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Screwy battery pack causes twitching?

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Old 09-24-2003, 01:41 AM
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RS2K
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Default Screwy battery pack causes twitching?

I have a strange problem. I'm about to fly my new 3D Freedom with an RCS 1.40 and while setting up the radio I've noticed that my servos twitch a bit. I've tried both a PCM and a PPM receiver as well as two different transmitters (a 9Z and a Super 7) with the exact same result. When I move any servo to the point of full deflection back and forth I get a little tiny twitch. If I keep on it the twitching gets worse and worse.... And uhhh, while typing this and playing with my TX, my airplane just a did a sort of "Death Pose" all the servos just went to more than full deflection. I am running 6 volts and my battery is just about dead when this "Death Pose" happened. Could voltage drop have something to do with this?


I have ruled out "servos, TX, RX, and antennae routing"
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Old 09-24-2003, 06:13 PM
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Default RE: Servos twitch on PCM!?

Some twitching is normal in 6 volt system when it's fully charged (a good reason not to use them) The twitch you're talking about at full deflecting does sound like a voltage drop problem. Check and recheck all your wireing and make sure you're using high enough gage. When in doubt use 3 gages higher than you 'should' if you can aford the extra weight, which isn't significant.
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Old 09-24-2003, 07:42 PM
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Default RE: Servos twitch on PCM!?

Umm this is really weird. I tried cycling my battery pack over night and my dymond super turbo WILL NOT discharge this pack. It will charge it but not discharge it. I tried taking off a cell and it did the same thing at 4.8v... I might be wrong, but I think 4.8 volt packs work better with lower gauge wire because of the way the servos recieves command from the RX. I then took my 4.8v .0000000032 GAh battery off my raptor and that one works A-OK. There is obviously something very screwy with my battery pack... Any idea what it could be?
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Old 09-25-2003, 01:25 AM
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Default RE: Screwy battery pack causes twitching?

Lower gage wire will never improve how an RC setup functions. There is absolutly no reason not to use the largest wire (within reason) your setup will allow. You get more efficiant power transfer because resistance is lower, and consiquently you have lower voltage drop. The only way to be sure what's wrong with your pack is to take it apart and test each individual cell. If your charger is not letting you discharge through it I'd say send that pack into recylcing bin.
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Old 09-25-2003, 01:37 AM
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Default RE: Screwy battery pack causes twitching?

Won't I be limited by the servo gage? Would it be better just to replace the whole servo wire instead of adding an extension?

Where is a good spot to get low cost high gage wire? I'm not too fond about spending $10 a piece for servo extensions.
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Old 09-26-2003, 12:15 AM
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Default RE: Screwy battery pack causes twitching?

Pick the gage you want and find a local electrical contractor or supplier in your area, there should be at least one or two around that will sell you three conductor wire of any gage you want. All you have to do is open up your local Yellow pages and look under Electrical, a couple phone calls will save you a buck load of money if you need a bunch of extensions or just want to be able to do your own electrical work. The only problem is connectors, you should be able to find a place that sells crimp style standard 3 pin header's they're used EXTENSIVLY in computers and virtually all other kinds of electronics products and they'll cost you 1/5th the price of a Futaba J connector. It is a little more work than most people would want to do though. That's half the fun to me.
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Old 09-26-2003, 09:13 AM
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Default RE: Screwy battery pack causes twitching?

That sounds like the ticket. I'll try that, thanks for the info!
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Old 09-27-2003, 02:34 AM
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Default RE: Screwy battery pack causes twitching?

Is there any metal on metal contact in the linkage? That would cause titches too.
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Old 09-27-2003, 02:54 PM
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Default RE: Screwy battery pack causes twitching?

None at all. Every link is a ball linked and external, the only thing that runs inside the fuse are the servo wires and the throttle extension which is carbon fiber. The antennae runs up from the the rear of the cockpit the the tail and is not touching anything else at all. The ignition is at least 12 inches from anything else that has to do with control, but I havn't tried running with 6 volts while the engine was running yet..

I've been using 4.8 volts and plan on doing so untll I redo all my servo wires to a heavier gage. Then I plan on moving up to 6 volts.
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