Oct 29, 2013, 07:59 AM
WiteRabbit
Tavsanist's Avatar
Woow Ferdinand, What a patient. Amazing

i just want to add some dependent variable you talk about, Energy density and Motor RPM dependent on Voltage.
This is why the mB vanish, Also efficiency calibraiton, even if a researcher works experimental. Calculating the efficieny without calibration takes 4 day with ANSYS/CFD .
Calibration is an integral of the all errors of the elemental equations.
Look for System's tree chart.
if energy density is changed, this effect the hover rpm,but not optimal battery.

T: Desired Thrust
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Oct 29, 2013, 10:40 AM
Registered User

For Sale: Tiger Motor U8's 100kv


Hello, I have 12 brand new Tiger Motor U8's 100kv for sale is anyone is interested. I bought a bunch for some other projects and don't have enough time to get to them.

$260 shipped in North America ($20 savings per motor)

Send me a private message if interested.

Thanks, Jason
Oct 29, 2013, 11:33 AM
Registered User
ok back again (thank you for your patience!)

I am a convert,. after some pen and paper maths (my kind of maths) I have moved camps and agree that energy density has no impact on optimal battery (and Ferdinand yes I know why your optimum battery formula is set equal to 0 - some people are not as quick as others)

anyway - bare with me some more (if you care to!) I came up with a graph just so I could work through some numbers (pen+paper)



and then did some sums

1kg quad (no battery)
using relative energy density of 1kg 10v battery having 10Ah

using a graph (above) 200g thrust per motor at 10gw and 1000g thrust per motor at 2gw

1.5kg AUW (375g per motor at 8.25g/w) is 182w or 18.2A to hover,. at 5Ah flight time 16.5mins
2kg AUW (500g per motor at 7g/w) is 286w or 28.6A to hover,. 10Ah flight time 21mins
2.5kg AUW (625g per motor at 6.75g/w) is 370w or 37A to hover,. 15Ah flight time 24mins
3kg AUW (750g per motor at 4.5g/w) is 667w or 66.7A to hover,. 20Ah flight time 18mins

now same but with a higher energy density

1kg 10v battery instead is 20Ah

1.5kg AUW (375g per motor at 8.25g/w) is 182w or 18.2A to hover,. at 10Ah flight time 33mins
2kg AUW (500g per motor at 7g/w) is 286w or 28.6A to hover,. 20Ah flight time 42mins
2.5kg AUW (625g per motor at 6.75g/w) is 370w or 37A to hover,. 30Ah flight time 48mins
3kg AUW (750g per motor at 4.5g/w) is 667w or 66.7A to hover,. 40Ah flight time 34mins

As we can see and without doing further sums they essentially follow the same curve (surprising for me!)

so given that it's not the energy density of the battery that tells us what weight of battery we should use how can we tell by looking at the g/w thrust curve what weight of battery will give us most flight time (other than doing lots of sums)?
Oct 29, 2013, 11:55 AM
5th
5th
Mediocre Pilot Extraordinaire
5th's Avatar
So the upshot is that the optimum battery weight does not change for a given MR regardless of energy density, but total flight time does increase with energy density. So the goal is to find the most energy dense battery at the ideal weight. Works for me.
Oct 29, 2013, 12:46 PM
Registered User
Quote:
Originally Posted by EndOfDays View Post
Seems that is it quite "en vogue" to "ditch out" the Naza, but this is easy without offering alternatives.

The only boards (without GPS) more lightweight are the KK-boards, the KK2.0 and the MWii, but I can tell you that you will feel pretty exhausted when you were flying more than 1h without a proper baro (there are not that many FCs with a proper baro). The Naza is 34gr (without the PMU, can be powered by a ESC-bec).
OpenPilot Revolution?
14g with antenna
And the GPS board 10.7g
Oct 29, 2013, 01:11 PM
Registered User
chuenwe's Avatar
Quote:
Originally Posted by AGS2 View Post
Quote from the site:

Status
(info) While the Revolution is currently a very capable flight controller, it is not yet a fully polished turnkey product. It is part of an Open Source community development effort and that is what really makes joining the Revolution exciting. There is a lot of interesting and challenging code left to write on the software side, there is also a lot of testing that needs to be performed, as well.
This community involvement is a big part of the OpenPilot project. We need you to get involved! (on the forum and the wiki). However, if you are an end user just looking to simply get in the air as fast as possible, the Revolution may not be for you at this time.
Oct 30, 2013, 09:58 AM
Registered User
NeoStorm1x's Avatar
Been lurking here for a while love the arguing & debating, And wanted to say thank you to Eod for the original post im sure alot of us are getting much better flight times than before.

