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Old Jan 20, 2007, 07:21 AM
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Greg Browne's Avatar
Berkshire - UK
Joined Nov 2006
60 Posts
Quote:
Originally Posted by Andy W
??? It's not possible to wire brushless motors in series!


You need each motor connected to their own ESC, and the ESC's connected to the battery in parallel (positive to positive, negative to negative)..
..a

2 motors connected to 2 ESC's.

Power leads from ESC's wired in Parallel to + and - of Batteries.

THE BATTERIES ARE WIRED IN SERIES + TO - TO + TO -

And the ESC's are wired as i said to that then.

HELP
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Old Jan 20, 2007, 10:59 AM
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Ben_E's Avatar
Bergen, Norway
Joined Nov 2002
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Quote:
Originally Posted by Greg Browne
I have two 2s 1200 mAH in series with the 25amp ESC's.
Connecting batteries in series is not a problem, and he has two ESC's as well...

Ben_E
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Old Jan 20, 2007, 11:34 AM
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LK2TINKR's Avatar
Long Island, New York
Joined Apr 2006
374 Posts
Greg,

If I read your post correctly, you've got 2 2-cell, 1200 ma batteries connected in series which gives you a 4-cell, 14.4 volt pack. If this is correct, then it's also probably the source of your problem. The set up as sold by ACW is meant to be run with a 3-cell pack and draw 17 amps at full throttle (each motor). In your set up, each motor will want to pull around 23 amps for a total of 46 amps from the battery. The battery can not supply the current so the voltage drops rapidly. One of your ESC's kicks out before the other one which then allows the voltage to jump up and supply more current to the fan that's still running. You'll need to use 1 or 2 3-cell packs to solve the problem. If you have a 3-cell pack that can supply around 35 amps or so (say a Gen 2 TP 2100 pack) hook it up and try it.

LK2TINKR
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Old Jan 20, 2007, 01:38 PM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
43,312 Posts
Looks like Lk2TINKR nailed it - there is no 1200mAh LiPo battery capable of providing the current you need, and you should be running a single 3s pack (3 cells in series, but connected internally)..

Sounds like you have the ESC's wired correctly.
..a
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Old Jan 20, 2007, 02:18 PM
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DiabloKid's Avatar
Centreville, VA
Joined Jan 2003
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Gregs problem had me scared as I have been eyeing that setup for when I start mine
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Old Jan 20, 2007, 06:48 PM
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oldpilot's Avatar
Australia, NSW, Mona Vale
Joined May 2002
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GREG.

You could solve your problem by simply connecting your batteries in parallel---but then you would not get the plane to fly well, if at all, on 2s.

Any way you look at it you need 3S.

Cheers. Paddy.
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Old Jan 20, 2007, 10:02 PM
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DR1Driver's Avatar
Pulaski, TN
Joined Nov 2004
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Hmmm

Looks like someone had fun with the idea of the 380.
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Old Jan 21, 2007, 03:25 AM
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Greg Browne's Avatar
Berkshire - UK
Joined Nov 2006
60 Posts
LK2TINKR: Thank you very much thats what's happening word for word!

One motor running faster and then suddenly the other slows and eventually dies.

So what battery should i buy excatly? Can you pick it from this list? So i can order etc etc.

Thanks

http://www.aircraft-world.com/shopdi...o+%2D+HYPERION
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Old Jan 21, 2007, 05:48 AM
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Australia, NSW, Mona Vale
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GREG.

Suggest you go to http://www.aircraft-world.com/shopexd.asp?id=4528

and choose one of the three recommended batteries there.

Cheers. Patrick.
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Old Jan 21, 2007, 06:22 AM
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Greg Browne's Avatar
Berkshire - UK
Joined Nov 2006
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Hi patrick

I did...

i bought two of these? http://www.aircraft-world.com/shopexd.asp?id=3759

But somebody previous suggested something different?
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Old Jan 21, 2007, 07:45 AM
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LK2TINKR's Avatar
Long Island, New York
Joined Apr 2006
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Hey Greg,

Glad to have helped, I know how frustrating it can be... In general, this plane seems huge and can probably lift a lot of weight so I wouldn't be too concerned to go with the lightest solution. If cost is an issue, go with the highest capacity cells that you're willing to buy. In my opinion, if the battery is sized so that the 20C rating for it is the actual power level that's required, let's say 20C, 1200 mah battery to supply 24 amps needed, the flight times become a problem because the battery would only last 3 minutes of full power. The rule of thumb I'm using with 20C batteries is to size it at 12C for my full throttle needs. In your case this would translate into 2 3-cell, 1500 mah packs (or bigger) or 1 3-cell, 3000 mah pack (or bigger). Good luck with your project.

LK2TINKR
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Old Jan 21, 2007, 08:35 AM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
43,312 Posts
.. as you have two of the 1200's, you could try connecting those in parallel. Make sure they are both fully charged before you do!
..a
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Old Jan 23, 2007, 11:33 AM
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Greg Browne's Avatar
Berkshire - UK
Joined Nov 2006
60 Posts
Hi guys and gals (although i havent seen many gals around here) hee hee

I had enough and went to my local hobby store today.

I bought 3200mAH 3cell 11.1v lipo... Along with that , all new gold connectors and better duty wire!

Fingers crossed !!!! I should have all the soldering done tonight with a test for tomorrow!
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Old Jan 24, 2007, 06:26 AM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
43,312 Posts
OK, replacement battery came in, cycling this week, and targeting Saturday at sunrise for the maiden. Wish me luck!
..a
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Old Jan 25, 2007, 09:15 AM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
43,312 Posts
Final control throw setup, power tests and high-speed taxi tests last night. Hee-haw!

Steering works great now with gear servo reduced back to about 50% throw. Helped along with differential thrust, it gets around pretty good, but nowhere near as tight as before (but that pretty much ripped the gear around!)..

Turn off differential for takeoff and flight, reduced steering makes the model very stable but easy to correct as speed increases. Interestingly, even relatively hard turns at high speed don't cause the model to tip - my gear is doing it's job!

Power test showed 41A and 280W peak with a freshly-charged 2s 4000mAh pack. That gives me, say, about 5 minutes at full power, which, if that much is actually needed, I'll be keeping the flight short!

I have 4 ESC's with their own BEC is there, all 3A rated PHX25's. The middle two are paralleled to drive the tail surfaces and nose gear servo, the outer two only drive a single aileron servo. So, if I have to go up to 3s, I'm not worried about overheating.

Also, at 41A, that's only 10A/ESC - tons of headroom there. I just worry about the fans if I have to bump up the power. Also, if I have to go up to 3S, the weight is going to go up a good bit, and mess with my CG.

Speaking of CG, all that's left to do before the maiden on Saturday is fine-tune it - right now I'm a hair behind recommended, I'd rather move the battery forward than add weight - even if I it takes less than an ounce to balance it..

Anyone have pitch speed and thrust numbers for the GWS 55mm 5-blade fan running @ 70W? Acceleration and speed on ground look good at full power, but it would be nice to know what the numbers are..
..a
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