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Noob power system questions

Old 11-21-2018, 05:26 PM
  #1  
__almost
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Question Noob power system questions

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).

Motor: ebay . com/itm/RC-2200KV-Brushless-Motor-A2212-6-30A-ESC-Propeller-Kit-For-RC-Airplane/272602664248
Battery: ebay . com/itm/5000mAh-3S-11-1V-30C-LiPo-Rechargable-Battery-XT60-1042125B-For-RC-Plane-Drone/302623827672

Thanks for the help!

- Almost.
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Old 11-22-2018, 01:04 AM
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quorneng
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- almost
The A2212-6 2200kv can just about give 260W continuous which translates to just under 100W/lb for a 1.3 kg plane but how well it all flies is going to depend pretty much on what sort of 1.3 kg plane it is.
A 2700kV motor will be turning a small prop rather fast fast (20,000 rpm?) on a 3s which is not a particularly efficient way of doing things. At that power it will be drawing close to 30A so everything will need plenty of cooling air.

If it needs say 25A to stay in the air it will fly for about 12 minutes.
If the plane is a slow flyer you would do much better to use a lower kv version (1000kv) of the motor and turn a bigger finer pitch prop. At only 10A (110W) it will still produce nearly the same low speed thrust as the 2200kV motor and the flight time will be nearly 3 times as long.

Now if you can make it all lighter (say 0.75 kg?), aerodynamically efficient and still fly slowly the power to fly can drop to just a cofew amps. The endurance on your 5000 mAh battery will then shoot up to an hour or more.

It can be done but it does get a bit specialised.
This uses a 5000mAh 2s.
Name:  18Sep17.JPG
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After two hours I realised it could fly longer than I could so I gave up!
The battery was still at 50%.
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Old 11-22-2018, 11:04 AM
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__almost
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Originally Posted by quorneng View Post
- almost
The A2212-6 2200kv can just about give 260W continuous which translates to just under 100W/lb for a 1.3 kg plane but how well it all flies is going to depend pretty much on what sort of 1.3 kg plane it is.
A 2700kV motor will be turning a small prop rather fast fast (20,000 rpm?) on a 3s which is not a particularly efficient way of doing things. At that power it will be drawing close to 30A so everything will need plenty of cooling air.

If it needs say 25A to stay in the air it will fly for about 12 minutes.
If the plane is a slow flyer you would do much better to use a lower kv version (1000kv) of the motor and turn a bigger finer pitch prop. At only 10A (110W) it will still produce nearly the same low speed thrust as the 2200kV motor and the flight time will be nearly 3 times as long.

Now if you can make it all lighter (say 0.75 kg?), aerodynamically efficient and still fly slowly the power to fly can drop to just a cofew amps. The endurance on your 5000 mAh battery will then shoot up to an hour or more.

It can be done but it does get a bit specialised.
This uses a 5000mAh 2s.
Attachment 187176
After two hours I realised it could fly longer than I could so I gave up!
The battery was still at 50%.
Thank you for the reply!, it's really helpful.
I think I would go for a 1000kv, it does seem like a better choice.
I'll also see if i can in any way reduce the overall weight of the plane.

Thanks!
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Old 11-22-2018, 12:37 PM
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solentlife
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My two pence worth ...

Do not buy batterys and motors of eBay unless its only route.

Try to use Hobby King ... Motion RC .... RC Timer ... HeadsUp RC or some real model seller. eBay is full of reject items and second grade ... plus prices are often silly.

OK ... 1.3Kg is a moderately heavy Foam plane especially if a beginner. And as Q says - that motor will be asking for a small high revving prop - probably around the 6x4 size.

Depending on the intended use of the plane - you can narrow down the power side ...

Slow flyer and trainer - needs a low to moderate KV with a reasonable size prop ... model usually in the 700 - 1000gr arena. That would put a 28 to 32 size motor ... 8 - 9" x 6 prop and about 1000kv.

Moderate speed intermediate of similar size / weight and motor ... maybe with a higher pitch prop.

High speed model in the 500 - 700 range with your high revving motor on a 6x4 ... 6x5 prop etc.

There's more to this than just will it fly.

eCalc.com - is a great tool to use to get to decide prop / battery / ESC combos for plane size / weight etc. Input numbers ... play around till you get what you look for.

Finally - can you give us a sketch or idea of the plane you intend for ... and what is your RC flight experience ?

Nigel
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Old 11-22-2018, 03:34 PM
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ron_van_sommeren
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Originally Posted by quorneng View Post
... If the plane is a slow flyer you would do much better to use a lower Kv version (1000rpm/volt) of the motor ...
Lower rpm would also reduce the dreadful (pusher configuration) racket a bit.
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Old 11-22-2018, 04:16 PM
  #6  
__almost
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Originally Posted by solentlife View Post
My two pence worth ...

