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Help! Noob power system questions

#1
Hi all,
I'm new to this site so please let me know if this isn't the place for questions such as these.

Long story short, here are the questions:
1) Can an A2212-6 2200KV motor (with the provided ESC and prop) connected to a 5000mAh 3S 30C LiPo be used to power a DIY foam plane weighing 1.3kg? (weight is including the battery).
2) If not, then what about connecting two of those motors and ESCs in parallel to the same battery mentioned above?
3) What is the estimated flight time that I'm looking at? (In any of these scenarios).

Thanks for the help! :)

- Almost.
 

Merv

Well-known member
#2
Long story short, here are the questions:
No, I doubt your setup would fly. I doubt twin motors would fly, if so it will be underpowered. Four of them would work. I'd recommend a much larger motor or a smaller battery (1300-1800 mah). My flight times are 6-10 minutes, a lot depends on how you fly.
 
#3
No, I doubt your setup would fly. I doubt twin motors would fly, if so it will be underpowered. Four of them would work. I'd recommend a much larger motor or a smaller battery (1300-1800 mah). My flight times are 6-10 minutes, a lot depends on how you fly.
Thank you :)
 

d8veh

Well-known member
#4
2200kV is a little on the fast side. You'd be better with the 950kV or 1000kV version (probably the same), which works very well with the provided 10x 4.5 propeller. It'll draw about 21 amps with that propeller, and it gives somewhere close to 1kg thrust at full throttle. They give really good performance with a 600g to 800g plane. A 1300g one will work, but won't have sparkling performance. It depends what you want to do with it. the 2200kV one would work, but you'd need to go down to something like a 7x4 or maybe 8x3 propeller to keep the current down.

5000mAh is a relatively big battery. A 1300mAh lasts about 5 minutes of mixed flying with an all-up weight of around 800g, so the 5000mAh one on a cruising plane would last about 15 minutes.

If you tell us more about the plane, we can give better advice.

1000kv version:

https://www.ebay.com/itm/A2212-1000...=item3d7a5a4fa9:g:H1cAAOSwnbZYHVHy:rk:29:pf:0
 

DamoRC

Well-known member
Mentor
#5
Hi all,
I'm new to this site so please let me know if this isn't the place for questions such as these.

Long story short, here are the questions:
1) Can an A2212-6 2200KV motor (with the provided ESC and prop) connected to a 5000mAh 3S 30C LiPo be used to power a DIY foam plane weighing 1.3kg? (weight is including the battery).
2) If not, then what about connecting two of those motors and ESCs in parallel to the same battery mentioned above?
3) What is the estimated flight time that I'm looking at? (In any of these scenarios).

Thanks for the help! :)

- Almost.
Agree with @d8veh that more information on the plane would be helpful (wingspan, wing area etc)

That being said, with the setup described your max power to weight is ~120 Watts per pound which is enough to fly based on a general power to weight rule of thumb:

"Less than 50W/lb - very lightweight / low wing loading slow flyer.
50 to 80 W/lb - light powered gliders, basic park flyers and trainers, classic biplanes and vintage ('Old Timer') type planes.
80 to 120 W/lb - general sport flying and basic/intermediate aerobatics. Many scale ( eg warbirds) subjects suit this power band.
120 to 180W/lb - more serious aerobatics, pattern flying, 3D and scale EDF jets.
180 to 200+W/lb - faster jets and anything that requires cloud-punching power!"

So I would think that with a reasonably low wing loading (this the request for wing area / specs) you plane will fly on this setup.

DamoRC
 
#6
2200kV is a little on the fast side. You'd be better with the 950kV or 1000kV version (probably the same), which works very well with the provided 10x 4.5 propeller. It'll draw about 21 amps with that propeller, and it gives somewhere close to 1kg thrust at full throttle. They give really good performance with a 600g to 800g plane. A 1300g one will work, but won't have sparkling performance. It depends what you want to do with it. the 2200kV one would work, but you'd need to go down to something like a 7x4 or maybe 8x3 propeller to keep the current down.

5000mAh is a relatively big battery. A 1300mAh lasts about 5 minutes of mixed flying with an all-up weight of around 800g, so the 5000mAh one on a cruising plane would last about 15 minutes.

If you tell us more about the plane, we can give better advice.

