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Old Sep 13, 2014, 03:44 AM
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Back up power in case of BEC burn out.

Hi all,

Last year I built a 1m pylon racer type plane and had lots of fun. However, due to poor cooling, the motor overheated and caused the ESC to burn out, with lots of pretty smoke.

This also led to the plane crashing as the BEC went up with the ESC and the RX then had no power.

I remember someone at the time saying one could use a small 1s pluged into a spare RX Chanel to provide emergency power to keep the RX and servos functioning to get you back to the ground instead of a lockout! They also said that as its only 1s it would receive a trickle charge from the BEC while the main batt was plugged in and so be ready to go as and when needed.

So, my question is, will the above work assuming the RX is capable of working at such low power levels? It seems a nice and above all LITE way of a bit of safety.

Chees

Tom
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Old Sep 13, 2014, 06:09 AM
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That would most likely set the 1s Lipo on fire as it be getting charged to whatever voltage the BEC was running at(5 to 6 volts). It might even make the ESC go pop as the current going to the Lipo could be more than the BEC can deal with.

The only real safe way of doing it is to run a separate RX supply and remove the red wire from the ESC or fit a opto between the ESC and RX.

Assuming you're not running massive power on a model like that why not just give things the required amount of cooling and run as normal? My Wot 4 with 1kW and 5 servos has been running BEC for years now.

Steve
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Old Sep 13, 2014, 04:57 PM
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Cheers Steve.

I'm not worried about the cooling of the motor. My last one failed because I didn't give it fresh air and its a mistake I won't be making again. But, that's not the only reason a BEC could fail and it's a shame to lose an airframe due to the RX and servos having no power.

I am just trying to find a way of a light weight battery back up. It seemed a reasonable way of achieving the aim with out a full blown dedicated RX batt.

These models are at there best if kept light and they are always at a premium for space.

Maybe another idea will materialise.
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Old Sep 13, 2014, 06:15 PM
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How about an external BEC?

Juan
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Old Sep 14, 2014, 01:51 PM
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Look into the scorpion backup guard
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Old Mar 02, 2015, 11:10 PM
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This circuit would also work. It is made in the U.S.A.

http://lasercuttingbyjohn.com/produc...p-bec-circuit/
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