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Throttle cut off at 50%

Old 04-01-2004, 04:52 PM
  #1  
chuckers
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Default Throttle cut off at 50%

Hiyas,

Anybody feel like solving a mystery today?

I just finished building my first 'real' plane; an Estarter configured as follows:

-----------------
350 motor
Pixie 20P ESC
GWS NiMh 730mah 8.4v (7 cell) battery
Hitec HS55 servos
GWS 6ch receiver
Futaba 6EXA
-----------------

Here's the problem.
As I increase power to the throttle everything is fine until the left stick gets halfway between the full down and full up positions. (By 'halfway" I mean that the stick is at 'click' 12 of 25). On a fully charged battery, at 11 clicks of throttle, the motor will run well for more than 10 minutes, no problem. If I push the stick up 'one more click' (to click 12 of 25) the motor cuts out immediately. The problem is 100% repeatable and very consistent. I see the same behavior with a fully charged battery as I do when I am near the end of my battery life.

I don't have any experience with the 350 motor so I cannot tell if it is running at 'half' power or full power when it cuts off. I suspect that it is NEAR full power ('cause it's pretty loud) but NOT at full power when it cuts of because the LED on the Pixie 20P ESC is still flashing right up until everything cuts off. (I am told that the Pixie 20P LED will remain on constntly while the motor is running at full power.)

I know that my ESC currently has a cutoff voltage of 5.0v, I'm considering changing that to 4.0v, but I don't know if that will help. (This was suggested by the folk at Castle Creations). Do you think that adding power is pulling my fully charged NiMh to less than 5.0v? Will using an excessively low cut off voltage do damage to NiMh batteries? (A cut off voltage of 5.0v equates to 0.71v/cell, and a cut off voltage of 4.0v equates to 0.57v/cell.)

Although the Futaba radio has 'end point adjustments' I don't see anything related to being able to use the full range of the stick. (I tried adjustign the EPA to 120% but didn't see any difference.)

I've cycled the battery 3 times and I'm pleased with the life span. When fully charged it will run the motor for 12-14 minutes on the bench at 'maximum' power (max power being the point just below where it cuts off).

BTW, thanks to all of y'all for lots of good tips about building an Estarter. I've been lurking for a month while I built and today's my first time posting. Here's pic. I finished biulding a week ago but haven't tried to fly yet becasue it's awfully windy lately.

Thanks in advance,
Chuckers
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Old 04-01-2004, 05:29 PM
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Martin V
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Default RE: Throttle cut off at 50%

If you have a voltmeter, you could measure the battery and receiver voltage to see how low it goes just before your motor cuts off.
Also I'm not sure but I think you would want to reduce the end point adjustment until full throddle no longer cuts off the motor.

Martin.
Old 04-01-2004, 05:35 PM
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Martin V
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Default RE: Throttle cut off at 50%

Also, I don't think the EPA should have to be changed to prevent the motor from cutting off. Sounds more like a Battery voltage or ESC problem to me.
Old 04-01-2004, 10:02 PM
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Dopesick
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Default RE: Throttle cut off at 50%

Heya chuckers... Sounds like a battery vs cutoff problem to me, remember I mentioned to you the nimh batteries have a tendency to NEED a few cycles before working correctly.

If your concernaed about it I can loan you a nicd of li-po pack for test purposes.
Old 04-02-2004, 06:37 PM
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chuckers
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Default RE: Throttle cut off at 50%

Thx Dopestick!

Last night I reprogrammed my ESC and got it all working okay. I already have cycled the new NiMh battiery 4x each and am getting pretty decent run times (>15 min).

Toay the wind finally died down enough...got in four short flights at lunch in a baseball diamond near work. It was exciting...if only becasue I had so little open space. There was a mean time of about 4 seconds between dodging one potential disaster to another...LOOK OUT, TREES! whew, LOOK OUT FENCE! whew, LOOK OUT LAMP POST!, etc.

Only damage was knocking the forward gear loose when landing on rough grass.

You going to Baylands this weekend? I think I might try Sat AM again.
Chuckers
Old 04-02-2004, 06:47 PM
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Dopesick
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Default RE: Throttle cut off at 50%

Yup I will be at bayland probably around 9am again, they say the wind will be low until after 10am, then drop after 1pm. So I will probably be there at about 8-9am

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