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Old Aug 13, 2012, 08:34 PM
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Joined Aug 2012
3 Posts
ESC, BEC values

The spec sheet for the ESC I am using lists the bec values as 5v/2a. Does this mean that the bec should shut down power delivered to the motor at 5 volts? My power source is a 3s, 2100 maH, Lipo, 25C. The esc shuts down motor power with battery voltage at just over 9 volts. Is this normal? Battery charges and balances OK.
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Old Aug 13, 2012, 08:40 PM
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dmcquinn's Avatar
Chesterfield (St.Louis) MO
Joined Jan 2004
320 Posts
The "5V/2A" means that while in operation, the BEC supplies a 5 volt power to the receiver up to 2 Amps of current. If the receiver and servos draw more than 2A of power, then the BEC is not suitable for this application. Two Amps is a lot of current - plenty for a sport plane under 5 pounds.

The ESC will quit supplying current to the motor at 9 V for a 3-cell LiPo. This is pretty typical as you don't want to discharge the LiPO to less than 3 V per cell.
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Old Aug 13, 2012, 09:57 PM
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USA, MO, Ballwin
Joined Mar 2010
634 Posts
The BEC capability is fine for most airplanes unless you are pushing more that four servos with additional demands such as 3-D.

As a reference point, my P-47 with flaps and gear never drops the voltage below 4.9 no matter what you do. This is a stock ESC w/BEC. So if you fly "normal" aircraft "normally" you wont' need a separate pack.

I did this test aggresively and never saw an issue.
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Old Aug 14, 2012, 02:48 AM
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Staffs, UK
Joined Nov 2003
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Bit of confusion there I think. The BEC is the part of the device that supplies power to the receiver and servos. It has nothing to do with shutting the motor down when the battery voltage gets low. That's a function of the ESC itself called LVC (Low Voltage Cutoff).

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