Propeller size tunning / new 18650b batteries cells

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Propeller size tunning / new 18650b batteries cells

Postby afernan » Fri Dec 21, 2012 12:40 pm

Propeller selection is a difficult matter. In fact is the combination propeller/motors.

I´ve been testing many combinations in AQ, but I´ll report the more effitients, IMHO.

I´m using basically three combinatinons motor/prop all on same Quad mid size (1Kg w/o battery)
conf-1) motor MT2212-16 KV750 & propeller GF 10x4.7
conf-2) motor RCT 5010-14 KV360 & propeller carbon 15x5.5
conf-3) motor RCT 5010-14 KV360 & propeller carbon 16x6.5 (see image below)

Main conclusions I´ve got are the following:

a) Effitiency.
Big increase using large propellers, that is conf-2 is the best. I get almost a 45% more flight time than conf-1 (11 min on conf-1 vs 16 min in conf-2 with a 3S-2200mA). I get also long time flights: 40min+ with a 4S-4000mA in conf-2
Conf-3 not yet tested in flight time, but I thing the pitch is too high (6.5) so not so good, but still TBD

Stability
Large propellers induces instability when moving out with a pulse of PH or RTL. It´s needed to reduce NAV_SPEED IM,OM,PM to 10,15,10 respectively to avoid the divergence (see my post on that also)

Under windy days large prop are much more sensible. Need of tunning. Deffault PIDs are goog for conf-1 but not for larger prop.

Altitude tunning is also needed for larger props. I use NAV_ALT_POS_P = 0.15 and NAV_ALT_SPED_I = 1.85 to avoid up/down jumps.

Others.
- Larger are more expensive
- larger are mor difficult to transport
- larger are easy to brake
... but in a calm day larger props fly soooo well and smoooth that I love it.

Angel
Attachments
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Last edited by afernan on Sun Dec 23, 2012 7:39 pm, edited 1 time in total.
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Re: Propeller size tunning. Tests and reflexions

Postby LPR » Sat Dec 22, 2012 6:20 am

Angel

I ordered the RC Timer 15 x 5.5 and 16 x 5.5 props a week ago for a new quad. I'm shooting for one hour flight time with a 10 oz camera and simple pitch gimbal. Going to try a Panasonic 18650B battery 4s, 2p pack. Should get close to a hour if the frame is light enough.

It will be fun to compare how they perform.

Larry
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opps

Postby LPR » Sat Dec 22, 2012 6:23 am

opps
Last edited by LPR on Sat Dec 22, 2012 6:52 pm, edited 1 time in total.
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Re: Propeller size tunning. Tests and reflexions

Postby bn999 » Sat Dec 22, 2012 3:52 pm

Larry: I managed a 1hr 20min flight using 18650A's in a 5Sx8P configuration using the RCT5010 & 15x5.5 CF props hex layout. It was the first flight I had where the 32bit us timer rolled over :)

The 18650B's should be able to do a little bit better, but in a 2P configuration I think you are going to draw too much current per cell and greatly reduce the total VA that they will deliver.
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Re: Propeller size tunning. Tests and reflexions

Postby afernan » Sat Dec 22, 2012 5:49 pm

Whats are those 18650 batteries?. I don't know that. Where to buy?.
Do they have advantages wrt classical lipo packages ?
Angel
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Re: Propeller size tunning. Tests and reflexions

Postby Max » Sat Dec 22, 2012 6:17 pm

bn999 wrote:I managed a 1hr 20min flight using 18650A's...

:o Just a test to see if you could, or some special mission? For me 15min. seems like a long flight! :)

Angel, 18650 is a size/type of LiIon rechargeable cell. They're pretty common, any decent battery place should carry them, as well as Amazon and others. http://en.wikipedia.org/wiki/List_of_ba ... chargeable

-Max
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Re: Propeller size tunning. Tests and reflexions

Postby LPR » Sat Dec 22, 2012 6:29 pm

I'm trying to find good info on the C rating for 18650Bs. I read they can take anywhere from 1C to 10C but at 8C you have over 50% of the batteries energy going to heat. If I make the frame and pitch only camera gimbal very light weight I think I'll be just a little over 1C draw in hover.
I'll build it and measure the current it take of hover and make the battery that it will take to get over a hour.

An hour and 20 minuets is very,very good. If I could get my hands on Sony's Lithium cobalts, two hours would be next challenge.

Larry
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Re: Propeller size tunning. Tests and reflexions

Postby LPR » Sat Dec 22, 2012 6:44 pm

Angel

Here's a place for the newer Panasonic 18650B with 10% more energy storage than 18650A and can be recharge over 500 times.

http://www.solarcarsupply.com/ocart/ind ... MgodUHEA0Q

The advantage is about 30% more energy per unit weight than lipos. The new "B" cost more and might have a higher C rating. If you don't like very long flights they would not be worth the effort to built a CD welder and assemble a battery pack. Panasonic 18650 battery pack needs to be large so you will have the current potential to fly a quad.
Ebay has 18650As that have tabs so you could just solder them together.
My charger has a setting for lithium ion batteries. They are a little different to charge then a lipo.

Larry
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Re: Propeller size tunning. Tests and reflexions

Postby Max » Sat Dec 22, 2012 7:04 pm

I've never considered LiIon suitable for flight packs due to the low discharge rates, typically 1C or lower before the voltage sags and performance drops. Even with 8P 3.4A at 1C that's "only" 27A. But I guess for a MR that might be OK if you're careful...

Larry, where are you seeing 10C discharge rates for the Bs? I can't find any discharge curves for them. There's a 18650CH hybrid that can supposedly do 10C but those are 2250mAh cells. I've read a few electric bike and Tesla forum posts suggesting the B cells are best at 1/2 C rate, with short higher bursts being OK, but this is just hearsay.

BTW the Panasonics come in "protected" versions which have built-in current limiting... probably not what one would want for a flying machine. Here's another source for individual cells: http://www.orbtronic.com/batteries-char ... -ncr18650b

-Max
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Re: Propeller size tunning. Tests and reflexions

Postby LPR » Sat Dec 22, 2012 8:22 pm

Max

I agree that it's not very reasonable unless you really want long flights or an electric car that can go three hundred miles. The only other way to get long flight times is to use a gas powered Helicopter. An autopilot controlled helicopter is very expensive compared to an AQ with lithium ion battery.
To save weight I could glue the 18650 batteries together and use them for the arms on the quad. :D

I just replaced the battery on my laptop so I lost the page I had minimized and trying to find it in the history would not be easy. The info I think was from a guy that measured the battery at 1-2-5-8 and 10C. He reported the voltage drop which was not bad at 1C but went up quickly with greater load.

Larry
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