Aeronavics / Droidworx Flight Time assistance needed.


I have a question regarding "expected" flight time.

I flew the CX-4 for the first time yesterday and was quite dismayed by the flight time that I was getting before the NAZA Voltage Monitor started its rapid red LED flashing signifying that I had hit the first level of 'protection' at 15.4v. My pack was freshly charged.

My flight time was 90 ~ 120 seconds for each of the 6 flights that I managed between charging the packs. I flew with both packs on the CX for balance, but only one was plugged in for each flight. Flight weight was 2280g.

Droidworx
cx-4 v2
Futaba R6208SB 8-Channel 2.4GHz FASST
Photohigher CX 111 CX 1 Micro Tilt gimbal
AXi 2217/20 Droidworx Edition (840Kv)
Graupner Elektro Prop - 11x5
Propeller hub spacer 8 and 5mm
DJI 30A ESC
DJI NAZA w/GPS
RePlay XD1080 camera

The CX-4 is balanced at mid point (between the skid brackets).

My all-up wieght is 1700g NOT including 2 x Hyperon 2600mAh 4S batteries at 290g each

By comparison, the F450 that I fly with the same 2600 mah pack averages 9 minutes (540 seconds).
The F450 has 920kv motors.
Flying weight w 2600mah = 1096g (5000mah = 1364g)

The only differences that I see are:
1. Weight:
CX = 1700g (no battery)
F450 = 806g (no battery)

2. Motor:
CX = 840Kv (rpm/volt)
F450 = 920Kv (rpm/volt)

3. Blades:
CX = 11/5
F450 = 8/5

Am I missing something? To say that I am incredibly disappointed in the flight time is an understatement. I had planned to fly it with 2 x 2600mah batteries in parrallel for 5200mah capacity and hoped to get a total of 14 ~ 15 minutes of fight time. Based on the actual flight time, I will only get 3 minutes.

Any assistance will be greatly appreciated.

Thanks,
Dale.
 


nicwilke

Active Member
If you are using 4 motors, I think you are over limit (18A) for weight and prop size. You can get around this by getting another 4 motors and replace props with 10x5's. That should bump you closer to 10 mins on your 5000mAh capacity. It will raise AUW a bit with motors and associated setup.
You may get closer to 18/20 minutes with 2x 5000mah with coax and 10 inch props.
 

Can I ask what C rating your batteries are and is the CX coax?

If you are using 4 motors,I think you are over limit (18A) for weight and prop size. You can get around this by getting another 4 motors and replace props with 10x5's. That should bump you closer to 10 mins on your 5000mAh capacity. It will raise AUW a bit with motors and associated setup.
You may get closer to 18/20 minutes with 2x 5000mah with coax and 10 inch props.

Hi nicwilke.
The batteries are 35C. When you state that I am over limit (18A) for weight and prop size - is that for each motor (30A ESC not withstanding)?

I have only fitted 4 motors (not co-axial).

What motor (brand / motor number) would you recommend? I already have 8x5 and 9x5's - *if* these would work, would I necessarily need to go to the 10x5 (I guess I'm wondering about the incremental increase / decrease from the 11x5's that I currently have fitted)?

I also have 5000mah 35C batteries (558g each). How will the added weight trade off to flight time?

Here's what it looks like...

View attachment 10089

Thanks for you help.
Dale.
 

Attachments

  • 20130309_161803.jpg
    20130309_161803.jpg
    141.2 KB · Views: 301

nicwilke

Active Member
Nice looking rig mate. Looks fantastic. I would do a test with 9's today and report back. It really shows the small size of your motors with those props.
If you wanted to upgrade to bigger motors, try the 2814-22's from AXI. They would spin the 11's better.
Let us know how the 9s go
 

Hi Nicwilke -
With longer flight time being the desired result, is there a "formula" - or thinking that will allow me to achieve that result?

i.e why 2814-22 vs 2217-20? How do I determine the best motor / weight / prop size combination?

Thanks!
Dale
 

nicwilke

Active Member
Take a look at www.ecalc.ch and click multicopter part. Fill in the top part. I'll let you see theoretical flight times etc. Let me know if you need assistance, it'll help you choose setup.
 

Razzil

Member
I had several smaller 4s 2250mah batterys in parrallel, ending up using one 4s 6000mah afterwards. All of which from maxamps. I'm getting between 10 to 15 minutes these days, but I could swear I was getting longer at first. maybe because i'm flying a lot faster these days then before, which makes sense.

Regarding you're voltage protection kicking in on the Naza ... i've found that issue with every frame and setup I've ever used with the Naza. I disable it and use a foltage alarm from hobbyking ... when i hear the alarm, I bolt and land as quick as I can. I can almost judge by the timer on the controller. that might not help you much, but thought I'd chim in.