Do not buy batterys and motors of eBay unless its only route.

Try to use Hobby King ... Motion RC .... RC Timer ... HeadsUp RC or some real model seller. eBay is full of reject items and second grade ... plus prices are often silly.

OK ... 1.3Kg is a moderately heavy Foam plane especially if a beginner. And as Q says - that motor will be asking for a small high revving prop - probably around the 6x4 size.

Depending on the intended use of the plane - you can narrow down the power side ...

Slow flyer and trainer - needs a low to moderate KV with a reasonable size prop ... model usually in the 700 - 1000gr arena. That would put a 28 to 32 size motor ... 8 - 9" x 6 prop and about 1000kv.

Moderate speed intermediate of similar size / weight and motor ... maybe with a higher pitch prop.

High speed model in the 500 - 700 range with your high revving motor on a 6x4 ... 6x5 prop etc.

There's more to this than just will it fly.

eCalc.com - is a great tool to use to get to decide prop / battery / ESC combos for plane size / weight etc. Input numbers ... play around till you get what you look for.

Finally - can you give us a sketch or idea of the plane you intend for ... and what is your RC flight experience ?

Nigel
Hi Nigel thanks for the reply,
Unfortunately, for the time being I'll have to go with ebay (due to tight budget and the fact that I do not live in either the US or Europe).

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.

So I think that I'll go for a twin plane with the 1000kv versions of the motors in my original post.

Thanks,
-Almost
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Old 11-22-2018, 04:31 PM
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AEAJR
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Be sure to read this free on-line book.

EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
www.wattflyer.com/forums/showthread.php?t=31368

If you are going to scratch build your own planes, naturally you will be optimizing a power system to each plane.

You need a wattmeter to test any system you buy. For example this one:
https://hobbyking.com/en_us/hobbykin...-analyzer.html

In the ad it says that the motor is for 2-3S battery. And it includes a prop. But it doesn't say what battery that prop is matched to. If you run 2S you would use one prop. If you run 3S you would use a different prop. Higher voltage means you need a smaller prop. You need to send a note to the seller asking what battery that prop is matched to.

As for powering your scratch built plane, the general range is 75 watts/pound for moderate performance, light aerobatics. 100 watts/pound for sport plane, more aggressive aerobatics, higher speed flight or a fast climb on a glider. 150 watts/pound for all out aerobatics, light 3D flying or competition sailplane climbs.

1.3 KG = 2.86 pounds. So you want something between 215 watts and 430 watts.

This motor is rated for a max of 342 watts, so it is definitely in the range, depending on the performance you expect.

342 watts/2.86 pounds = 119 watts/pound, probably a good match. But I would want to put it on the Wattmeter when I get it to be sure that what I expect is what I am getting.

If you are using a pusher design, check the prop clearance to the boom. You want to be sure you have some clearance there as the boom will flex and you don't want the prop hitting it or it might cut the tail off, break the prop or rip the motor off the mount.

If you are using landing gear, be sure to leave enough room for tail up/take off and coming in a bit low as you don't want the prop to hit the ground.

Hope that helps.
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Old 11-22-2018, 04:45 PM
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I moved this to Power Systems as it seems a better match for the question.
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Old 11-22-2018, 04:51 PM
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Motors, batteries,FPV gear, etc you can't do much to save weight = apart from buying lighter - but the air frame is to a degree DIY so it pays to spend time designing it not simply for strength but to achieve the best strength to weight ratio.

The ideal is of course for every part of the air frame to be just strong enough for the required duty. This is particularly true for the parts that don't carry much load but for a model it is not easy to establish what strength is actually needed.

As an example with any monoplane wing the maximum bending moment occurs at the root with little or none at the tip so there are considerable weight saving to be had if a wing is built with that in mind.

I have to agree with solentlife it would be wise to hold off ordering motors, speed controllers and batteries until you know what the actual weight of the plane is and how its aerodynamics end up.

Do keep us informed of how this project goes.

AEJR
I did note that particular motor is rated for 342 Watts but for just 12 seconds. Many of the reviews suggested it still got very hot at significantly lower Watt figures.
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Old 11-22-2018, 05:11 PM
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AEAJR
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quorneng,

I don't know that motor. To what reviews do you refer. Can you provide a link?

Let's run the numbers.

Says max continuous current is 30 amps 30 X 11 V = 330 W ( close to the max watt number)
Many prefer to do the calculation at 10 V = 300 W

Max peak current, 12 seconds 45 amps X 11 V = 495 W
Again, doing this at 10 V = 450 W for 12 seconds

So the 342 watt number seems to be based around the 30 amp continuous rating. Just my analysis of the ad. Again, I don't know this motor. And if you will be doing mixed flying, meaning some partial throttle flying, then the average will be well below the 342 number.

