Ubec and inbuilt ubecs

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Ubec and inbuilt ubecs

Postby jet760 » Sun Aug 22, 2010 1:09 pm

Hi I have a electric plane ( Eflight Ultra stick 25e) that I am running with a 60amp turnigy plush speedy with a inbuilt switching BEC. I had a problem today where it had appered to loss power to the Rx for a short time, causing the plane to crash, (I think it was a bad connection from the plug into the Rx) being a spektrum Rx the short power outage meant it rebooted when power came back but the rebind was to slow and being only 10m of the ground the isn't much time for the reboot to happen. I am guessing it was a power outage as the Rx was flashing when I went and picked up the bits, and all servos where moveing normaly. I know that if this happened to my Frsky, the reboot would of been instant and would of showed up as a glitch. But anyway I ahve a Ubec which people say you should install in larger Speedies. If i run the speedy and a separate Ubec off the same battery and plug them both into the Rx do I have to disconnect one of the + or - lines off either one so its not getting power from both "becs" to the Rx or because they would be effectedly suppling the same voltage or close to the same to Rx would it be ok. I was thinking this would be like a fail safe, that if one bec failed the Rx is still getting power from the other Bec.
Hope someone can help with this.
Regards David
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Re: Ubec and inbuilt ubecs

Postby RCModelReviews » Sun Aug 22, 2010 11:45 pm

I've been doing a little testing and I've found that few (in fact none) of the ESC BECs I've tested so far will actually deliver the performance they claim (and certainly not once the ESC itself starts getting warm).

I'd recommend using a UBEC that appears grossly over-rated for any such applications -- just to be safe.
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Re: Ubec and inbuilt ubecs

Postby jeffie8696 » Mon Aug 23, 2010 4:38 am

But can he use the UBEC together with his ESC or will he have to cut the wire from his ESC?
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Re: Ubec and inbuilt ubecs

Postby crampy » Mon Aug 23, 2010 6:20 am

It's as simple as removing one wire from the ESC plug. No problems
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Re: Ubec and inbuilt ubecs

Postby jet760 » Mon Aug 23, 2010 6:59 am

I was hoping to keep them both as a type of fail safe. if one fails there still is power to the Rx.
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Re: Ubec and inbuilt ubecs

Postby RCModelReviews » Mon Aug 23, 2010 8:11 am

If you try to use them both then you run the risk of damaging one or both of them.

Best to remove the positive wire from the lead to the one you don't want to use.
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Re: Ubec and inbuilt ubecs

Postby mvvs35 » Mon Aug 23, 2010 6:33 pm

Hi I have a question about the UBEC. it is recommended that it be linear or switching, for example: Dual Sky VR8L or Castle (http://www.castlecreations.com/products/ccbec.html).

Thanks!

Greetings!
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Re: Ubec and inbuilt ubecs

Postby RCModelReviews » Mon Aug 23, 2010 7:06 pm

There are pro's and cons to both.

Switching UBECs are far more efficient and that means they generate less heat and are often smaller than the equivalent linear unit. However, they can create some RF noise which might have an effect on some receivers (especially the older non-2.4 units). They often do a better job of providing a constant output if the battery voltage drops to a level very close to the required output level but will stop suddenly when the voltage falls too low.

Linear UBECs are often larger and heavier and they also run hotter but produce no RF noise. They also tend to keep delivering some voltage right down to the point where the battery is almost dead.

In most cases, hi-current UBECs tend to be switching types.
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Re: Ubec and inbuilt ubecs

Postby ergocentric » Tue Aug 24, 2010 1:24 am

RCModelReviews wrote:If you try to use them both then you run the risk of damaging one or both of them.

Best to remove the positive wire from the lead to the one you don't want to use.


You wouldn't consider diodes to protect them from each other?
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Re: Ubec and inbuilt ubecs

Postby RCModelReviews » Tue Aug 24, 2010 1:41 am

If you do that then one of them will still end up doing almost all the work because it will have a slightly higher voltage than the other -- and you're introducing two new points of failure (the diodes).

KISS rules! Just use a decent UBEC in the first place and you're probably a lot better off.
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