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Long range / flight time with parallel batteries & other questions

Old 12-05-2019, 08:23 PM
  #1  
MD_R
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Post Long range / flight time with parallel batteries & other questions

Hey all, I have some beginner questions I thought I'd ask you before I get started with a project. I don't have any experience with RC in general and have only just started to become interested so forgive me if I use the wrong lingo or just generally know nothing.

I'm purchasing a 3D printer soon and one idea I had is to try to create a long range RC prop plane. I am kind of wondering what I could do with something like an Arduino or Raspberry Pi acting as the brains of the vehicle, and connect to it (perhaps with an FPV camera) over a 4G network, which you can find a few examples of this type of thing online in various places as others have thought of this before me. And with this type of setup I'd probably have a notebook computer with a game controller (xbox) to act as the flight controls of the vehicle - as well as use a simple auto pilot setup on board to allow the vehicle to maintain control if the mobile data connection is lost (what, like a PixHawk?). I understand this is a very complicated setup and certainly not an ideal beginner project - but we will just like... not talk about that haha. I do have a good bit of experience working with code and should be able to cobble together the work of people smarter than me to make that kind of thing work in theory, but I have some critical questions I need experts (or at least people more experienced than me with RC) to help me out with that are more directly related to your standard RC airplanes.

So now, I hope to try and print out body parts in sections and then later fasten and glue the parts together to form the wings and body of the plane. But the things I'm really wondering are about reaching a very long distance / flight times with an RC vehicle in general. I understand from doing a bit of research that there are a wide variety of motors, ESCs and batteries to choose from, and that as far as I can tell the vast majority of the hardware is geared towards relatively short flight times at fairly high speeds. Correct me if I am wrong but it seems most combinations on a normal RC plane might run for 25 - 45 minutes (though it seems some go a bit longer than that). And if that vehicle could go roughly 80MPH then you could expect it to cover about 33-60 miles from a full charge (again I'm guessing I'm brand new to this haha).

So I got to thinking that if I tried running several large packs in parallel that I could increase the run time by a lot, though in the process I'd be adding great amounts of weight to the plane. That would mean I'd need a more powerful motor to be able to carry the 3D printed vehicle as well as its battery packs and lift off. Right? Or does all this sound like complete nonsense, and I should try and buy super expensive high capacity packs instead (I've seen some that go into the 10,000 mAH range)? I've seen videos and articles showing HOW to run parallel battery packs on RC vehicles, but not too much detail on how to do it safely, or what kinds of limits to consider...

Is this something you could share experience on? Have you tried getting very long flights by using sets of batteries? I worry that by using many batteries (lets say four as an example) that even if the voltage is still the same, it would somehow potentially cause damage to have them all connected to a single ESC. Is there any advice on ways to prevent problems by doing that? Is there a good rule to use when it comes to cell counts and things like this? Or does it really make no difference and its just that simple, and by hooking more identical batteries up, and assuming there is enough power to get it to take off then it will be just fine? If a motor is rated to run just fine with just one of those batteries - then it should have no problem running with as many as four of them in parallel? I also assume that the lengths of wire ran from each pack should be identical, and that contact should be consistent to prevent the batteries from draining at an uneven rate, or is length not a huge factor, just the solder consistency at the connections?

Is there any other pitfalls to worry about - is it possible to burn up motors or ESCs by just running them way longer than the manufacturer expected you to? Will long flight times (lets guess I somehow get it going for several hours at a time) pose any other problems with electronics that might not have happened in a normal runtime on a single battery pack?

