Ed

OK on Battery Eliminator Circuit, but what does the S that has been added stand for ?

stemo99

Switching, bec switches on and off very quickly to acheive desired voltage output. Linier bec's disapate excess voltage via heat, not efficient. I use only sbec's for my serious models and a few liniers for my knock around foamys.

aeajr

My Feedback: (2)

Both work. They just work by different methods.

Ed

Thank you Folks. Then can I assume from the above statement that the SBEC is more reliable then the BEC ? To take it a step further; is it safe to believe that ESC's with built in SBEC's can be relied on to provide similar performance and reliability, as using a separate receiver and servo battery supply ?

Thank you kindly.

Ed

aeajr

My Feedback: (2)

BEC, battery elimination circuit, is a generic term that applies to all circuits or devices, whether in an ESC or as a separate device that step the voltage to the desired level. You could also call them voltage regulators. They take the power from a battery pack and reduce the voltage to the level desired. For example, an 11.1 V 3S lipo pack gets stepped down to 5V to run your receiver and servos. Most are fixed but some can be set for the desired output voltage.

Whether you do it with a switching or a linear BEC the effect is about the same. I am not aware of any reason to believe that one is more reliable than the other or that an external BEC is in any way better than one integrated into your ESC. The critical issue is the sizing of the BEC to meet the amperage and voltage needs of your equipment.

It is worth noting that linear BECs are more commonly used with lower voltage battery packs. That is because the process of stepping down the voltage from, say 11V to 5 V involves resistance which generates heat. Nothing to be concerned about but that is how it works. So once you get past a 4S lipo or a 12S NiXX pack the step down becomes enough that most manufacturers go to the switching BEC design. This uses the same type of switch on/off process that your ESC uses to regulate the speed of your motor.

There is nothing inherently more or less reliable in either design from a practical point of view. It is just a matter of the most appropriate application for the use case. I would have no hesitation to use a linear BEC on any pack for which it is rated. Nor do I have a big preference for external vs. internal BECs.

One thing to note is that linear BECs are rated for output based on input voltage. So, a linear BEC might be rated for 3 amps output when used on a 2S pack but only 2 amps output when used on a 3S pack. Again, that is related to the resistence method. The higher voltage drop generates more heat so they derate the device for safety. But if you only need 1 amp, who cares?

The biggest issue we face when talking about BECs is that we really don't know what we need in amperage. Do you know how many amps any given servo draws? Did you know that the number goes up when the servo is under load? And, of course, the total amp load goes up if you are moving more than one servo. And a stuck servo's amp draw can go very high.

Typically we evaluate the size of be BEC based on the number of servos, what has worked in other planes or what the MFG recommends.

A Radian Pro, with 6 micro servos and a Spektrum receiver was originally shipped with a BEC rated at 750 mah. Now, most people would tell you that that is not a large enough BEC for 6 micro servos. But there were a LOT of Radian Pros shipped with them and most flew just fine. Later they shifted over to a larger BEC, 1.5 amps I think, to provide a greater margin for high loads.

I hope this was helpful.

Ed

Thanks to Mr. Anderson again, that is the perfect answer. I was just trying to ascertain, that the SBEC rated at 3 A, supplied on my latest ESC, could handle a medium size plane using maybe 3 digital servo's. Two for aileron, and one for elevator on a Telemaster 40.

Thank you.

Ed

ESC link > http://www.hobbyking.com/hobbyking/s...arehouse_.html

aeajr

My Feedback: (2)

Oh, well why didn't you say so. BTW, what are you putting on the rudder? You don't want to fly a Telemaster without the rudder.

Ed

Thank you for your interest. Probably just a conventional analog on rudder, although it could be a digital ? I do have plenty of Spektrum 821's. Should I be concerned about using 4 digitals on that 3 A. SBEC ? The total load would then be 4 Spektrum 821's and a Spektrum AR-7000 receiver.

Ed

Ed

As an old time glow & gas flyer, and a new electric flyer, I am going to have to learn how to do my own Homework. I should have been able to find my servo's and receiver's load specs somewhere, and then added them up, and compared them to that SBEC's capability. I gotta start doing that if I'm gettin into electric, huh ?