Fixed Wing Battery Advice Requested

laddlab

New member
Hi guys, researcher at Texas A&M here. I was hoping to get advice on a battery canundrum I was having.

I have two craft. An 1800mm wingspan 11.7" single prop Sonicmodel Skyhunter and 900 frame hex copter. I am set on buying maxamps batteries since I will be flying expensive equipment on remote islands and over water. The plane takes 3-4s and the hexcopter requires 6s. Both ideally will use 16k mah batteries, so.....

Considering the high battery costs and then quality chargers for them I was thinking of buying multiple 3s 16k batteries that can be used on both craft with hex being in series.

I understand the loss in RPMs but I know a 3s on a large prop can actually have more grab and the weight savings on the plane is ideal, where the marginal parallel weight increase is fine for the hex. Considering all the factors am I thinking ok or is the 4s much more ideal and therefore need to spend more money diversifying batteries to 6s 16k and 4s 12k (weight saving mah reduction at 4s)

I only care to fly slow and survey but need to be able to battle wind.

I was hoping to buy 4 3s rather than 2 4s and 2 6s, saving me just over $400 plus making all batteries available for each device and longer flight times. Diferrent drones have different uses and arent used in tandem.
 
Last edited:

PsyBorg

Wake up! Time to fly!
Not enough information to say mate. What are the motors and esc's in each craft, what is the weight of any payloads you plan to carry and what all up weight are your aiming for? What props are being used and how long do you need to be in the air?
 

quorneng

Master member
If you can fly the Skyhunter adequately on a 3s then what you propose is logical but the only way to be sure is to try it and see.
With the same prop and motor a 3s will only give you about 50% of the max Watts power you would get from a 4s although the saving in battery weight will counter a small part of that. You could try a bigger prop when using 3s providing the motor and ESC can handle the extra amps.
It will all depend on how you want to fly.
 

laddlab

New member
Not enough information to say mate. What are the motors and esc's in each craft, what is the weight of any payloads you plan to carry and what all up weight are your aiming for? What props are being used and how long do you need to be in the air?

Plane Specs:

Motor: 2820 920KV
ESC: 60A w/5.5v 4A BEC
Servos: 3pcs 12g metal(2 Aileron, 1 Elevator)
Propeller: 11*7
Max 3.5kg flying weight advertising more than 100 minutes flying time

payload is only RASPI, flight controller, battery and FLIR boson.

the primary flight mode is preprogrammed paths through mission planner at 100m altitude tops and hardly any manual flight

the goal is purely research and no personal flying in winds up to 30mph max
 
Last edited:

laddlab

New member
If you can fly the Skyhunter adequately on a 3s then what you propose is logical but the only way to be sure is to try it and see.
With the same prop and motor a 3s will only give you about 50% of the max Watts power you would get from a 4s although the saving in battery weight will counter a small part of that. You could try a bigger prop when using 3s providing the motor and ESC can handle the extra amps.
It will all depend on how you want to fly.

thanks quorneng. that is what I am afraid of. my research budget is quite small and batteries are my first non-sponsored item I must pay for. I may buy a cheaper turnigy for testing before I settle on my more expensive maxamps configuration.
 

PsyBorg

Wake up! Time to fly!
Ok so standard issue store bought gear. Same with the Hexa copter. I will assume its the DJI s900 since you list zero information on that.

You can go the twin 3s in series on both of those aircraft. Many in fact do do that like you said for more diversity for their battery use in different models. the plane will definitely have better efficiency but will only slow down so much without falling out of the sky. The Hexa copter can be speedy but sucks amps fast that way but can be slower and carry better camera gear or other heavier payloads.

As for batteries there is a lot of personal preference as well as hype around their performance. personally I have tried many of the big name expensive batteries and smoked most of them in short time the way I fly pushing for max speed or constant high amp draw pylon style racing. Over my now 6 years flying multirotor I have found the white labeled China Hobbyline the most stable and resilient. I flew a Tatu battery and that changed its chemistry by the third cycle even after a light load break in like I do all my new batteries. The Turnigy and Lumenieer graphene batteries held better chemically and more stable as far as sag but both puffed in short time periods.

