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Old Jul 10, 2008, 11:29 AM
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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:
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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 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.

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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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