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Old Jan 16, 2005, 01:46 PM
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Rockland County, New York, United States
Joined Sep 2004
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AXI 2208/34 - 9x3.8 APC SF - 3s1p 830 mah

I tried using this setup and i lose power after 2 minutes of flying, ive tried to use a bunch of other setups and I always lose power. I follow the charts on flyingmodels, and I still lose power. Im not understanding why. I built a mini 3dx. - i used 3 mm depron, 3 Futaba S3108 micro servos, foam safe CA, AXI 2208/34 - 830 mah 3s1p LiPo. Ive always had trouble with getting power for a prolonged period of time on any electric plane. However if i go to the field, everyone else is getting 10+ minutes of vertical 3d flying while I only ever get 2 minutes. Im really not understanding, what it is I am doing wrong. NEVER got more then a 5 minute flight.

Any ideas on an axi 2208/34 - prop and battery recomendations?
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Old Jan 16, 2005, 05:00 PM
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hornet_dave's Avatar
USA, IA, Cedar Rapids
Joined May 2003
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What speed control are you using? It could be a low voltage cutoff issue. What is the battery voltage before and after the five minute flight?
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Old Jan 16, 2005, 06:46 PM
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Rockland County, New York, United States
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I am using the Pheonix 25 and the cutoff is set to 9 volts
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Old Jan 16, 2005, 08:35 PM
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Ben Lanterman's Avatar
St. Charles, MO USA
Joined Jan 2001
668 Posts
Isn't the cutoff voltage for one Lipoly cell about 2.6 volts or so. 9 volts would seem a little high maybe.

I use the same motor and battery (different name but same) but an Advance Jeti ESC and don't have any problems. It does an automatic setting.
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Old Jan 16, 2005, 09:59 PM
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Rockland County, New York, United States
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no for a lipoly cell it is 3 volts
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Old Jan 16, 2005, 10:40 PM
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Saskatoon, Canada
Joined Feb 2004
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Ynks, I have an SX2 with a Phoenix 10, Axi 2212/34, and used both an APC 11x4.7 and 10x4.7, always on the Thunder Power Gen1 3s830mah. I never watt-metered it, and the battery only got about 50 cycles, but I was always able to fly two 7 minute flights on a charge. I was pretty conservative on the throttle, with full throttle being rare, but your flight times certainly sound low. Really the only things that could cause your flight times to be so low are:
You have overheated and demagnetized your motor,
Your battery has been overheated, discharged too low, discharged too fast, charged too fast, or charged too high, or unbalanced,
You fly like a pylon racer with tons of throttle - but even at full throttle static I bet the 2208/34 on 3s w/ 9x3.8 draws at _most_ 8amps (i.e. five-six minutes until LVC),
Ambient temperature (lipo performance drops in the cold).

I was using a 9.0v cutoff.
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Old Jan 17, 2005, 01:48 AM
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Ben Lanterman's Avatar
St. Charles, MO USA
Joined Jan 2001
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To quote from the Battery Forum -

LiPolys act differently than NiCad or NiMH batteries do when charging and discharging. Lithium batteries are fully charged when each cell has a voltage of 4.2 volts. They are fully discharged when each cell has a voltage of 3.0 volts. It is important not to exceed both the high voltage of 4.2 volts and the low voltage of 3.0 resting volts or 2.5 during discharge. Exceeding these limits can harm the battery.
The way to ensure that you do not go below 2.5 volts while flying is to set the low voltage cutoff (LVC) of your electronic speed control (ESC). It important to use a programmable ESC since the correct voltage cutoff is critical to the life of your batteries. Use the ESC's programming mode to set the LVC to 2.5 volts per cell with a hard cutoff, or 3.0 volts per cell with a soft cutoff. If your ESC does not have hard or soft cutoff, use 3.0 volts per cell. You will know when flying that it is time to land when you experience a sudden drop in power caused by the LVC.

It would seem what kind of cutoff you are using makes a difference.
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Old Jan 18, 2005, 01:41 AM
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United States, CA, Stockton
Joined Jul 2002
185 Posts
I use the axi 2208/34 in my g-ride
3-cell 830
10x4.7 prop i thinks its drawing ~11 amps static

This setup has been working great even though its over the max reccomendations for the motor. I fly for about 7 minutes and wheni land everything is just barely warm
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Old Jan 18, 2005, 02:52 AM
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Airdrie, AB Canada
Joined Sep 2004
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Have you tried different packs? Cycle it on a charger, if you can, and read the mah in and out. I fly a 10x4.7 on my 2208/34, no LVC... flies for 10 minutes and comes down well above 9.0v.

Maybe a sticky bearing? Something rubbing? If you have a tach, and a wattmeter... compare your results to some others, might be something wrong with your motor causing to to draw more current or run inefficiently. It might be as simple as your LVC... but 2 minute runs would be 30C.... both pack and motor would be cooked. Something else is up, likely weak or damaged cells, or something with the motor. You'll have to measure to find it, or swap out known good components.

Mike
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Old Jan 19, 2005, 02:21 AM
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IsToR's Avatar
Stockholm, Sweden
Joined Aug 2004
341 Posts
Quote:
Originally Posted by Ynksrock510
I follow the charts on flyingmodels, and I still lose power. Im not understanding why. I built a mini 3dx. - i used 3 mm depron, 3 Futaba S3108 micro servos, foam safe CA, AXI 2208/34 - 830 mah 3s1p LiPo.
It has to be the foam safe CA that is the problem!
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Old Jan 19, 2005, 06:57 AM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
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I use the axi 2208/34 in my g-ride
3-cell 830
10x4.7 prop i thinks its drawing ~11 amps static

This setup has been working great even though its over the max reccomendations for the motor.


Labrother is living a charmed life! - he is correct that his set-up draws >11A - but yours is close to that, too (I measured 10.8A with a 9x3.8 on my test stand!) - that is well over the 8A max for the motor, and far too much for an 830 pack (especially if it is Gen I [?6C] and even Gen II [10C]).

My feeling is your battery is not up to it, because if you are at WOT (~11A) you can't expect your voltage to remain above 9v for long.

Cheers, Phil
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