While I have you - what is up with center of gravity? Should I try and make sure the vehicles COG is right between the wings at the fuselage? Perhaps slightly behind or in front of the wingspan? What is a good plan to arranging the weight of the vehicle?
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Old 12-05-2019, 09:35 PM
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Well...let's just ignore the other thousands of pitfalls you're setting yourself up for, and concentrate on the question you asked. In theory, you can have as many batteries in parallel as you want. But as you noted, heat is your enemy, so yes, it is very possible to burn things up by running too long. Proper sizing of components and designing in lots of cooling airflow can help overcome that issue. As an example, I have a high power plane that lasts 4-5 min. on a pack. If I was able to fly with 4 packs (more on that in a minute), I have no doubt I would be at burning up the motor and/or the ESC due to heat build up. But, I have a friend that does UAS research at the local University, with automated piloted vehicles, and by good engineering, he is able to get well over an hour of autonomous flight for aerial surveys. I'm sure he could engineer up a system that would go far longer, but hasn't as his research needs don't require it. Many have designed and flow very, very long duration planes - so it can be done, but takes a lot of in depth engineering of the whole vehicle to achieve the goal.
You'll need to study up a lot on aerodynamics - more payload (batteries) means much more weight. Meaning more wing to lift the weight. Meaning more power to overcome the inherent drag of a larger wing and associated structures of the vehicle.
Proper CG depends on the configuration of the plane and the specific shape of the wings - swept back, delta, rectangular, etc. Do a google search and you'll find some basic rules of thumbs for how to find a starting point for defining where it should be....but again I refer you back to learning a lot more about aircraft design.
Start with baby steps - 3D printed planes tend to be relatively very heavy, so be happy if your first can even fly for a couple of minutes, without all the automation. Then start working on improved versions that get you further along to your goal....

You would be well served to just buy a "trainer" type electric plane, and learn all you can about flying with it (with the help of an instructor) as the very first step. Then move on to a few more that relate to your overall goal to gain experience on those...and then begin your journey on designing your own....

Last edited by tedsander; 12-05-2019 at 09:41 PM.
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Old 12-05-2019, 10:06 PM
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I suppose I had better start doing my homework!

I know that doing 3D printing for the structure has advantages and disadvantages - and yes if I am not very careful in how I structure the infill of the shape of the vehicle it will either end up very heavy with lots of infill, or very weak structurally with very little infill, and that might mean a heavier overall vehicle. What your saying about the heavier payload and more lift problem I suppose means I'd need a larger wingspan to provide more lift as well as a more powerful engine than I might otherwise need in turn.

I should probably point out that I am not very interested in using any kind of off the shelf (or digital shelf) plane body - as I would really like to experiment with building the shape and printing it - even if I do base the shape on an existing wing shape to try and use a more proven design rather than one of my own that might not have ideal aerodynamics and such. I think that while 3D printing the body may force a higher weight, it also allows for rapid prototyping of the shape of the plane. If something isn't quite right for fitting the internals, I can make adjustments and print the sections which need to be replaced. I suppose its fair to say that by printing a design I can make sure its *just* big enough to hold all the internals tightly, with no wasted internal space.

The printing and designing part is probably most of what has my interest in making an RC vehicle at all, I guess I am just a creative minded person and have less interest in reusing the wheel someone else made, and more interest in reinventing it haha.

And yes you may be right, and I'd be lucky to have it lift off the ground let alone be able to maintain flight for a long period of time. I suppose I'm very impressed with youtube videos like "RC Endurance build explained" (I can't post links, url ends in watch?v=nZkzJSkzte8) and I think it would be really cool to try and get results like that out of a fixed wing craft on all electric power - and even cooler if I design and build the thing myself!

So I guess the main point though - your saying that regardless how many batteries you put into parallel it really shouldn't matter from a standpoint of instantly frying the electronics or something like that? Would it make more sense to go and get a bunch of 18650 cells and solder up a pack myself that meets a certain spec? I really don't wanna risk that as I figure it can be trickier than just wiring existing packs into parallel... But then again I've seen some of the guys doing that sort of thing to maximize their range.

As far as heat damaging the electronics from being operated too long, I wonder if having a port or duct to pass air through and over the electronics would help with that? Is that pretty standard? Might not be great for a sudden rain popping up :X

Anyway thank you for your input, I'll consider all these and try and decide what the right thing to do is!

Last edited by MD_R; 12-05-2019 at 10:08 PM.
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Old 12-06-2019, 07:00 AM
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Start with this book: R/C Model Airplane Design or this one: Basics-Model-Aircraft-Design-Techniques
From there, Amazon will lead you to bazillions more, both about RC airplanes, and full scale - which all have STRONG bearing on whether yours will fly or not.

