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Power Systems Talk about motors, ESC speed controllers, gear drives, propellers, power system simulators and all power system related topics

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Old 02-21-2008, 06:13 PM   #1
f4ucorsair
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Default Pulsating Motor

I have a Hobbico ElectriStar Select, it flew just fine for several months, but now the motor pulsates at full throttle with fully charged batteries (2, 7 Cell 3000 mAH NiMH, or 2, 2S 4350 mAH LiPo), ESC is 45A Dual Battery Input, Motor Hobbico C-42. There is not enough power to take off or if it starts to pulsate in the air it looses power quickly and I have to land. Replaced the ESC but no change.
Any Ideas?
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Old 02-21-2008, 06:18 PM   #2
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Do you mean you have power surges (on and off)?

If so that is an indicator your batteries may not be up to task.
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Old 02-21-2008, 08:14 PM   #3
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Default Pulsating Motor

Not on and off, but pulsating RPM's
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Old 02-21-2008, 08:16 PM   #4
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That is your LVC (low voltage cutoff) turning power to yoru motor off indicating that it is below the cutoff voltage.

Do you have a watt meter?

And did you change any settings on yoru ESC (like the voltage cutoff)?
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Old 02-21-2008, 08:25 PM   #5
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Default Pulsating Motor

No Watt Meter
ESC automatically sets the voltage cutoff
Charge batteries with Hobbico Accu-Cycle Elite
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Old 02-21-2008, 10:51 PM   #6
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Try a smaller prop and see if that "helps" without the meter we are simply guessing!
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Old 02-21-2008, 11:28 PM   #7
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I had the same problem with a inexpensive e bay outrunner on a 3s lipo system. I found if I moved the throttle back to about 3/4 stick the engine ran fine at max rpms. Sadly pilot error occured before I had my watt meter. Just a thought.
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Old 02-22-2008, 07:19 PM   #8
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Thank you, I'll look into these suggestions
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Old 03-02-2008, 03:54 PM   #9
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I use the Electrify SS-35 esc on a ducted fan, and it indeed pulses (changes RPM up and down) when the low voltage cutoff is met.

If you are getting this problem and can't even take off, then it does sound like your batteries are old or need to be cycled a few times (fast charge & fast discharge). Try and cycle your batteries 3 or 4 times to see if they come back to life.

You might want to also connect a voltmeter and check your battery voltage; Nicad or NiMh should be 1.2v per cell at least, and typically around 1.4v fresh off the charger. So, a 7-cell pack should be at least 8.4v.

If you need some new batteries, this place looks like it has some good prices:

http://www.all-battery.com/index.asp...OD&ProdID=1713

Richard
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Old 03-03-2008, 03:06 PM   #10
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Default Pulsating Motor

Thanks Richard,
I just cycled both NiMH batteries, I'll try them out today. I also run two 7.4V, 3000mAH Li-Polys in this airplane and the same thing happens.
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Old 03-19-2008, 04:39 PM   #11
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Default Pulsating Motor

This problem is getting to me.
I recycled, discharged batteries (batteries are good) still have the same problem (motor RPM's pulsate at full throttle with loss of power).
I put the batteries in another airplane and had no problems.
Put batteries in from another airplane and had the problem.
What else could be wrong?
The motor and ESC are new.
The odd thing is when the airplane was new all worked fine, there have been no changes to the setup.
Any ideas, anybody?
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Old 03-21-2008, 07:47 PM   #12
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Originally Posted by f4ucorsair View Post
This problem is getting to me.
I recycled, discharged batteries (batteries are good) still have the same problem (motor RPM's pulsate at full throttle with loss of power).
I put the batteries in another airplane and had no problems.
Put batteries in from another airplane and had the problem.
What else could be wrong?
The motor and ESC are new.
The odd thing is when the airplane was new all worked fine, there have been no changes to the setup.
Any ideas, anybody?

At what rate do you charge the batteries? Try charging the NiMH at 4amps or more. I know the batteries will heat up more, but you should get more punch for the initial requirement of take-off. (short term solution)
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Old 03-25-2008, 04:25 AM   #13
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Check the connectors from battery to ESC. A bad connection seems to make mine do that too. I discovered by accident that jiggling the wires while it was pulsating brought full power. Then I tracked down the bad connection.

John
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Old 03-25-2008, 04:33 AM   #14
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Hi F4ucorsair If all the wiring is good and tight, and the lipos/ batteries are good, you might have a bad motor, the windings are opening up inside the motor under a electrical load, I had that happen to me, try another motor, if that works, your old motor is no good, it has a flying open in the windings under a electrical load, hope that helps, Chellie

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Old 03-31-2008, 08:46 PM   #15
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Default Pulsating Motor

Thanks for all your responses so far.
The motor and ESC are new.
I will look into the wiring next, ie: connectors and such, maybe I'll come up with something there.
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Old 04-09-2008, 03:06 PM   #16
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I had a similar issue that may shed some light on your pulsating rpm...I was using a rimfire 35-30-1450 with the SS-45 ESC and a 10 cell NiMH in a great planes siren...I smoked the motor in about 5 seconds after successfully setting up the brake on the ESC. My motor smoked visibly with the associated smell and on close inspection of the coils I noted two of the coils were visibly deformed and discolored. Afterwards the motor seems to misfire / scream with a raspy voice type of noise with the pulsating rpm drops. Occasionally the motor will not turn but the ESC is sending the pulses and it just squeels without turning the prop (sounds like a stripped gear.

hope this helps...doug
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