(30-Jan-2021, 11:28 AM)hugnosed_bat Wrote: tiny reallife try today, haha what a result xD
7degrees outside

started with the liion, in case i wont fly after... 24seconds tha battery passes 3.5v. another 25s the voltage passes 3v. the liion doesnt provide nearly the c-rate in cold conditions, this let me believe even in warm conditions the battery wont be able to provide the capacity bevor voltage drops under 2,5v per cell.
i believe liion with their low power is the wrong battery for this settup. 2s2p 6000mah would make the battery way to heavy, need that 70g liion xD doesnt exist :-)

i flew 11miutes on the 1500mah battery, the voltage recovered to 3,6v per cell, lets see what mah it used by recharge :-)

i had spare transmitter battery, 900mah 2s 25c, i flew 4minutes until it started to rain. there was still capacity and no drop under 3.3v

both flights was with a few powerless flips and rolls, sort of cruising and mixed flights.

What Li-ion cells were you using? I think having good high-current cells is critical to prevent that severe voltage sag you were seeing. The cold certainly doesn't help, but I'm glad you had a decent flight with the Lipo! 

My guess is efficiency will got down with the GF4023 compared to the GF5125.

(30-Jan-2021, 12:58 PM)romangpro Wrote: You need to look at it from power/watts and efficiency perspective.

Typical 600g 5" 6S, slow crusing is only 4.5g/W.
If you use 4S, or small battery goes up to 5g/W. Maybe 6g/W. On oldschool 5", 15min flight time is almost impossible.

But talking ultralight.
We have 250g limit. Assume 400g thrust cruising.
So, find best motor + prop @100g thrust.
Sunnysky 2304 is 20g and can do 13.5g/W on 8043 prop.
https://sunnyskyusa.com/collections/prem...y-x2304-v3

400g thrust, 250g hover (eff even higher, so W lower)
@10g/W = 40W, 25W*
@13.5g/W = 33W, 19W*
Our power use should be somewhere in this range.

The hyper efficient 2304 motors and 8" prop. 13.5g/W.
A Gaoneng 1100mah HV 4S = 800Wmin @80% capacity.
800/33 = 24min cruising and 800/19= 42min hover

But, we cant build a 8" under 250g, and this battery.
But if 5", we hit 10g/W:  800/40= 20min cruising, and 800/25= 32min hover. I think thats realistic

I think that's certainly true, but the thrust tables most manufacturers publish are idealized at best (and completely misleading at worst). I don't think you can actually expect to see anywhere near those numbers in practice, making it hard to rely on them to predict performance. 

You can pretty accurately model motor and prop performance from a few parameters, however, and these are easily measured for brushless motors. From the motor resistance and idle current you can calculate an efficiency curve for the motor and figure out the current draw at max efficiency. From there it's a matter of finding an efficient prop that will provide a good cruise speed  (ie thrust) in that power range. Probably much easier said than done

I have couple 4" builds.
I tried both 4023*3 and 4032*3 to compare T4025.
The triblade significantly less efficient.

But, on my 5inchers, I compared T5030 and T5125, and almost exactly same. Even 5040*2 and 5040*3 where close.

But, this is just OSD Watt reading hovering and 30kph very slow circles.

(31-Jan-2021, 02:27 AM)V-22 Wrote: I think that's certainly true, but the thrust tables most manufacturers publish are idealized at best (and completely misleading at worst). I don't think you can actually expect to see anywhere near those numbers in practice, making it hard to rely on them to predict performance. 

You can pretty accurately model motor and prop performance from a few parameters, however, and these are easily measured for brushless motors. From the motor resistance and idle current you can calculate an efficiency curve for the motor and figure out the current draw at max efficiency. From there it's a matter of finding an efficient prop that will provide a good cruise speed  (ie thrust) in that power range. Probably much easier said than done

Mfcr tables have outliers. If some value is great only on one prop or voltage, its probably typo/mistake. Or even they put 1206 motor thrust instead of 1204 - mr iflight.

Oldschool 2204-2306-2207 can do 4.5g/W up to 6g/W @100g thrust. Yes, eff is lost due to aero, PID, vtx etc. But its usually close.

Sadly, we dont have any independent expert doing proper motor testing. Well, one guy on facebook group using dyno.

https://batterybro.com/products/samsung-...00mah-5-2a
this is the liion cells i own, 2600mah able to provide 5,2a continious... to low for my setttup
i will try better cells on it tomorrow :-)



on emax avan 4023 (4123 or something in truth)
hoover throttle is pretty on the same throttle level, probably the 1306 was still way to overproped by the gf5125?!?

(31-Jan-2021, 01:31 PM)hugnosed_bat Wrote: https://batterybro.com/products/samsung-...00mah-5-2a
this is the liion cells i own, 2600mah able to provide 5,2a continious... to low for my setttup  
i will try better cells on it tomorrow :-)



on emax avan 4023 (4123 or something in truth)
hoover throttle is pretty on the same throttle level, probably the 1306 was still way to overproped by the gf5125?!?