I chatted with my friend, and he leads a small group of aeronautical grad students in designing planes just for the kind of autonomous flight you are thinking about. They have years of high level aeronautical engineering classroom learning...but NO experience in building/flying. So with each new group is the build/try-to-fly/crash scenario. Usually due to either pilot error, or initial design flaws. Not at all saying you need the years of learning, just pointing out that theory and real world collide pretty often, even for those that should know more than enough, so be prepared for setbacks. We've all been there. But with sticking to it, it can be done.

Yes, cooling airflow is critical. As is selecting the components that minimize power consumption (less heat, longer flight time on a given battery amount) - but still produce enough for flight.

3D printing is its own challenge, but in the real world I can build a basic plane from scratch using traditional materials (balsa, etc.). in less time than a printer would take. Far, far less if I went with something like foam board. Consider both methods - very fast and dirt cheap for proof-of-concept, then printed for refined design.

In the end, do what you have fun doing - it's up to you to decide whether this is just something to make an attempt to mess around with for a bit, or if one aspect or more of the subject (aerodynamics, 3D structural design, electronics and coding) appeals to you for a deeper dive.

Last edited by tedsander; 12-06-2019 at 07:10 AM.
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Old 12-06-2019, 10:30 AM
  #5  
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Thanks for the encouraging words! I certainly hope its something that would make a fun hobby at the very least, even if all my ideas fail I hope to have fun ya know?

I will look into these books and see if I can get a copy locally - that would probably be a big help during the initial "idea" phase I'm in. I don't plan on ordering any electronics or really even beginning to print anything until I have a solid understanding of what I will be doing, and what all will go into it, because I'd hate to pour many hours and money into it only to find that it only serves as a paper weight, haha.

I will most likely spend a good bit of time getting used to the printer, as that is somewhat new to me - though I have experience in 3D modelling I have yet to try my hand at actually printing stuff out, which will have a learning curve as well. Once I think I'm confident with the printer and the material I'll be using I will only then start to look into the body design. I do like the idea of maybe trying other materials (wood, foam) and seeing if I can work out a concept that way, but I don't know for sure I'd be very good at that, and might be better off sticking to a 3D print just because I have experience on the software side of thing, while with woodworking or just foam cutting and shaping I would be a bit out of my element I think. I'll keep that in mind though as that does make sense.

I've found many plans and models online (thingiverse has some) of actual working flying wing designs, as well as normal looking tail aircraft designs and even replica full size crafts that are supposed to be flight worthy straight out of the printer. I suppose a first attempt model might make more sense as just a slightly modified (scaled and with space allowed for electronics) version of one of those. I will probably avoid flying wings because of the apparent harder to handle nature of them, and see if I can't just start with something that has already been proven in flight just to save myself the pain of having a poor design.

I hope more people can share their thoughts on this idea - and even if someone could share their experience with parallel wiring designs and what kind of flight times they were able to achieve with simply expanding on batteries.
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Old 12-06-2019, 06:52 PM
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Originally Posted by MD_R View Post
one idea I had is to try to create a long range RC prop plane. I am kind of wondering what I could do with something like an Arduino or Raspberry Pi acting as the brains of the vehicle, and connect to it (perhaps with an FPV camera) over a 4G network, which you can find a few examples of this type of thing online in various places as others have thought of this before me. And with this type of setup I'd probably have a notebook computer with a game controller (xbox) to act as the flight controls of the vehicle - as well as use a simple auto pilot setup on board to allow the vehicle to maintain control if the mobile data connection is lost (what, like a PixHawk?). I understand this is a very complicated setup and certainly not an ideal beginner project
If you are in the USA you need to go to the FAA's website and read part 107 , which your intended non line of sight operations are now governed by .
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Old 12-07-2019, 08:58 AM
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3D printing the major components of model planes is practically all drawbacks and no benefits. Yes, it's been done. But it's not better, easier, or faster.