The 100c white label CHnL batteries I run have well over 100 hard cycles on them some are over 2 years old with uncountable cycles. I regularly check temps as they charge and discharge as well as the internal resistance and they have only changed slightly from new. I only had one pop a middle cell on its 3rd or 4th flight which they replaced no questions asked when I emailed them the happening as well as starting IR and ending IR.

I run 4s and 5s with the CHnL in 1500 mah and 1300 mah sizes which are common to 5 inch performance quads. They are usually cheaper then the big names and can frequently be found in value packs of 2 or 3 batteries at a discount.

this is what I do to my batteries... 90 to 100ish constant amps with 150 amp spikes if I tap a flag or land with airmode on and they take it with zero issues.

 

Merv

Site Moderator
Staff member
You should be fine to run 3S on the plane & 6s (2-3S in series) on the hex.
Battery slowly lose capacity as they age. Be carful to keep batteries that are of similar age together. Don’t run a new battery is series with one that is a year old.
 

laddlab

New member
Ok so standard issue store bought gear. Same with the Hexa copter. I will assume its the DJI s900 since you list zero information on that.

Sorry, I was on my way into some midterms and did not have time to complete the post. I attached an image of this hexacopter. It was gifted to my project by fta-uas.com so not sure how much of it is stock, but the motors say DJI 4114 pro.

You can go the twin 3s in series on both of those aircraft.

This is def. not true. The plane is limited to 4s and for single prop makes no sense to go over that and rebuy parts. The hexacopter sure can.

My main concern is the flight performance of the plane at 3s. If more experienced pilots/engineers than myself feel 3s can handle basic survey flights in 30mph wind on a bigger craft like this then my preference is to buy several 16k 3s batteries to make the batteries more universal.

To boil it down:

Can the skyhunter reasonably manage in 3s and (with consideration for proper battery pairing) will 2 series 3s have any adverse effects I cannot think of.

or

are the benefits not worth the potential consequences which means I need to pony up and buy optimal batteries dedicated to each respective configuration.
 

Attachments

  • 900.jpg
    900.jpg
    2.5 MB · Views: 0

laddlab

New member
the plane will definitely have better efficiency but will only slow down so much without falling out of the sky.

What were you implying with this statement. That 4s is obviously more efficient or was this in response to the statement that 3s and a larger prop will grab air better and therefore reasonably fly just fine.
 

laddlab

New member
If you can fly the Skyhunter adequately on a 3s then what you propose is logical but the only way to be sure is to try it and see.
With the same prop and motor a 3s will only give you about 50% of the max Watts power you would get from a 4s although the saving in battery weight will counter a small part of that. You could try a bigger prop when using 3s providing the motor and ESC can handle the extra amps.
It will all depend on how you want to fly.

The configuration is rated for 3-4s so either are compatible with the motor and ESC, but you are saying what I feared. I am going to have to spend money to find out for myself. I appreciate the thoughts and input. I am a lowly budding engineer and biologist just trying to make a difference best I can.
 

PsyBorg

Wake up! Time to fly!
Sorry mis typed... The plane can use two 3s in parallel to give longer flight times while the multi rotor uses them in series for the higher voltage.

My confusion is if you want 16k mah per pack or total between a pair of packs. in any case 2x 16000 mah packs is gonna be a TON of weight to haul around.

Anyways Im gonna back away from this as too many variables and unknowns what you are doing for me to give opinions that would be safe and effective. Good luck.
 

laddlab

New member
Anyways Im gonna back away from this as too many variables and unknowns what you are doing for me to give opinions that would be safe and effective. Good luck.

I appreciate all the input for sure. On the plane I would use one 3s 16k battery at a time for 3 cell 16kmah. for the hexacopter I would use two 3s in series to make the 6s required.

In short with 4 batteries I could get 4 plane flights or 2 hexacopter flights.
 

Merv

Site Moderator
Staff member
I appreciate all the input for sure. On the plane I would use one 3s 16k battery at a time for 3 cell 16kmah. for the hexacopter I would use two 3s in series to make the 6s required.

