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Old May 10, 2014, 04:50 PM
Registered User
Joined Feb 2013
82 Posts
BEC or not

Hi There

Looking for any comments on BEC's.

I am building a big EFA with 120mm Fan, designed by http://www.therccustomjets.cz/

Overall it's going to be at least 6 months work to build and a lot of money in the air... (Hope i haven't bitten off more than I can chew!).

I only have an 8 Channel TX, so the electronics Set-up is looking like this....

1. Reciever to Aileron Left
2. Reciever to Aileron Right
3. Reciever to Elevator Left
4. Reciever to Elevator Right
5. Reciever via Y-Lead to Rudder / Nose Wheel Steering Servo
6. Receiver via Y-Lead to YEP 180 Amp ESC / AfterBurner LED's (powered by 3s Pack)
7. Receiver to Door Sequencer
Door Sequencer to Landing Gear Box (powered by 3s Pack)
8. Receiver via Y Lead to Electro magnetic Brake Circuit Board (powered by 3s Pack) (Mixed to down Elevator)

My initial thoughts were....
12S Main Pack
6S Tap to Castle Pro BEC
BEC to Receiver

Q. Would you trust a BEC on your best model or would you go with a separate RX pack? A very knowledgeable chap at my club suggested this was not the best idea...

As you can see above I will already have a 12s Pack and a 3S pack in the model.
I really didn't really want to have another seperate receiver pack as well.

Q. Can you see any other issues with my spec above ?

Thanks for any comments
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Old May 10, 2014, 05:28 PM
Custom Rekitter
tsymonds's Avatar
United States, TX, Killeen
Joined Jun 2011
1,022 Posts
I reference to your question on a BEC here's my opinion. I run a seperate BEC on everything except really small stuff. I use seperate RX packs as well. I use 2s lipos to run all the electronics which I feel is better than using a 3s pack since the extra cell does nothing for longer run time for the RX. It also causes the BEC to work harder to reduce the voltage down to RX level. I run dual RX packs in a 16.5lb 80" P-61 and a seperate one through a Castle Pro in an 11lb BF-109. I feel that the least amount of work a component has to do the better for longevity and reliability and especially so in a setup that has a high amp draw with the heat that goes with it. With electronics heat is the enemy and also if it's run at say 50% of its rated capacity rather than 80-90% the better off it'll be. This is strictly my opinion and your mileage may vary.
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Last edited by tsymonds; May 10, 2014 at 06:02 PM.
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Old May 10, 2014, 05:31 PM
Barefoot Birkinsomething
rcbirk21's Avatar
United States, CA, Hayward
Joined Aug 2004
9,302 Posts
use what you feel comfortable with. i use bec's on everything, as large as a 100cc aerobatic planes. if you setup servos correctly, and make sure wire everything correctly, it can and does work fine. if you are really worried, I wouldnt use the bec pro for that many servos. its a bit more pricey,but check out western robotics bec. they have some other offerings that would work well for you too.
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Old May 10, 2014, 05:44 PM
I eat glue
Canada, NS, Yarmouth
Joined Jul 2006
3,354 Posts
Personally, I would run a separate BEC.
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Old May 11, 2014, 03:33 AM
Registered User
Joined Feb 2013
82 Posts
I have done a wiring Diagram

Any chance you could have a look at this.

Thanks for any suggestions or comments....
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Old May 14, 2014, 03:44 PM
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bradbxyz's Avatar
United States, CA, El Cajon
Joined Jun 2004
107 Posts
I run separate dual LIFE reciever packs in my 100CC equivalent electric planes mostly because I am using HV digital servos. My 65cc sized down to .60 planes are using the CCBEC pro tapped of of one of the 6 cell main packs. I rarely ( castle only) trust a built-in BEC with anything over 3s.

The only downsides to a separate pack is:
1: added weight
2: remembering to charge that sucker
3: remembering to bring it back down to a storage condition when done to avoid puffing.

What you outlined above should work perfectly. My 100CC Decathlon with 5 HV servos burns 225 Mah per 8 minute flight.

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Old May 17, 2014, 04:26 AM
A geriatric flier
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Australia, NSW, Braidwood
Joined Nov 2008
790 Posts
I would agree with bradbxyz. However I use Hitec, Futaba and Align 6v servos (reliable quality servos) and use a 2S LiFe battery direct to the Rx. I and fellow pilots at my club have been doing this for years on planks and helis without logging any servo failures. I have also used Hercules and CC BEC's off 6S (in 12 S setups). Ensure you power the BEC with the neg wire connected to the neg side of the ESC.
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