Before even thinking about the project you want to do, you should learn how planes fly first. The goal you are setting for yourself is something that experienced pilots, Ph.D credentialed professors, and manufacturers with dedicated research teams can't do yet. Start with a properly built off the shelf plane so you can learn how to fly it. No, you can't just skip to autonomous flight so you don't have to learn anything. Autonomous systems aren't foolproof, so you will sometimes have to take manual control. Also, you'll still have to set up your autonomous system, which you can't do if you don't understand basic flight.

Don't try to create your own flight controller. The Pixhawk can do all of the things you are talking about with autonomous control, GPS waypoints set with a laptop and a ground station.

30 miles isn't possible with hobby grade products. 4-5 miles from where you took off is at the outer edge of the range for the radio gear and FPV equipment we have. Most can't get that far away reliably.

On the topic of more batteries for more range- basic flight physics tells us that with more weight we get more drag. With more drag, more power is required to keep flying, which uses up your batteries faster. There is a point when adding battery capacity where you actually reduce your flight time. That break even point depends on a lot of variables, but it's an issue that all aircraft, model and full scale too, have to work around.

I love seeing your ambition and interest in planes and autonomous technology. Understand though that there are steps to getting where you want to be, and they will all cost money and time. An initial investment in a plane like the Hobby King Bixler and a FrSky Taranis radio will let you learn basic piloting, and it's a popular platform for FPV when you are ready. You won't be ready in your first week, probably not in your first month in the hobby. I'm sure there is someone who has set up a Bixler for autonomous flight, but the weight is going to become a problem very quickly on something that small.
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Old 12-07-2019, 12:51 PM
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Originally Posted by init4fun View Post
If you are in the USA you need to go to the FAA's website and read part 107 , which your intended non line of sight operations are now governed by .
I am aware of this - and do not intend to really use it outside of the law, and probably would only do test flights within line of sight like the law allows. It is more the tech I am interested in rather than a real purpose, so I won't be using to fly in ways that are not allowed.

Originally Posted by jester_s1 View Post
3D printing the major components of model planes is practically all drawbacks and no benefits. Yes, it's been done. But it's not better, easier, or faster.
Well while I understand that there are more common and practical materials out there - the 3D printing is really what has my attention not just for this plane idea, but many other things I think would be interesting to try and create with it. Some modern printers create very solid and tough prints, and some materials are relatively light (compared to more common PLA or ABS) although they would likely be heavier still than some other materials like balsa wood.

Originally Posted by jester_s1 View Post
Before even thinking about the project you want to do, you should learn how planes fly first. The goal you are setting for yourself is something that experienced pilots, Ph.D credentialed professors, and manufacturers with dedicated research teams can't do yet. Start with a properly built off the shelf plane so you can learn how to fly it. No, you can't just skip to autonomous flight so you don't have to learn anything. Autonomous systems aren't foolproof, so you will sometimes have to take manual control. Also, you'll still have to set up your autonomous system, which you can't do if you don't understand basic flight.
You make good points here, and yes I do understand there is a good bit of learning I will have to do to get up to speed, or even stand a chance to lift of the ground let alone reach some sort of nice flight range - but that certainly won't stop me from trying.

Originally Posted by jester_s1 View Post
Don't try to create your own flight controller. The Pixhawk can do all of the things you are talking about with autonomous control, GPS waypoints set with a laptop and a ground station.
Yes I wouldn't be trying to create one of my own - I am not good enough to create something like a Pixhawk on my own, and will be relying on pre-created and tested software and hardware entirely, even if I do change a bit of code to fit my application, but again I am experienced with programming and that will likely be the easiest aspect for me to get done.

Originally Posted by jester_s1 View Post
30 miles isn't possible with hobby grade products. 4-5 miles from where you took off is at the outer edge of the range for the radio gear and FPV equipment we have. Most can't get that far away reliably.
This is certainly discouraging. I am aware of the limitations of the 4-5 miles of consumer radio gear - but as far as I could tell there were battery/motor combinations that would provide longer, perhaps slower times in the air. Is that not true?