Regarding eCalc ... i could never get that to work, not with the Axi motors plugged in.
Regarding the formula ... this link might help.
 

Take a look at www.ecalc.ch and click multicopter part. Fill in the top part. I'll let you see theoretical flight times etc. Let me know if you need assistance, it'll help you choose setup.

I've fitted the CX4 with 9/5 Graupners - but the winds are pretty steady at 15 with some gusting to 35 so -- I've decided not to test yet. If it calms down a bit this vening I can still get a couple of flights in and see what the actual flight times are vs the eCalc results.

I have added four files. Each one is paired by motor type with both 9/5 and 11/5 props. From this it seems (all other parameters being basically "equal" that the 2814/22 spinning an 11/5 provides the longest flight time (with no warning messages). The one vairable that I was not able to really model was the prop as I use Graupne eProps. For the sake of standard calculations, I used the APC Electric E.

I'll provide flight time when I am able to get in the air again.
Thanks.
Dale.
 

I had several smaller 4s 2250mah batterys in parrallel, ending up using one 4s 6000mah afterwards. All of which from maxamps. I'm getting between 10 to 15 minutes these days, but I could swear I was getting longer at first. maybe because i'm flying a lot faster these days then before, which makes sense.

Regarding you're voltage protection kicking in on the Naza ... i've found that issue with every frame and setup I've ever used with the Naza. I disable it and use a foltage alarm from hobbyking ... when i hear the alarm, I bolt and land as quick as I can. I can almost judge by the timer on the controller. that might not help you much, but thought I'd chim in.

Regarding eCalc ... i could never get that to work, not with the Axi motors plugged in.
Regarding the formula ... this link might help.

Thank you Razzil,
Hearing from someone having some experience with the CX4 - and longer flight times - makes me think that there are some additional contributing factors that I haven't thought through. It seems that our setups are very close to the same .... so I must be missing something that is drawing a lot of power. Not that this should matter, but are you using the Droidworx Power Distro board? Do you mind taking a photo of your setup (under the canopy) and whatever else you might think is useful?

I understand about the NAZA voltage protection being too quick to start flashing. I've adjusted it down to see if I can get some additional flight time that way. I looked at your suggested voltage alarm from HK - but it still uses volts instead of mah used as a method of setting the notification. I may go with the IISI telemetry system and see if I can get a real time readout of what my MR is consuming. I'd like to get 70% usage out of the battery capacity if at all possible.

Thanks.
Dale.
 

nicwilke

Active Member
I've fitted the CX4 with 9/5 Graupners - but the winds are pretty steady at 15 with some gusting to 35 so -- I've decided not to test yet. If it calms down a bit this vening I can still get a couple of flights in and see what the actual flight times are vs the eCalc results.

I have added four files. Each one is paired by motor type with both 9/5 and 11/5 props. From this it seems (all other parameters being basically "equal" that the 2814/22 spinning an 11/5 provides the longest flight time (with no warning messages). The one vairable that I was not able to really model was the prop as I use Graupne eProps. For the sake of standard calculations, I used the APC Electric E.

I'll provide flight time when I am able to get in the air again.
Thanks.
Dale.

I'm building a mini 6 this week and have settled on smaller Graupners as my final props as it's using small motors. I just need to find stock and order them. The Tmotor 2814-10 770kv also do a good job and cheaper than the AXI. I use Avroto and the Tmotor version.
Look forward to your results.



Sent from my GT-I9305T using Tapatalk 2
 

Razzil

Member
I've recenlty picked up a SD Card DVR to record my EzOSD ...
Wind, the next few days is suspose to be between 10 to 15km for several days ... I'll do some recording and post it for you.
 


I've recenlty picked up a SD Card DVR to record my EzOSD ...
Wind, the next few days is suspose to be between 10 to 15km for several days ... I'll do some recording and post it for you.

Razzil,
I'd also be interested in your EzOSD setup? I have one in a box along with some FatSharks that I planned to put into the CX4 once it got sorted.

Thanks.
Dale
 

Razzil

Member
I was going to haul my CX4 apart soon and upgrade it to the v2 platform, so I can take some pictures of all the wiring of the EzOSD setup. Pictures are priceless in a similar setup sometimes.
 

JoshMaxAmps

Member
I understand about the NAZA voltage protection being too quick to start flashing. I've adjusted it down to see if I can get some additional flight time that way. I looked at your suggested voltage alarm from HK - but it still uses volts instead of mah used as a method of setting the notification. I may go with the IISI telemetry system and see if I can get a real time readout of what my MR is consuming. I'd like to get 70% usage out of the battery capacity if at all possible.

Thanks.
Dale.

