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Old Jul 10, 2008, 11:29 AM
oct2633 is offline
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BESC vs. UBEC

Can someone help me on the definition/function of these two items? Are they interchangeable (same thing), or separate electronic devices with different uses?
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Old Jul 10, 2008, 01:19 PM
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Well, I'll take a stab at this and hopefully someone will pop in and correct whatever errors I make with my explanation.

Some, but not all, modern ESC's have a battery eliminator circuit built into them. There are two basic types of these BEC's - linear and switched. The linear BEC's tend not to like higher voltage or higher amp draw from the servos and are usually only good if you're planning to run 4 servos up to the voltage that a 3 cell Lipo can provide. I believe this has to do with the amount of waste heat that a linear BEC produces when stepping voltage down to the 6V that the RX wants to see.

Switched BEC's seem to be rated to drive more servos at higher input voltages (4 cell Lipo and up) and can handle the amp draw of more servos (manufacturers have different specs on this). Newer ESC designs seem to have Switched BEC's rather than Linear BEC's

Finally there's the UBEC. This is a separate component that can be installed in the event that the BEC in the ESC is not rated for the application you're using it in. For example if you were using a Castle Phoenix 35A ESC with 6 servos and powering the motor/ESC/RX with a 4 cell Lipo you'd want to buy and install a UBEC as the Phoenix's BEC's are only good up to 3 cell Lipos and rated for 4 servos. Various UBEC's install similarily - they all tap the power lines coming from the battery to the ESC in some form. The ESC may or may not pass through them.

For more info on UBEC's see DimensionEngineering's site. Good info there:

http://www.dimensionengineering.com/
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Old Jul 10, 2008, 01:35 PM
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To answer the question oct actually asked, BESC usually stands for Brushless Electronic Speed Control....it drives a brushless motor and is not really in any way related to a UBEC.

A UBEC is a standalone Battery Elimination Circuit which allows the main power battery to produce a lower voltage to drive the receiver and servos.

Some confusion may arise because many ESCs (brushless or not) have a built-in battery elimination circuit or BEC as ronin4740 says.

Steve
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Old Jul 10, 2008, 03:43 PM
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UBEC is a bandnameof switching BEC.

SBEC is both a brand name and a generic term for switching BEC.

SBECS generate interference, but a fairly constant amount of heat independent of load and supply voltage.

Linear BECS generate no interference, but a lot of heat, which gets worse with load and higher supply voltages.

Linear BECS are very cheap and come built into most ESCS.
Switching BECS are more expensive, and are usually sold separately, but more are being built into ESCS.

Both will shut down and crash your model if you exceed the ratings, but linear BECS will do it at surpsringly small loads, due to heat.
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Old May 10, 2016, 03:24 AM
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now i am total confused here...
so dumb this down for me. BEC means you dont have to run a seperate battery pack to run the reciever.
opto means you HAVE TO RUN a battery pack...
UBEC means you dont have to run a battery pack ( because you are running a 2 cell or 3 cell MAX battery??
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Old May 10, 2016, 05:55 AM
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Old old thread but nothing much has changed in the last 8 years .

ESC with BEC built in means the ESC can supply power from the main battery to the receiver/servos so no separate battery needed.

OPTO ESC doesn't supply power to the receiver/servos so you either need a separate battery pack OR a separate BEC (sometimes called a UBEC). Nothing to do with 2 or 3 cell maximum though, most modern BECs can handle much higher voltages.

Steve
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Old May 10, 2016, 08:33 AM
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Quote:
Originally Posted by cougar33 View Post
now i am total confused here...
so dumb this down for me. BEC means you dont have to run a seperate battery pack to run the reciever.
opto means you HAVE TO RUN a battery pack...
UBEC means you dont have to run a battery pack ( because you are running a 2 cell or 3 cell MAX battery??
There are two kinds of BEC, internal to the ESC or external to the ESC.

There used to be a external BEC that was sold as the "UBEC" meaning Universal BEC. The term UBEC has become a generic term that is used by some to refer to external BECs of any make or brand.

An external BEC can be connected to the same battery as the ESC to get more current than you can get from the ESC's internal BEC. The different connection types and schemes are well explained on Castle Creation's BEC page:

http://www.castlecreations.com/products/ccbec.html

Click on the "CC BEC Wiring Diagram" to see an image of the connections, there are other images there also.

Jack
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