1000kv version:

https://www.ebay.com/itm/A2212-1000...=item3d7a5a4fa9:g:H1cAAOSwnbZYHVHy:rk:29:pf:0
Thank you so much for the help :)
Some background about the plane is that it's for a FPV like school project, and still in the planning/building phase. Therefor I don't have specs about the plane to give you guys at the moment (other than the weight that is the sum of the parts that I know I would need and a liberal estimate of the weight of the finished foam plane - that is still being built).
It's meant to be a cruise plane so it doesn't have to be too fast or do crazy acrobatics. Also due to the project's nature, I'd prefer a longer flight time over a short one and ~15 minutes of flight sounds pretty good.

I looked at the 1000kv version that you've provided, and it seems like a much better choice for a cruising plane - so thank you for that also!

And just to clarify, in your answer do you refer to the one motor setup or the two motor setup?

Thanks again!
-Almost
 
#7
Agree with @d8veh that more information on the plane would be helpful (wingspan, wing area etc)

That being said, with the setup described your max power to weight is ~120 Watts per pound which is enough to fly based on a general power to weight rule of thumb:

"Less than 50W/lb - very lightweight / low wing loading slow flyer.
50 to 80 W/lb - light powered gliders, basic park flyers and trainers, classic biplanes and vintage ('Old Timer') type planes.
80 to 120 W/lb - general sport flying and basic/intermediate aerobatics. Many scale ( eg warbirds) subjects suit this power band.
120 to 180W/lb - more serious aerobatics, pattern flying, 3D and scale EDF jets.
180 to 200+W/lb - faster jets and anything that requires cloud-punching power!"

So I would think that with a reasonably low wing loading (this the request for wing area / specs) you plane will fly on this setup.

DamoRC
Hi, thank you for the reply :)
As I mentioned in my reply to @d8veh, I unfortunately don't have much specs about the plane at the moment other than the weight and desired flight characteristics because I'm still planning and building it.
Also, when you say "~120 Watts per pound" do you mean with one or two motors?

Thanks!

P.S: Because I'm new to this field I try to absorb as much knowledge as I can, and comments like yours really help! I did not know that rule of thumb before.
 

FDS

Well-known member
#8
120w per pound would be a function of the sum of all motors power output, so whatever the W output per motor, times the number of motors = total power output. Divide that by the mass in pounds to get the W/pound.
 

d8veh

Well-known member
#9
If that table above is output power, it's a bit worse than it looks. The problem is 21 amps x 12v = 252w input, not output. It's difficult to gauge the output because we don't know the efficiency factor, which would be somewhere around 70%, so something like 176w output and close to 62w per pound. It's marginal. I think I'd be looking at two motors on the basis that if you have too much power, you can always turn it down, but if one motor isn't enough, you can't turn it up.

You can run two motors off one battery if you make or buy a Y-lead to the ESCs.

Another thing: It would probably be OK with a 4S battery, in which case you'd need a 9x4 propeller and an ESC capable of handling 4S. Some of the cheap ESC, like those yellow ones are for 2S and 3S only.
 

Merv

Well-known member
#10
the plane is that it's for a FPV like school project, and still in the planning/building phase.... I'd prefer a longer flight time over a short one and ~15 minutes of flight sounds pretty good.
I'd recommend you start with a known designs for an FPV platform. The Bixler or something similar would be an excellent choice. If you need or want to build it as part of the project, I'd recommend the AXON or the Ansley Peace Drone both are capable of 15 min flight time. Ed form Experimental Airlines did a great job on both.
 
#11
If that table above is output power, it's a bit worse than it looks. The problem is 21 amps x 12v = 252w input, not output. It's difficult to gauge the output because we don't know the efficiency factor, which would be somewhere around 70%, so something like 176w output and close to 62w per pound. It's marginal. I think I'd be looking at two motors on the basis that if you have too much power, you can always turn it down, but if one motor isn't enough, you can't turn it up.

You can run two motors off one battery if you make or buy a Y-lead to the ESCs.

Another thing: It would probably be OK with a 4S battery, in which case you'd need a 9x4 propeller and an ESC capable of handling 4S. Some of the cheap ESC, like those yellow ones are for 2S and 3S only.
Thanks for the advice,
looks like I would go for a twin 1000kv to be on the safe side.
 
#12
I'd recommend you start with a known designs for an FPV platform. The Bixler or something similar would be an excellent choice. If you need or want to build it as part of the project, I'd recommend the AXON or the Ansley Peace Drone both are capable of 15 min flight time. Ed form Experimental Airlines did a great job on both.
Looks like a solid design, I'll definitely make some modifications to try and make mine similar to this one.
Thanks!