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Old Sep 23, 2009, 02:51 PM
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Hi.

If you ganna make 11S2P I'm afraid you will ruin your lipo's.

I don't think it is wise to make 2P with different capacity of the lipo, the 3350 wil be empty before the 3800, this means the 3800 try to charge the 3350 and that's an bad idea!

Just a small warning, I hope I'm wrong but not sure.
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Old Sep 23, 2009, 03:26 PM
Gilbert, AZ
chalmrast's Avatar
Gilbert, AZ
Joined May 2007
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Quote:
Originally Posted by joenella
Hi.

If you ganna make 11S2P I'm afraid you will ruin your lipo's.

I don't think it is wise to make 2P with different capacity of the lipo, the 3350 wil be empty before the 3800, this means the 3800 try to charge the 3350 and that's an bad idea!

Just a small warning, I hope I'm wrong but not sure.
I think you are misunderstanding his setup. He is using the two different capacities in parrallel to make a larger capacity 6S pack. He is then doing the same to make the larger capacity 5S pack. Both 5S & 6S packs will be 7150mAh. He is then hooking these two identical-capacity packs together in series to make an 11S-7150mAh battery.
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Old Sep 23, 2009, 03:39 PM
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Pontus Claesson's Avatar
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Paralleling different capacities....

Quote:
Originally Posted by joenella
Hi.

If you ganna make 11S2P I'm afraid you will ruin your lipo's.

I don't think it is wise to make 2P with different capacity of the lipo, the 3350 wil be empty before the 3800, this means the 3800 try to charge the 3350 and that's an bad idea!

Just a small warning, I hope I'm wrong but not sure.
Thank you for your concern joenella!

In fact, there is no, or very small risk, with connecting and using different capacities in parallel as long as it is the same type of cells (chemistry, brand, age etc).
Another precaution is to see to that all cells/packs get reasonable equal cooling.

What happens when paralleling is that the cells are forced to have the same voltage.
Because of that, they will each charge/discharge at the same C-rate too.

The small risk is if the Ri of the different cells sizes are very far away of being proportional to their capacity.
If a very high continuous C-rate discharge is applied
and the lower capacity cell also happens to have the lowest
Ri, it will deliver more amps. However, in practical use, there are 2 mechanisms that compensate for this potential problem:

1. In almost all cases, there are very varying loads on the battery during a fligh. In low C passes, the parallel cells will balance out.

2. As both Ri and cell voltage drops during discharge, the cell that eventually has lost a little more capacity will deliver less amps until balance is restored.

I will always keep all cells groups parallel over the balancing connectors of course.
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Old Sep 23, 2009, 03:45 PM
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config

...
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Old Sep 30, 2009, 07:39 AM
WATTSUP.SE
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Very nice build Pontus, good to see you have come such long way already, cant whait to see this bird in action!
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Old Oct 04, 2009, 02:24 PM
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Motor fitting

Some more progress on the motor mount, see picture texts.
Sorry for the poor image quality, again I only had my phone camera at hand...

Weight of the cowl as it is right now is 460 gr. So I have added 190 gr and will need 4 pcs 25 mm long stand off's to final the motor mounting.
The 375 gr of motor dome is not needed any longer. If I had used it, I've had to add about 150 mm long stand off's or so.
I think the weight saving is well over 200 gr.
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Last edited by Pontus Claesson; Oct 04, 2009 at 02:51 PM. Reason: Adding weight info
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Old Oct 05, 2009, 08:08 AM
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Strength of motor mount

Have made a calculation of what kind of forces or moment loads that will appear on the motor mount at extreme manouvers like full power snaps etc. Found out that a bending moment of up to 10 Nm is definitely a level that should be possible to resist (prefferable with a good margin)

Anyone that have some rule of thumb about this?
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Old Oct 15, 2009, 06:54 PM
Team Park Pilot - Airborne
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Joined Nov 2006
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Pontus - This is a really fantastic aircraft. I am realy keen to watch the progress. Its always a really pleasure to watch a GS Elrectric take shape by someone who knows what there doing. Best of luck from us Australian GS flyers !!
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Old Oct 16, 2009, 10:02 AM
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...

Thank you BingWing!

The build is ongoing but at the moment mostly the more main stream activties like servo installtion etc. Waiting for some parts needed for the battery installation, then there will be more posts and pictures again, stay tunded!
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Old Oct 18, 2009, 06:17 PM
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will do !
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Old Dec 07, 2009, 01:00 PM
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Battery tray

Have started to make battery trays.
Will tie the packs down and also secure with velcro.
Steel pin in front edge will give vertical support, dowels with pins will
lock in rear in all directions.
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Old Dec 07, 2009, 01:04 PM
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Unusual solution again

Have put ring solder ends on all batterys.
Will make all power inteconnections with three pole screws.
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Old Dec 07, 2009, 01:12 PM
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Servo cradle

Made my own rudder servo cradle with help of some part from a brushless motor.
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Old Dec 07, 2009, 01:15 PM
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Landing gears

Do NOT like the landing gear legs included (for sale!)
My own construction are now baking in the owen.
Will weigh about 100 gr less and be flexible and somewhat higher (in case I want to test a 28" prop)
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Old Mar 11, 2010, 10:55 AM
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Finnished but not flown yet!

Sorry I left you guys, I continnued the story "back home"
You can watch if you want here:

http://mini-iac.se/forum/topic.asp?T...34&whichpage=7
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