Yeah, those Li-ions would barely get you off the ground :
If you're going the Li-ion route, I'd highly recommend some genuine Sony VTC6 cells. RDQ has them for a good price:
https://www.racedayquads.com/products/so...-diy-packs
They can actually deliver useful currents, continuously, without too much sag. If you fly conservatively those Samsung 30Q cells you mentioned also having might be ok, but any high current maneuvers are going to hit the current limit. The VTC6 can deliver the 50A max current your quad will draw in short bursts, and will give you a much more enjoyable flying experience. 

If you order the VTC6 from RDQ, order some of those APC props while you're at it! Should be a pretty amazing combo.

+1 for VTC6.. if you are doing li-ion.
also, do throttle limit and throttle curve

i could hoover nicely indoors with these low-c liion cells, a bit strange how the difference was outside

i ttied the 4inch props yesterday on the 1500mah 2s. i couldnt resist, did that slow acro with low throttle authority xD i got 7min under high throttlelevel.

as i like performance, i wont by high quality liion, but i will try some from my buddies.

overall it let me mention about the hyperbola, i got 19min very slow flighttime on a 4s 1000mah. a powerfull ultralight seems more efficiency on a low throttle level.
it could carry heavy batteries, two times the 2s 1500mah..
i have another ul with 1806 engines, it provided 5min high throttle flights on 4inch, awesome perfomrance on 5inch blades for 2,5minutes. even ghis should give more flighttime. one rare moment when i was try to get range, as much as my xm+ let me do until a failsafe risk, there was a lot spare capacity. i was about 800m outthere and i could do it twice, i even got a relativ high speed about 50kph. 800 plus returning 1600m, x2 = 3,2km, this was on high pitched 5051 props, i believe 3.2 would be easy possible.
i believe i will try a few things and than let this try rest in peace xD

the 1306 are realy overused motors, they wont provide their normal performance about efficiency... not the best try thisway...

im on the way to a buddy which has a few apc blades, probably i can grab a set and some higher quality liion for a try :-) but its raining :-(

Hi V-22,

In your opinion, the Sony VTC6 3000 mAh Li-Ion batteries are better than the Samsung 18650 3000 mAh Li-Ion batteries, correct ??

I have added the VTC6 to my wish list at RDQ. Next order, I will pick some up.

Thanks.

Hi Hugnosed,

Since you like performance, why would you use Li-Ion ?? From what I can tell, the LiPo batteries are much better for performance.

Samsung makes a ton of different 18650 cells, but the Sony VTC6 are easily the best 18650 cells from a capacity/discharge perspective I've found so far.

The higher C-rating of LiPos certainly helps performance on most quads, but those built for LR efficiency tend to have lower current requirements. Plugging hugnosed's quad specs into eCalc gives a max expected current draw of 50A, which the VTC6 can easily deliver in short bursts. Even at full throttle, you'd expect the current draw to decrease over time as the quad accelerates and the props unload (assuming flying in a straight line). Li-ions are going to struggle with acro, when the props rarely unload and current draws remain high.

i like to experiment, thats the only reason i builded the quad. so because of that i wont buy liion cells by myself.
but this experiment are at the limit of my endurance :-)

my buddy had some brandnew, 40a rated liion cells (i guess they was sony?) we didnt made a 2s pack out of it.
it stopped today by other liion cells, they droped fast to 3v, recovered to 3.15 and hold that 10min, the quad falls out of the sky and died this way. never had that, i can trigger the all 4 esc to initialize by the armswitch xD one of the motors heated up instantly xD i wasnt able to go for my goal long flighttime but it was fun anyway :-)

if i will give liion another try on a new settup, i will choose 3s1p liion or a board able to handle 1-2s on a 2sliion, i dont know a board able for that.

back to my main focus, back to lipos, back to performance :-)

I thought about doing 18650 pack many many timee.
Each time I dont.
You certainly cant do crazy stunts on Li-ion.

From my ebike project I have:
LG MJ1
LG HG2 << less sag
Sanyo GA << less sag
Samsung 30Q
Panasonic 34B
(otherse....)

Highest/best is 20A rated 3000mah.. but practically stay under 10A. Sony VCT6

18650 would work perfectly on HUGE 15" Daya550 quad. 100g motors. I use 14" CF props. Its 15 to 20g/W. On 22V, like 5-6A total. Pretty fast and 10A.

On a 4" or 5" ultralight, you can only do 2S or 3S.
There is no way to do 2P... 6 cells = 300g!

On the 1kg+ beast, 600g battery is normal. Can easily do 2P6S or ,3P4S.

18650 = slow flying.