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Battery need

Old 06-03-2019, 06:32 AM
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Default Battery need

Hello, I am putting together a 20cc plane in which I installed 5 servos hitec HS-5645MG 12 kg at 6v and a receiver spektrum AR620 with a ubc of 6 v output for receiver. My question is: what would be the necessary capacity of the battery to supply the current demand of the 5 servos.

I put a lipo battery 2s 1500mah. But the servos fail to stop working apparently for lack of current. is offline  
Old 06-03-2019, 10:29 AM
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The LiPo and UBEC combo should be fine - as long as the UBEC is 5A or more.. 2S LiPo is between 6.6 (discharged lowest level) and 8.4V (full charged).

But Personally ... I would have used a 2S LiFe battery and then you do not need the UBEC.

I suspect you have other problems unless one or more servos are plugged in wrong ... or UBEC is faulty ...

Have you metered the voltage at the Receiver ?

Last point ... I assume this is a 20cc gasoline engine with ignition ? If so - how are you powering the CDi ? Not a good idea to power the CDi and Receiver via same UBEC.
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Old 06-03-2019, 06:14 PM
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My rule is simple, if the aircraft is large enough to carry a battery pack for receiver and servo power, then it gets one.

I worked on a plane all winter, for a Winter Build Challenge. About 20+ pilots and 25+ planes were there Saturday for the maiden flights. I had done a lot of testing of my Neutrino flying wing. For some dumb reason, I put retracts with full closing doors on it. More work than I thought. Not much space so I used a UBEC with my opto ESC.

Passed a full safety check, then I dropped off the charge in my batteries. Next time I plugged in the battery, the system went crazy. Every thing going all possible directions, servos, retracts and doors (out of phase of course)

Even though my switching type UBEC was rated for use with at least a 6S battery pack and a 5 amp output, and I was only running a 4S pack, it started sending out a very dirty 6v to the RC system in the plane, so much so that it burned out the control board in the nose gear retract

I had the drop out, because the nose gear was stuck in the up position. I will find some place to put a flight batter in that plane but it is a very tight fit.
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