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Old Mar 27, 2012, 07:03 PM
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BEC & aux power can it safely be done?

I have a B25 I am using a 2-60a eflite esc....with BEC. I am using a seperate battery for rx power. Can I also activate the bec to provide power to the rx through the T channel, giving me two power sources to rx providing redundancy in the case of one power source failing?

Thanks!
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Old Mar 27, 2012, 10:59 PM
This is NOT a TOY?
C_Watkins's Avatar
United States, GA, Atlanta
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Quote:
Originally Posted by Show 871 View Post
I have a B25 I am using a 2-60a eflite esc....with BEC. I am using a seperate battery for rx power. Can I also activate the bec to provide power to the rx through the T channel, giving me two power sources to rx providing redundancy in the case of one power source failing?

Thanks!
Not safely/reliably, without designing a circuit to allow you to do that.
If you're really wanting the redundancy, just add another battery if the extra weight isn't an issue.
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Old Mar 28, 2012, 04:41 AM
An itch?. Scratch build.
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It is possible to do all sorts of configurations regarding power supplies, but they need some serious thought.

Basically servos can be supplied with power, +ive and -ive from one source, and the signal link from another, ~signal and -ive. The negatives -ive, needs commoning across the different power supplies.

This can be handy if using say retracts that may one day hang up/jam and keep the servo stalled trying to move them.
I prefer my retract servo(s), to have their own supply, just in case. It could be done with any servo, or group of servos, but will need some additional wiring.
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Old Mar 29, 2012, 09:26 AM
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I just look at it the bec is 6v to the rx. the battery is 6v. people plug 2 6v batteries into a rx all the time including myself for redundant power, why would the bec be different than a 6v battery providing power through the T channel?

Thanks!
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Old Mar 29, 2012, 10:12 AM
This is NOT a TOY?
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Odds are that a lot of the time it wouldn't be a problem. Depends on the circuitry design and component specs of the BEC.
Can't say for sure, in any case, without a lot more work than is feasible... or by simply making your plane the guinea pig

Sure, two batteries work great.
Paralleling in a BEC is not like just adding another battery, though.
Depending on the design, you could potentially damage the BEC.
If that happens, and it happens to fail 'shorted' rather than 'open' then you've had a bad day.
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Old Mar 29, 2012, 03:11 PM
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Quote:
Originally Posted by Show 871 View Post
I just look at it the bec is 6v to the rx. the battery is 6v. people plug 2 6v batteries into a rx all the time including myself for redundant power, why would the bec be different than a 6v battery providing power through the T channel?

Thanks!
When you plug two 6v (or any volts) batteries in parallel, they instantaneously pass a current between each other to get themselves to exactly the same voltage. Provided they're both at approximately the same state of charge, the amount of current is not enough to cause any problems.

But with a battery and BEC supply, the BEC is probably regulated quite well to give a constant 6v, but the battery voltage may be well over 6v initially, and could go well below 6v during use. So, in practice you might damage the BEC when you apply battery voltage to it's output (depending on what electronic protection it has built-in) and, more importantly, as your flight progresses you'll possibly get to the point where the BEC is actually doing all the work because the battery voltage has gone down to 6v.

There are electronic devices that can instantly switch from one power source to another if the first one fails, but they're generally used only for large models.
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