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Old Jun 20, 2001, 12:21 AM
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hoser's Avatar
United States, FL, Miami
Joined May 2001
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Fans in series or parallel

are there any advantages to twin fan set ups in series.

and what would be the basic design criteria.

for example, for a twin midi fan set up they recommend 20 cells with an ultra 930-10, (which I assume has a lower RPM / volt than the 930-6)

however if you connect one single 930-10 to 20 cells you get "X'"rpm's and "X" amps. when in series do you get 2 fans with "X" rpm's and "2X" amps ???
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Old Jun 20, 2001, 03:23 AM
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Doc Watson's Avatar
UK
Joined Mar 2000
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There is a big difference.

Parallel circuits will see the same voltage from 20 cells so 20V (approx) will be seen. However the amps that will be pulled from the cells will be doubled so if one motor pulls 30A then the battery pack will be drawing 60A. This reduces duration by 2.

In series each motor will see half the voltage (10V) but will pull the same amount of amps. So if one motor pulls 30A then the battery pack will be drawing 30A.


Hope this helps

Doc
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Old Jun 20, 2001, 06:42 AM
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St. Louis, Missouri, USA
Joined Nov 2000
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Greetings!

Adding to what Doc said, you have to take into account whether your cells and esc can take that kind of load - 60 amps is abusive to cells - plus what number of cells will your model need to carry. Which all leads to sizing of the model, weight, speed, etc., etc., etc.!

Don't let that stop you, we need to see more twins flying.

Fly Fast! Mark
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Old Jun 20, 2001, 11:45 AM
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St. Mary, Maryland, United States
Joined Dec 1996
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The 930/10 is recommended for parallel setups because it isn't drawing much more than 15 amps on 20 cells. So 2 of them in parallel on 20 cells will be drawing something under 40 amps which is just what you want.

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Old Jun 20, 2001, 04:35 PM
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United States, FL, Miami
Joined May 2001
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THERFORE.... in twin set ups is series better assuming your kit can take the weight of the extra cells.


example if I run my A-10 on 12 cells parallel, then to get the same performance I would need to run that set up on 24 cells series to maintain same performance or use hotter motors and less cells.

"assumption" - a series set up should give the same performance, only the volts get divided by the number of motors in the series.

BUT, are there advantages (to a series set up) as far as flight time and efficiency, since now these motors will run at a lower load or do you suffer a bit on Rpm's ???

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Old Jun 20, 2001, 05:16 PM
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Reno, Nevada
Joined Jan 2001
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OK, on my learjet I originally ran (1) 8 cell pack to each ESC and Motor, then I changed over to a series set up with 1 16 cell pack to 1 ESC to motors in series. I noticed a little bit better efficiency on the series set up in terms of duration, but little (if any) boost in performance, and lost the weight of one ESC.

Then I changed over to motors with lower KV (rpm per volt). Now I am running a parallel set up using 16 cells. My duration is now 1/2 of the above set ups. But the performance is better because the fans are turning faster.

My Dornier Jet can only handle 10 cells max. So I am using high kv motors in parallel on 1 10 cell pack.

It is a balancing act that you have to play between the weight, capacity, and current draw limits of the batterys versus the performance of your motors (Kv, current draw)/fan systems, all compared to what your plane can hold, carry and still fly with a desired performance level.

[This message has been edited by Plane Crazy (edited 06-20-2001).]
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