In short with 4 batteries I could get 4 plane flights or 2 hexacopter flights.
The flight time on 3s battery will be shorter than it would have been on 4s. It will just have 25% less energy.
 

laddlab

New member
The flight time on 3s battery will be shorter than it would have been on 4s. It will just have 25% less energy.


"His flight was pretty erratic and hard to follow, but only a portion of it was due to the wind.. that's just how Merv flies! "

Thought that was funny. Thanks for the post. I think I have realized that neither eCalc or forums will get me the exact answer only testing will provide. I feel the loss of energy on a large wing flying long and straight will be partially offset by the weight reduction and as a tradeoff will let me fly a little bit slower so my machine learning can do its processing. I so badly need a mentor/advisor but must forge on.

eCalc has been a convoluted nightmare and I am just too noob for my scientific needs. I am afraid my lessons are going to be reinforced through the pocketbook on this project.

I look forward to racking your guys brains as I embark on this scary endeavor. Our project is sponsored by FLIR, CubePilot.org and many others so I have thousands of dollars of equipment and have never flown a UAV once, but someone must save the sea turtles...
 
Last edited:

quorneng

Master member
laddlab
I note from this Banggood web site that although it suggests the plane can use 3 or 4s the 'normal' specification suggests a 5 to 15 Ah 4s battery.
This rather indicates that when using a 3s battery the lower power it provides that it should be from the lower end of that capacity range and possibly with a reduced payload. You are proposing to use a 3s battery with a capacity (and thus weight) that is just over the top of the recommended range.

You really are going to have to experiment to find out what you can and cannot do using the standard motor and prop with a 3s battery from both a performance and payload point of view.
I would suggest starting with the smallest battery recommendation a 5000 mAh 3s.
 

laddlab

New member
I would suggest starting with the smallest battery recommendation a 5000 mAh 3s

Thanks for the advise and warning. It is def. buzzing around my head. What you say makes good sense and I purchased two 8k mah 3s batteries from hobbyking for testing the 3s functionality. I will use a single then join them in parallel to test full weight.

I have researched a lot on the platform and there are people running some giant batteries (up to 20k mah) but even if we look at the recommended 15k.. The closest I can find is 16k and a 16k hobbyking 4s weighs 1366g.

I am actually wanting to use the 17k 3s from maxamps.com which only weights 977g. All that to say there is so much relativity when they make a recommended battery based on mah and not explicitly weight. Even if I go to 4s 17k mah with maxamps my weight is still equal to any other manufacturers 15k mah at 1294g. All said I think I have considered this but AM worried about pushing it. My research goals are to get the 100km flight distance advertised on the skyhunter adn this is my only reason for trying to tap into the biggest... on top of the ability to reuse on the hexacopter.

Take this with a grain of salt but... I work with a few department of defense contractors and they says maxamp batteries are superior in performace and weight by a large margin and are the only battery maker that can truly handle the c rating advertised on the plastic. Again that is third party advice regardless of the source, but the weight specs alone support at least part of the claim.

Maxamps has a solid warranty and refund policy to match the claims but they assure me the advertised weights are not only accurate but include the weight of the cable or my money back.

My full payload is battery, thermal core (tiny boson), motor, fly color esc+bec, AIDA HDMI cam, Cube Orange, raspi-4 and, here+ 3, herelink+ transmitter.

I expect to be well below the flight weight requirements
 

leaded50

Legendary member
also, you need see what weight the plane have.... (not given) rec. total is 3500g.... shipped kit in box is 3987g ...
 

quorneng

Master member
Unless you have some previous experience in 'endurance' flying I would suggest you consider your 100k goal as a goal and build up to it slowly. Flying a plane with battery weighs approaching 100% of the airframe weight needs care and attention not least of which is the effect on its crash resistance!
 

laddlab

New member
Unless you have some previous experience in 'endurance' flying I would suggest you consider your 100k goal as a goal and build up to it slowly. Flying a plane with battery weighs approaching 100% of the airframe weight needs care and attention not least of which is the effect on its crash resistance!

absolutely. starting with 8k 3s mah flight testes, then two 8k 3s in parallel.

the distance is indeed a long term goal.