Originally Posted by jester_s1 View Post
On the topic of more batteries for more range- basic flight physics tells us that with more weight we get more drag. With more drag, more power is required to keep flying, which uses up your batteries faster. There is a point when adding battery capacity where you actually reduce your flight time. That break even point depends on a lot of variables, but it's an issue that all aircraft, model and full scale too, have to work around.
I was hoping with a certain amount of lift, and strength on the motor, I can reach potentially far distances with the parallel batteries - I wonder if going with a custom made battery pack with many high quality cells rather than several consumer packs, if that limit could be pushed?

Originally Posted by jester_s1 View Post
I love seeing your ambition and interest in planes and autonomous technology. Understand though that there are steps to getting where you want to be, and they will all cost money and time. An initial investment in a plane like the Hobby King Bixler and a FrSky Taranis radio will let you learn basic piloting, and it's a popular platform for FPV when you are ready. You won't be ready in your first week, probably not in your first month in the hobby. I'm sure there is someone who has set up a Bixler for autonomous flight, but the weight is going to become a problem very quickly on something that small.
Hmm well while I don't really like the idea of starting with a pre-created body I suppose that may be something to consider especially with the weight of printed materials.

I appreciate all your replies guys, thanks for sharing your insight, even if its not necessarily what I am hoping to hear! :P
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Old 12-07-2019, 07:59 PM
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You might first study the principles of flight, and what actually makes an aircraft fly. There's quite a bit of science that goes into that alone. There's a reason flight times might seem limited in models to some that don't understand even the easiest fundamentals. It's not all about "put a bigger battery in it". There's many principles that prove that. The history of flight would tell you alot about what's worked, and what hasn't and why.

I commend your enthusiasm, but you must walk before you can run. A simple model might shed some light for you. If you can design, and/or build a simple model, or even a kit of some sort, you'd have a grasp on what that aspect alone entails.

Every pioneer in the history of aviation started with models of some kind. Burt Ratan was/is an avid model builder and designer, look where he's at today. Every astronaut has probably been a modeler, as well as most pilots. Some full scale pilots fly RC for fun... many of my RC friends are licensed pilots, some airline pilots... but it all boiled down to building models. That fundamental foundation has helped to form and teach the best designers and pilots the world has ever known.

Yes, there's files and such out now for 3D printed models... I have a friend that's working on a 1/4 scale 3D printed aerobatic plane right now... and he's got alot of experience, and is pretty realistic in what he can and can't do.

I'm not saying what you're after can't be done, long range RC has been done many times... miles and miles.. the military can fly thousands of miles away of course... If you're determined and have the talent and ability to do whatever it is you're posting about, you'll find a way. The best thing you might get is experience in one form or another. Just build something and fly it.. that will give you some experience.
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Old 12-07-2019, 09:32 PM
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As noted, you haven't started on a project that will bear fruit in a short time. But it can be done. The researcher I referred to is just one of us - started with model planes in his late teens. Read, studied, experimented. It was solely his hobby. His real job was various "programmer" type jobs. Now in his late 40's he's got a research position at a major University doing just what you laid out. Custom building planes for long duration autonomous flight. Everything built from scratch except the core radio control transmitter, receiver, servos and propulsion. All of that is from the local hobby shop. The advantages he now has: a)grants from NASA, and a small (4-6 students) number of "assistants" to help on the project. But he got there doing it all on his own as a hobby. He can just now get even more complex. and has a small group to provide more design input, and help get a project in the air in a much shorter time.
The current phase: Program for auto flight, flying a preprogrammed search grid over 100's of acres, while using cameras to search for invasive specie infestations - aphids, ladybugs or various weeds. He pinches himself every day that he gets a great salary, gold healthcare, and a pension, all just for "playing with model airplanes".
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Old 12-08-2019, 01:23 PM
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Since you asked the question again after I had answered it, I'll answer it again: No, adding more batteries won't give you what you want. It doesn't really matter how your battery packs are configured. Capacity costs weight, so whether it's one big pack, several smaller packs, high quality vs. low quality, you won't be able to get 30 miles of flying out of a charge.

Have a look at some of the commercial UAS vehicles. They can do what you are talking about. Lots of development went into them, and they are big and expensive. But maybe this is the start of you working for one of those companies eventually.
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