz receivers, some of which are prone to low voltage brown outs and momentary loss control during re-arming. Why risk it? Get a separate BEC.
Last edited by R Zielinski; Aug 22, 2012 at 01:07 AM. Reason: typo
Aug 22, 2012, 03:16 AM
Registered User
Quote:
Originally Posted by pwg212
switch mode it will do up to 4 micro servos on 6s.
And you have 6 servos on a 6S battery. 6 is more than 4 so there's your answer.

Whether you use a separate RX battery or a standalone BEC is up to you but that ESC definitely won't hack it.

Steve
Aug 22, 2012, 01:48 PM
Registered User
E-Challenged's Avatar
"UBEC" was a product name for an add-on switch mode BEC no longer made. You just want an add-on switch mode BEC (SBEC) rated for your application. Go to Dimension Engineering's website to read FAQ's and installation guides and capacities of their SBEC's. Good folks, will answer e-mail questions. DE has lots of other gadgets of interest to RC'ers and experimenters.
Aug 22, 2012, 02:16 PM
See you in Valhalla
7oneWo1f's Avatar
Quote:
Originally Posted by pwg212
I am using a 60A speed control rated for 3 to 6 s lipos. i am running 2 9gram servos for ail, 2 9g servos for flaps, and 2 9g servos for the rudder and elevator. will my speed control support all this on a 3s setup made in series to be 6s; I am not sure if i should use a separate reciever battery, could someone please help?
What is the speed control? Some already have switch mode BECs. Also need to know the current, whether you plan to deploy your flaps at full speed as a type of airbrake (not good in my opinion) or just use them to improve lift at slow speed (better approach).


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