Dale,

There is a reason that the cutoffs are based on voltage rather than mah. Every lipo battery runs within a window. Lets say this is an 8000Mah pack. The over all amp load is going to determine how much mah you can draw. If you are running a high amp draw flight application the pack will sit under load at a lower voltage than if that was used to power say a light bulb. Here is where the window comes into play. You get to use the mah that is available within the pack until you hit the cutoff voltage. That window is smaller for the higher amp draw applications. Where with the light bulb you will likely see the full 8000mah or maybe even more, the high amp draw application may only see 4000mah in that time frame. This is why running high mah, high C rated packs can be so beneficial as they will hold a higher voltage under load. Providing you with that larger window.

Hope this helps!
 

nicwilke

Active Member
Nicwilke,
Here are the 4 files that I forgot to attach.

View attachment 12997View attachment 12998View attachment 12999View attachment 13000

...oops

Dale.


Dale,
Thanks for sharing. Try a bigger battery pack with the the 2214-22 setup and add the extra weight. I know it's not the motors you are using, but the same happened to me, I sold my original motors to assist in my error of choice. Also try a 5000mah including weight with the current motors too. I think small motors and smaller props would work with double capacity power as is.
 

Ttelmah

Member
Your unit is working well 'outside' the best efficiency area for the motors, but you should still be able to get a lot more time. The first thing to do is calibrate the Naza's voltage sensing. I've had one unit that was OK, and two that 'under-read' the actual battery voltage by a large amount. My DVM (Fluke, calibrated), read 12.5v. My RC telemetry read almost exactly the same, but the Naza read nearly a volt lower. All connected to the same point.
Once I calibrated the sensor on the Naza, the flight times almost doubled.
Then given your high loads, the off-load, and on-load droop may be more than the Naza default settings.
If you have a good charger that tells you how much current is put into the batteries when you charge, you can then carefully adjust the warning point to be at a sensible level. I have mine just over 35% left in the battery, and the 'autoland' at just under 20%.

Best Wishes
 

Your unit is working well 'outside' the best efficiency area for the motors, but you should still be able to get a lot more time. The first thing to do is calibrate the Naza's voltage sensing. I've had one unit that was OK, and two that 'under-read' the actual battery voltage by a large amount. My DVM (Fluke, calibrated), read 12.5v. My RC telemetry read almost exactly the same, but the Naza read nearly a volt lower. All connected to the same point.
Once I calibrated the sensor on the Naza, the flight times almost doubled.
Then given your high loads, the off-load, and on-load droop may be more than the Naza default settings.
If you have a good charger that tells you how much current is put into the batteries when you charge, you can then carefully adjust the warning point to be at a sensible level. I have mine just over 35% left in the battery, and the 'autoland' at just under 20%.

Best Wishes

Based on this, would you suggest that the 2814-22 motor would provide the necessary efficiency to work within the combination of ESC, Motor and 4S battery to lift the weight (understanding that the battery "capacity/mah" will determine flight time)?

Re: your comment about calibrating the NAZA. I am using a Hyperion EOSO606i charger that provides me with a total mah that has been put back into the battery. My battery monitor reads 16.7v (?) fully charged. The NAZA cutoff was set to -0.7v for the first cutoff and -1.4v for the 'auto-land' feature. I have since changed this to -1.4 for the first stage and -2.0 for the 'auto-land'. Note: I have NOT flown it with these changes yet.

Once I have flown with these new settings, I will (should?) be able to calculate the amount that the charger puts back into the battery to see if I am setting the first / auto-land stages correctly. If this thinking is wrong - please advise! I am not sure how else to calibrate the NAZA sensor (the real-time telemetry system such as the IISI unit should provide the same result, just 'real time' insead of reading the result following a full charge cycle).

Dale.
 

Dale,
Thanks for sharing. Try a bigger battery pack with the the 2214-22 setup and add the extra weight. I know it's not the motors you are using, but the same happened to me, I sold my original motors to assist in my error of choice. Also try a 5000mah including weight with the current motors too. I think small motors and smaller props would work with double capacity power as is.

Hi nickwilke -
The CX-4 V2 has two battery holding 'detents' added into the landing gear. I have tried to fly it with the two 5000mah batteries strapped in but had some serious 'harmonic balance' issues (severe in-flight vibration) that I have not experienced with the two 2600mah batteries strapped in. I did fly it with one 5000mah battery between the skids (in the center) with no in-flight vibration.

The weather had not cooperated yet as it rained all day today following the winds from yesterday -- so I still have not been able to try the 9/5 props. I would hate to have to break this thing down and replace the motors, but 90 second flights are not acceptable to me.

I'm ready to go once the weather breaks!

Dale.
 

Top