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Old Feb 19, 2004, 06:51 PM
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How do you know when a motor is bad??

I have a new gws 350 motor with c gear box. Right now I'm using a 1080 gws prop, pixie 20p esc and two 1200 mah etec lipolys running in parallel.

When I ran the setup with one lipoly the esc would cut out as soon as I put the throttle up past half way. That was on the 6 volt and 5 volt cutoff. I bought another lipoly to run in parallel so that way I would have 2400mah and 18amp to run the motor with. When I throttled up to max it runs for about a second or two and than the esc cuts it off again.

I don't have a multimeter yet (I have one on order) But would you say that the motor is bad causing to high of an amp draw which is causing the esc to detect a low voltage and shut off the motor??
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Old Feb 19, 2004, 06:56 PM
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I'd say the motor is fine if it spins up. Check that your battery is charged up, and then check you battery to ESC connections (when you get your multimeter ) .


Andy
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Old Feb 19, 2004, 07:04 PM
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ok, I'll give that a shot. Maybe the cold has something to do with it. It was only 40f out. Could that have anything to do with it??
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Old Feb 20, 2004, 04:53 AM
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Re: How do you know when a motor is bad??

Quote:
Originally posted by jacksonjrs
I have a new gws 350 motor with c gear box. Right now I'm using a 1080 gws prop, pixie 20p esc and two 1200 mah etec lipolys running in parallel.

When I ran the setup with one lipoly the esc would cut out as soon as I put the throttle up past half way. That was on the 6 volt and 5 volt cutoff. I bought another lipoly to run in parallel so that way I would have 2400mah and 18amp to run the motor with. When I throttled up to max it runs for about a second or two and than the esc cuts it off again.

I don't have a multimeter yet (I have one on order) But would you say that the motor is bad causing to high of an amp draw which is causing the esc to detect a low voltage and shut off the motor??
Have I missed something obvious, you say you ran it on just two cells in PARALLEL? That is only 4.2v at best.

You need to put the two cells in series....? :-(

Or have I misunderstood what is going on here?
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Old Feb 20, 2004, 06:01 AM
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Sorry about the confusion it wasn't two cells, it was two battery packs. Each pack is the 2s2p 1200mah 7.4 volt.
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Old Feb 20, 2004, 06:57 AM
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Right. Things get clearer. First of all, on that voltage on a 10x8 you are likly to be trying to drag the best part o 12A out of the motor. I'd say that was too much. Frst off I'd say a 9x7 was the better match.

Secondly, its not clear whether the cells are 1200mA/h, or the packs.

If you hace two packs each of 2s2p E-tech 1200;s then you shold be able to pull 15A a pack, but yu eem to suggest that each pack is only 1200mA/h, so that makes each cell 600mA/h?

E-etch are 700 and 1200, so not sure where that leaves us....

IF you are using just two e-tech 1200's per pack in series, then its not surprising that dragging 12A or so out of them flips the cutoff. However two in parallel, assuming proper connections, should work as long as the motor holds up...which won't be long by my reckoning

See the datasheet for that motor and box, cells and prop here...

http://www.aircraft-world.com/prod_d...em/eps350c.htm

8x6 to 9x7 recommended, or 10x4.7, or at most 10x6.

So thats the first thing to fix.

Then you should be able to run on 2s20 e-tech 12200 no problenms. However thigs still seem a little out of whack, so you may want to at least borrow a voltmeter and see of you are gtting around 6.5 volts under load across the ESC input.

Maybe you are using too thin wire or something or a bad type of battery connector, that is losing power.

You SHOULD be able to run the 350C on 2s2p packs of 1200' etechs no problem.

The oly other thing that migh tcause very high currents is if the gearbox or motor is binding.
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Old Feb 20, 2004, 10:03 AM
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Same issue with a 300C

Had the same issue with a GWS 300C-C, Pixie 7p with 2s Kokam 1500 HD. Either a 10X4.7 or 9.7 would engage the cutoff at 3/4 throttle with a fresh charge. Programmed the Pixie to the soft cutoff mode and it works fine now, but I prefer the hard cutoff.

I still dont understand why the motor would drag the pack down to under 3volts/cell, the batteries are new (less than 10 charges on it) and the motor was broken in.

Only thing that I can think of that might be a problem is the JST connectors. I attached them to the Pixie with nice solder joints, so hopefully that isnt the problem. Could be the leads are too long?

Anyone know the best way to check the power from the batteries under load with a standard multimeter? Im not an electronics expert, and dont have the money currently for a Whattmeter.

Thanks....

TB
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Old Feb 20, 2004, 11:45 AM
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JST connectors will not handle that current. If they are not the problem now, they will be soon. You need to replace them. Deans polarized 2 or 3 pin connectors are better suited for that application.

That motor/prop will probably draw 6 to 7 amps. Thats pretty close to the Pixie limit

I think most standard multimeters have a current function. Does yours ?
If it does, then read the current. Lets say it reads 7.5 amps. Then, Power (watts) = current times voltage, so, if your battery reads 7.5 volts times 7.5 amps =59.75 watts
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Old Feb 20, 2004, 01:41 PM
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how much current will a 300c motor draw? would a 8.4 730mah nimh be good enough? if not, what motor would be?
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Old Feb 20, 2004, 05:09 PM
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Well, I set up the meter when I got home and checked the voltage using the meter. Cutoff happened exactly at 7V when on the 6V hard cutoff setting.

Im going to replace all the JST connectors with Deans mini directly to the Pixie leads. Hopefully the better connectors and shorter leads will correct the problem.

TB
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