What Is A Battery Eliminator Circuit?

- James Whomsley | FliteTest

What is a BEC? What is a UBEC? What on earth is an SBEC? This article will uncover the mysteries of the Battery Eliminator Circuit.

A battery eliminator circuit is a voltage regulator. It is designed to drop a big voltage down to a smaller voltage. As modern RC airplanes use high voltage batteries, it allows you to run your receiver, servos and other accessories from your main battery without using a separate lower voltage one. There are lots of types, so let's jump right in.

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An ESC with a built-in BEC

Do ESCs have them?

Yes! Most Electronic Speed Controllers have in-built Battery eliminator circuits. This means you really don't have to worry about much; all you have to do is plug your BEC lead into the receiver and you'll have the required power fed to it. Usually, this is 5 volts. Sometimes, though, you might still require a dedicated BEC for higher powered models.

Are there different types of BECs?

Yes, there are quite a few.

BEC - Linear Battery Eliminator Circuit

SBEC - Switching Battery Eliminator Circuit

UBEC - Universal Battery Eliminator Circuit

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Let's look into this in more detail.

(Linear) BEC

A simple battery eliminator circuit does what it says on the tin. It steps down power, but in doing this it's actually quite wasteful. This is because, when you get rid of power like this, you turn your energy into heat. So, although a simple BEC is easy to use, it is inefficient and expends useful power.

In addition to this, BECs can't really be used with bigger batteries with higher voltages. This is because the higher voltage would make the BEC far too hot and it would fail (electronics don't like heat). They are, therefore, only usable in the small stuff.

(Switching) SBEC

An SBEC is little more complex than the humble BEC, but it means that you can often power high powered models through one. It works by using a switching, alternating current to step down your battery voltage to a safe 5v for your RC gear. Virtually no power wasted by the SBEC and you can still run large amounts of power through it. A capacitor and coil smooth out the average of the switching current and allow the RC gear to run on a consistent voltage.

(Universal) UBEC

A universal battery eliminator circuit, for all intents and purposes, is the same thing as an SBEC. It uses a switching regulator to control the voltage to your vital electronics. Confusingly, both terms (UBEC and SBEC) are used as some brands one or the other. Increasingly, UBEC is being used as the standard term.

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An ESC with a built-in SBEC

So which should I use?

It really depends on what power system you're thinking of using. For most applications, you can get away with using a simple ESC which handles everything for you. You can find ESCs like this in all of our Power Packs on the FT Store. Occasionally, if you need a lot more power and want to run batteries that are over 4 cells, you might want to consider using a UBEC/SBEC ESC or a seperate UBEC.

Original article at FliteTest, here.

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