Oct 30, 2013, 10:26 AM
Full Scale Piper Cub Driver
Piper J3's Avatar
Pardon the intrusion, but I find this thread very interesting. I did a quick search and didn’t find an answer so I will pose a question… Is it possible to drop a battery in-flight when it is used up? Perhaps several batteries on-board and as one is consumed it could be dropped to lighten the payload. This is not too different from how a jumbo jet climbs to altitude in stages where higher altitude is only attainable when fuel load is burned off. I will return to the sidelines.
Oct 30, 2013, 10:46 AM
Registered User
blacksto's Avatar
Quote:
Originally Posted by Piper J3 View Post
Pardon the intrusion, but I find this thread very interesting. I did a quick search and didn’t find an answer so I will pose a question… Is it possible to drop a battery in-flight when it is used up? Perhaps several batteries on-board and as one is consumed it could be dropped to lighten the payload. This is not too different from how a jumbo jet climbs to altitude in stages where higher altitude is only attainable when fuel load is burned off. I will return to the sidelines.
Pardon me, but I don't think dropping a battery in flight could be a very good idea. Remember that battery damage could occur and you may destroy a good LiPo / you could hit somebody or something. If you are thinking about including a parachute for each battery - still not a good idea. Parachute is plus weight. And does not always deploy. From my point of view. Thanks.
Personally I am always wondering where are those fuel cells promised?
Oct 30, 2013, 10:53 AM
Youtube: TomRi25
Dr.Tom's Avatar
you would need to deplete first battery totaly,
then in-flight switch to another, full one, with higher voltage,
then drop the used one... safely in someones hands preferably, since they don't come cheap

switching is tricky because you want to avoid shorting empty and full batteries together (high current would flow to empty one and could damage it)
also ESC's could act funny if FC sends them PWM needed for RPM for hover at 12V and then next moment they have 16V and same PWM,


here's my LiIon 4S4P just like EOD's from first post,
quad soon in the air i hope


Sincerely,
Tom
http://www.tinyurl.com/drtomyubito
Last edited by Dr.Tom; Nov 03, 2013 at 10:15 AM.
Oct 30, 2013, 11:42 AM
Registered User
Quote:
Originally Posted by 5ilver View Post
so given that it's not the energy density of the battery that tells us what weight of battery we should use how can we tell by looking at the g/w thrust curve what weight of battery will give us most flight time (other than doing lots of sums)?
Plot the following formula vs the Thrust for your motor/prop combo, assuming x is the weight of the quad without battery, thrust and efficiency from motor/prop tests (you will get a plot similar to the one in the attachment):

(1 - x / (thrust*4)) * efficiency

In the curve you get establish the highest value (taking into account the max throttle you want to hover at). Your optimal battery weight will be (Thrust*4 - x) at that point.

Cheers,

jams

P.S. just to add - for most regular quads this will be the point at exactly the amount of thrust you choose for hover. For example - if you want to hover at <50% throttle for most quads the optimal battery will be the maximum battery that will enable you to hover at 50%
Last edited by TheJams; Oct 30, 2013 at 12:41 PM.
Oct 30, 2013, 04:32 PM
Registered User
You can try also NAZE32 from Timecop (Abusemark.com), it'a very small (same size of openpilot) and weight less than 6 gr.
I like it best with latest Harakiri firmware (a fork from the original baseflight) from Crashpilot1000, that adds lot of features.

The altitude hold is perfect with little or no tuning at all, even on large and light machines. To add position hold you need external gps, and it still needs a bit of work, but it's usable in a proper place.
Oct 30, 2013, 11:43 PM
Registered User
EddieWeeks's Avatar

Question


Quick question...

My setup

6 x 5010 530kv with 15x5.5 carbon props...
APM 2.5
2 x 5000 4S
just plywood and carbon tubes
11.9 g/w at hover at 15 amps..
Super Quite in hover

Flies Great... 40min

Does not Alt hold because all flying is done at 30-40 %
If %60 or more power is applied to any motor.... It coggs out...
( jams up, get out of sync with the ESC, what ever you call it...)

I tried recalibrating the ESCs to a large scale ... not much help.... I changed some parm
in APM software to limit max PW to ch 1-6 to 1600ms... but it did not redraw the line...

This must be a common problem with these 17" props you all are using.... or is the kv on my motors too high or the cell count too high... ?

Thanks...
Oct 31, 2013, 12:05 AM
Registered User
chuenwe's Avatar
What kind of "common" problem with these 17" prop you are talking about? I have no problem with mine regardless of what my throttle is at.

Stretched Talon 750 under 26 mph wind gust (3 min 13 sec)
Oct 31, 2013, 12:40 AM
Registered User
EddieWeeks's Avatar
Quote:
Originally Posted by chuenwe View Post
What kind of "common" problem with these 17" prop you are talking about? I have no problem with mine regardless of what my throttle is at.
What cell count are you running.. ?
What KV are you running... ?

Eddie


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