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How Many Cells Do I need?

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Old 09-15-2015, 07:45 PM
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jumbodrawn
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Default How Many Cells Do I need?

Hi!

Im planning on building an airplane. It will be the FT Guinea pig, and this is the electrics I will be using:

http://store.flitetest.com/power-pac...e-twin-engine/

I plan to use the DX7 2G which I believe uses the AR8000 reciever.
I have a few questions. First of all, how many cells do I need? Does it matter? I'm thinking about 10, 000 mah is good. On a side note, how will I wire two motors to one throttle pinout? Does the reciever get power from the esc's pwm cables rhemselves? Also on a side note I'm not using differential thrust.
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Old 09-25-2015, 10:30 AM
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aeajr
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These are the specs I picked up from the link you provided:

Contains everything needed to power one of our Swappable (twin engined) Planes. This kit completes everything you need to build our twin engined Swappable airplanes. The only other components you will need to fly is a Y-harness to power the motors, a battery/charger and transmitter/reciever. The included motor and ESC comes presoldered with 3.5mm Bullets and XT60 Connector. We set out from the beginning to make this great hobby more approachable and these all in one electronics packs are another step in that direction.

Pack Includes:
  • (2) Motor - Emaxx GT2215/09
  • (2) ESC - BL Heli 30 amp ESC
  • (6) Servos - 9 Gram Emaxx servo
  • (1) Y-Lead (12")
  • (4) Extensions (12")
  • (6) Linkage Stoppers
  • (4) Propellers - 10x4.7 (2x Clockwise & 2x Counter Clockwise)
  • (1) Allen Wrench (1.5mm)
  • (1) Screwdriver (phillips)
  • (1) Custom Flite Test Lipo Bag (8"x10")

The battery pack you need is determined by the motor and the prop. How did you select this power pack? Is this the one recommended for this plane?

I see this is your plane:
http://store.flitetest.com/ft-guinea-pig/

I could not find any specs on the site where you are buying the power pack so I looked elsewhere:

EMAX GT Series Motor Features:
1.Easy to revert output shaft direction
2.Adopts 0.2mm silicon steel, ensures high performance and low temperature
3.Compare to other series motors, the GT Series are more precise, lighter in weight and higher in efficiency
4.GT Series motors have a better compatibility with more different speed controllers and propellers
5.GT Series utilizes imported bearings
Type: GT2215/09
RPM/V: 1180 RMP/V
Weight: 70g/2.46oz
Dimension: 28.5mm (Dia) x 33.5mm (Length)
Shaft diameter: 4 mm
Max thrust: 1100g
Cell number: 3S Lipo
Recommended prop size: 10x6/10x4.7


Based on this information you need a 3S pack. I can't find any specs on what the motor will draw with a 3S pack with a 10X4.7 prop so ran it through e-calc assuming a 2500 mah 30 C pack per motor. The estimate is about 26 amps and the motor will run hot so you better make sure you have plenty of cooling air flowing over the motor. That should give you about 7-12 minutes of mixed power flying time depending on how hot you are on the throttle.

Last edited by aeajr; 09-25-2015 at 10:50 AM.
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