Battery Size for Configuration? HELP
06-23-2004, 11:47 AM
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Battery Size for Configuration? HELP
Configuration: Speed 480 Gear 3:0:1 Prop 8.5X6
Would someone please reccomend the proper battery for this configuration on a Glider Super Dimona TC-80 (80" wingspan) about 42 oz. without battery... Please help me understand what kinds and what flight time I can expect out of different battery choices? I've been so confused moving from fuel to electric, because the information on battery to weight to power configurations is either VERY hard to find, or I just don't know where it is!?!
Thank you in advance for your help!
Would someone please reccomend the proper battery for this configuration on a Glider Super Dimona TC-80 (80" wingspan) about 42 oz. without battery... Please help me understand what kinds and what flight time I can expect out of different battery choices? I've been so confused moving from fuel to electric, because the information on battery to weight to power configurations is either VERY hard to find, or I just don't know where it is!?!
Thank you in advance for your help!
06-23-2004, 02:14 PM
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RE: Battery Size for Configuration? HELP
42oz is awful heavy, even on a glider, for the power you can get through a 480. It'll be 3 pounds or more with a battery, and I wouldn't use a 480 motor for anything over 2lbs ready-to-fly, even a glider.
That said, 480 motors like 10 cells best. I'd dump the 8x6 prop, though. That's not going to put enough load on the motor with a 3:1 gear ratio.
Don't let the confusion get you down. Remeber how you were when you started flying glow. Think about where you are now with respect to glow. It gets easier as you go along, but it takes time and effort on your part. Most likely, your inability to find information is due to the fact that you're looking for the wrong information. What you seek simply does not exist.
We determine how much power (Watts) we need based on the projected ready-to-fly weight of the airplane, with batteries, and how we plan on flying the airplane. This is just a guesstimate; you can be off by quite a bit and still be successful.
We then figure out what battery we need to sustain that power. We split up the Watts into Volts and Amps based on what would be reasonable values for the particular size plane we're working on, AND the total number of Watts needed. It's not reasonable, for example, to draw 40 Amps out of 1 cell to get 40 Watts for a small park flyer. Instead, we'd run 8 cells at 5 Amps. It is reasonable, however, to draw 40 Amps out of 10 cells to get 400 Watts for a .25ish-size, 4lb conversion.
With the maximum current, we can figure out which cells are suitable. For LiPolys, the maximum constant current ratings are in terms of C, or a multiple of their capacity in mAh. NiCd and NiMH information is not "officially" available, since the companies that manufacture the cells (e.g. Sanyo) didn't design their cells for R/C. You can get the information you seek by poking around forums, or by simply asking.
Now comes the part where we effectively apply that power to the air to make the plane go. This is where things get sticky. You need to spec out a motor that can handle the cell count and current previously determined, then either prop or gear-and-prop it to draw the desired current, depending on the motor. The hard part is propping the motor such that it provides both adequate thrust and adequate speed to fly the airplane. It's easy to end up with a plane that has a 2:1 thrust to weight ratio, but won't fly horizontally.
A 2m sailplane is a bit too much for a 480 motor. I'd recommend you look into 550/600/modified car motor power systems on about 8 Sub C NiCd or NiMH cells.
That said, 480 motors like 10 cells best. I'd dump the 8x6 prop, though. That's not going to put enough load on the motor with a 3:1 gear ratio.
Don't let the confusion get you down. Remeber how you were when you started flying glow. Think about where you are now with respect to glow. It gets easier as you go along, but it takes time and effort on your part. Most likely, your inability to find information is due to the fact that you're looking for the wrong information. What you seek simply does not exist.
We determine how much power (Watts) we need based on the projected ready-to-fly weight of the airplane, with batteries, and how we plan on flying the airplane. This is just a guesstimate; you can be off by quite a bit and still be successful.
We then figure out what battery we need to sustain that power. We split up the Watts into Volts and Amps based on what would be reasonable values for the particular size plane we're working on, AND the total number of Watts needed. It's not reasonable, for example, to draw 40 Amps out of 1 cell to get 40 Watts for a small park flyer. Instead, we'd run 8 cells at 5 Amps. It is reasonable, however, to draw 40 Amps out of 10 cells to get 400 Watts for a .25ish-size, 4lb conversion.
With the maximum current, we can figure out which cells are suitable. For LiPolys, the maximum constant current ratings are in terms of C, or a multiple of their capacity in mAh. NiCd and NiMH information is not "officially" available, since the companies that manufacture the cells (e.g. Sanyo) didn't design their cells for R/C. You can get the information you seek by poking around forums, or by simply asking.
Now comes the part where we effectively apply that power to the air to make the plane go. This is where things get sticky. You need to spec out a motor that can handle the cell count and current previously determined, then either prop or gear-and-prop it to draw the desired current, depending on the motor. The hard part is propping the motor such that it provides both adequate thrust and adequate speed to fly the airplane. It's easy to end up with a plane that has a 2:1 thrust to weight ratio, but won't fly horizontally.
A 2m sailplane is a bit too much for a 480 motor. I'd recommend you look into 550/600/modified car motor power systems on about 8 Sub C NiCd or NiMH cells.