I had not noted earlier that the package comes with a 30 amp ESC which leaves no margin for error. I would want at least a 40 amp ESC on this motor if I was going to run it near that 30 amp number. Continuous running at 30 amps might cook that ESC if it has any sort of cooling/airflow issues.

Again, that is why we use wattmeters, to see what the system is actually doing, not what we think it is doing. Many a plane has been lost due to an overloaded motor/ESC or battery.
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Old 11-22-2018, 08:57 PM
  #11  
__almost
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Originally Posted by AEAJR View Post
Be sure to read this free on-line book.

EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
www.wattflyer.com/forums/showthread.php?t=31368

If you are going to scratch build your own planes, naturally you will be optimizing a power system to each plane.

You need a wattmeter to test any system you buy. For example this one:
https://hobbyking.com/en_us/hobbykin...-analyzer.html

In the ad it says that the motor is for 2-3S battery. And it includes a prop. But it doesn't say what battery that prop is matched to. If you run 2S you would use one prop. If you run 3S you would use a different prop. Higher voltage means you need a smaller prop. You need to send a note to the seller asking what battery that prop is matched to.

As for powering your scratch built plane, the general range is 75 watts/pound for moderate performance, light aerobatics. 100 watts/pound for sport plane, more aggressive aerobatics, higher speed flight or a fast climb on a glider. 150 watts/pound for all out aerobatics, light 3D flying or competition sailplane climbs.

1.3 KG = 2.86 pounds. So you want something between 215 watts and 430 watts.

This motor is rated for a max of 342 watts, so it is definitely in the range, depending on the performance you expect.

342 watts/2.86 pounds = 119 watts/pound, probably a good match. But I would want to put it on the Wattmeter when I get it to be sure that what I expect is what I am getting.

If you are using a pusher design, check the prop clearance to the boom. You want to be sure you have some clearance there as the boom will flex and you don't want the prop hitting it or it might cut the tail off, break the prop or rip the motor off the mount.

If you are using landing gear, be sure to leave enough room for tail up/take off and coming in a bit low as you don't want the prop to hit the ground.

Hope that helps.
It sure does help!
Thanks a lot
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Old 11-22-2018, 09:31 PM
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__almost
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Originally Posted by quorneng View Post
Motors, batteries,FPV gear, etc you can't do much to save weight = apart from buying lighter - but the air frame is to a degree DIY so it pays to spend time designing it not simply for strength but to achieve the best strength to weight ratio.

The ideal is of course for every part of the air frame to be just strong enough for the required duty. This is particularly true for the parts that don't carry much load but for a model it is not easy to establish what strength is actually needed.

As an example with any monoplane wing the maximum bending moment occurs at the root with little or none at the tip so there are considerable weight saving to be had if a wing is built with that in mind.

I have to agree with solentlife it would be wise to hold off ordering motors, speed controllers and batteries until you know what the actual weight of the plane is and how its aerodynamics end up.

Do keep us informed of how this project goes.

AEJR
I did note that particular motor is rated for 342 Watts but for just 12 seconds. Many of the reviews suggested it still got very hot at significantly lower Watt figures.
Thanks for that, I'll keep that in mind!

I will also post on this thread if I'll have any more questions or problems on the project, and hopefully when it's done make a post to share my experience.

I also have to say that this is a great community and that I'm really surprised by the effort you guys put into your answers, so thank you all!
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Old 11-23-2018, 07:17 AM
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Wattflyer is well known for its help and wish for all to enjoy the sport. We all started at the base line ... we all are still learning. Unlike some other forums - we remember our humble beginnings and try to help others through.

Do not worry how simple or silly it may seem - post it / ask it ... we will advise / suggest / help with hope end result works.

Nigel
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Old 11-23-2018, 12:34 PM
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ron_van_sommeren
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Training/trainer suggestions:
Advice for getting into flying RC airplanes, and how not to - The Ampeer

Some well-structured reading and handy e-tools for rainy/windy days. Will save you, and us a lot of questions. Notably the 'what went wrong?' kind of questions Will also prevent you from burning up several controllers and/or motors and/or battery:
E-flight primer and tools

And pleasepleaseplease, do your RC equipment, wallet, ego, battery, controller, motor, house/garage/car a big favour ... get a watt-meter. It will more than pay for itself, will save you at least one fried motor and one fried controller. Will also help you finding the best setup.
Keep battery/-watt-/multi-meter wires short!
too long wires batteryside will kill ESC over time: precautions, solutions & workarounds
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