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Two batteries into an RX8R rx?

Discussion about Tx, Rx, Servo's, Batteries, Chargers, and all the other things we like to talk about..
Moderator: VinceC
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RobbieB
Posts: 547
Joined: 07 Mar 2015, 22:22
Location: North West

Re: Two batteries into an RX8R rx?

Post by RobbieB »

Shame about that Peter although I'm not surprised. The low mass and consequent associated low inertia of the rotors in our little servos would mean a rapid rise to full speed and a consequent very brief initial load current.

I think the relevant point here is, that start up load is likely to be relatively high and will, of course impose itself every time the motor (every motor in the installation) starts up - or tries to start up holding control surfaces in position during flight regardless of control inputs. It was the sum of these start-up loads that has really interested me particularly in large servo installations.

I remember reading a report a long time ago, not long after the first 2.4 sets were available from an electronics guy who installed a data logger in one of his models and to his horror discovered an enormous number of receiver dropouts during the flight, most corresponding to spikes in brief voltage drops. Originally he thought is was a flakey receiver but subsequent tests displayed the same behaviour on all his receivers. All that said, he never at any time experienced anything untoward with the models behaviour in the air - interesting.

I think you can probably have your thread back now Rog.......
Barry_Cole

Re: Two batteries into an RX8R rx?

Post by Barry_Cole »

Looking at the spec on those 6 amp diodes, they have a peak forward current of 400 Amp, albit for a VERY short period of time. I have been using similar 6 Amp diodes on my tugs for quite a few years with no problems.

The old S+M battery backers that used to be available used 2 amp diodes, so I think the 6 amp ones will be just the job.

BC
Jolly Roger
Posts: 573
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Two batteries into an RX8R rx?

Post by Jolly Roger »

Thanks gents. This is WAY more interesting than the original topic! :D

I admit I’d never given much thought to start-up currents. I think they are modest in this model, with just half a dozen analogue HS85s.
Elliot Howells
Posts: 333
Joined: 18 Mar 2015, 08:18
Location: West Wales
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Re: Two batteries into an RX8R rx?

Post by Elliot Howells »

Rog, let's have a detailed account of what/ how you do it ;)

Ell x
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RobbieB
Posts: 547
Joined: 07 Mar 2015, 22:22
Location: North West

Re: Two batteries into an RX8R rx?

Post by RobbieB »

There you go, I knew it was there somewhere.

Very simple.
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