BEC is nothing but a battery circuit is an electronic circuit, It is especially designed to deliver electrical power from one to other circuitry without using any battery.

 

BEC is nothing but a battery circuit is an electronic circuit, It is especially designed to deliver electrical power from one to other circuitry without using any battery.

Huh? "BEC" has become a broad term in RC and is not an electronically universal term. It was first enlisted in semi-early RC cars (in the 80's). It was made so that the typical 7.2-8.4V power-train battery pack could also supply the power to the receiver/servo's that could not typically exceed 5-6V.

In early systems, the voltage regulation was inside the receiver, and you were able to plug a full voltage battery line into the receiver (And these receivers were LARGE!). After the electronic speed controllers (ESC's) became mainstream, the BEC regulation was commonly built into the "ESC". RC cars are very standardized, so unless you need crazy high BEC amperage (Typically in rock crawlers with crazy high power steering servo's), your ESC will provide it.

Planes vary so much in servo requirements dependent on size, style of aircraft, it has become very commonplace to use an external dedicated BEC (Also because reliability is way more of an issue in the air obviously). I know what the OP is trying to do, but it is not overly logical to attempt at a beginners electronics skill level due to the ramifications of the outcome if it does not work as planned.

 

Good day my friend,

I agree with you in one thing that aircraft must be reliable before airborning. So everything I do is going under heavy loading and testing before it gets to work. I have quiet extensive skills in electronics, but more to that, deep skills in equipment testing. Therefore my prototype is under heavy loading this days. So far performs without any sign of trouble

You are right also in another situation, you asked me for the plane type. It is Edge 540, equipped with DLE 20cc. I got 3 standart S3004 servos, and 3 high torque servos. The maximum current consumption, is <7A ( on digital meter, I only see 2.5A, when I artificially load the control surfaces) at full loading. I have been testing my BEC to 15 A continuous, it has now built in cooler.

Its weight is about 105qr. So, this type of aircraft, I will probably use normal 1.2vx5 NiCd batteries, with 1800mAh capacity. Which is more than enough for 0.5 hour flight time. I will save this project for my larger aircraft.

The flying field is just empty desert, so the chance of hitting some civilian is zero, except my own car.

However, you got true points

 

Here is the video on you tube, from my first hook ups.

http://www.youtube.com/watch?v=TLR6cCjmzA0&feature=youtu.be

Gents, would like to clarify one thing:

I got laptop battery, stripped it and retieved Li-ions. it says on battery 11.1v, 56Wh. There are 6 batteries inside, 3 series connection , and these triplet is paralleled. So one cell turns out to be 56/11.1/2=2500mAh?

Each LI-Ion cell is then 3.7v/2500mAh, right? Its late midnight here, and I'm tired....

 

Yes.
......

 

Right. If we take that all onboard electronics consume 5A @ 6v, it makes 30W. And the current drawn from the battery will be 30/11.1V=2.7A. This is at 100% efficiency.

What efficiency should I expect from this linear BEC? 85?-90? worst case, @ 80% efficiency it will be 3.4A. therefore should be able to fly around 40 mins non-stop (which is never the case...)

I will measure output current from the battery @11.1v, and the after the BEC @6v. Will try to come up with realistic value for efficiency

 

"""The comparison of linear BEC and switch-mode BEC: When using a lithium battery pack more than 3S, a switch-mode BEC has much higher efficiency than linear BEC.  For a traditional linear BEC, For example, a 4S lithium battery pack has a typical voltage of 14.8V, in order to let BEC output 5V/1A, the current flow into the BEC is at least 1A, so the power on BEC is 14.8V* 1A=14.8W. But the useful output power is only 5V*1A=5W, so the efficiency of the linear mode BEC is just 5W/14.8W=33.8%, the redundant power 14.8W-5W=9.8W changes to heat, which makes the BEC very hot.  For a switch-mode BEC in the above case, in order to let BEC output 5V/1A, the current flow into BEC is only 0.38A (actual test data), so the power on BEC is 14.8V* 0.38A =5.6W, and the efficiency of BEC is 5W/5.6W=89.3%"""""


I took this from the manual of one UBEC on the e-net...what are they trying to sell here??

Pin=Pout+Pheat

so 9.8W is burnt as heat? don't believe this...

 

Sad but true. Linear supplies suck at efficiency. That's why I've been trying to talk you into a 97% efficient switcher that is less than half the size.

 

I'd also only consider running 2S lithium, I'd forget the NiCd/NiMh stuff altogether, too much weight for a plane IMO. 2S will stress your BEC less than 3S/4S as it isn't going to have to deal with dissipating as much voltage. Any pics of your pane? My favorite is my 3DHS 48" Edge, but it is electric. Have considered going gas recently (I will never do glow engines again!). Any reason against spending $22 on the Castle 10A BEC? They work great, are compact, and USB programmable. I have one in every vehicle in this picture (Except the buggy, only half of one of my crawlers is pictured, but it has one):

 

Here is the picture of my Edge, and my heli.

I;ve ordered LM3150, it will take 2-3 weeks to get to my country.

Regarding purchasing CC BEC, it mentions about 5mph air flow requirement, for 7A continuous. Therefore I'm a bit hesitating to believe its power. Cheap stuff is not always reliable at higher power requirements. You must be doing some music just like me also?