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Old Jul 06, 2015, 06:42 PM
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Question
BEC still feeding receiver

Hi. I've spend some time searching the forum but all references I found are of the normal BEC disabling procedure.

Thing is this: I have an old Phoenix-45 ESC that I'm using with 12 NiMh and an Ultimate BEC, so I disconnected the red wire from the servo cable as instructed to disable the internal BEC.

I noticed that on battery connection there was significant sparking. Since the ESC is not supposed to arm immediately I assumed it was the U-BEC drawing some current so I added a switch to the connection between the main pack and the U-BEC.

Sparks still appear with the switch off and to my surprise, the receiver is being powered!!! If I disconnect the servo connector from the ESC to the receiver, it doesn't power up immediately but until I enable the switch, as expected.

How is it possible that the already disabled BEC is powering my receiver?
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Old Jul 06, 2015, 07:17 PM
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The spark is normal. It’s caused by the capacitors being charges. The higher the voltage the larger the spark. That’s normal on all electric powered airplanes.

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Old Jul 07, 2015, 10:30 AM
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That is correct... What you are seeing is the caps being charged.
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Old Jul 07, 2015, 11:57 AM
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Okay, so it seems I wasn't actually solving a problem in the first place, but just adding more complexity with no reason hehe... Thanks for the feedback!

And I actually found out why the receiver is being powered even with the U-BEC switched off: I added the switch to the U-BEC negative lead... it happens that it still has the positive hot all the time and it's being grounded through the receiver, then through the ESC servo ground wire then to the battery...

So: should I remove the switch altogether? No real benefit?
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Old Jul 08, 2015, 10:06 AM
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Yes - remove the switch from the ground. What you may be doing by breaking the ground is creating a "floating" ground that may damage other components.
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Old Jul 08, 2015, 10:09 AM
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Got it! Thanks a lot!
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