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Old Jan 17, 2003, 03:09 PM
I ain't got it!!!
USA, SC, Spartanburg
Joined Apr 2001
867 Posts
Help with Batteries/Prop for Mega 15/16/4

I have a Combat Wings XE 400 which I fly with a Mega 15/16/4 and usually with 8x600AEs.

1. What's the best prop for speed with this setup?
2. Would I hurt anything if I used 10x500 ARs ?
3. Would an 8x1400 KR pack hurt anything?


Thanks,
Adam
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Old Jan 17, 2003, 04:15 PM
Plane dodger
KillerAir's Avatar
Stratford Sikorsky, Connecticut, United States
Joined Dec 2001
6,715 Posts
Adam, to take full advantage of the power potential of the Mega 4T you're going to have to get better cells. You may be able to pull about 12A out of those AE cells at say 7.5v at WOT. This will get you about 90w in and about 75w out. The AR's (unless they are the older red ones) aren't any better power wise. If you go to a HE1100 you can get about 15A out max but the voltage drop is less than the ae's. 15Ax7.8v=117x.85= 99w out. Go up to a CP 1300 or better yet a HR1700AUP NiMH and get up to 30A out. So your max power is now restricted by your motor not your source. Propped for 25A at 8.2v you'll see 205w in and 175w out. Significant difference from the ae's. The power will more than make up the difference in weight increase, not to mention about 10minutes of flying as compared to 4minutes on the 600's. I believe most guys are running a 5x4.7e with great success.
As for the KR cells, I think you'll fry them, I think the KR cells are duration cells not high current cells.
Hope this helps

Killer
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Old Jan 18, 2003, 10:06 AM
Registered User
Uvalde, TX
Joined Sep 2002
105 Posts
I'm building an XE2-400 right now and will be putting a Mega 16/15/4 on it. I did a lot of research before ordering my equipment and I chose CP1300 SCR cells instead of the HR1700 AUPs (against the advice of some). From what I gathered, the HR1700 AUPs are much fussier than the CP1300s and will take significantly longer to charge. According to this guy, the CP1300s gave his brushless Zagi the best performance and they take less than 20 minutes to field charge: http://home.flash.net/~jecramer/zagi.htm

Others here have told me the HR1700 AUPs require anywhere from 30 to 45 minutes to field charge, depending on whether you want to "push" them. Others said you should never push these cells when charging them. Either way, the charging times appear to be significantly longer than the CPs which are "rapid charge" cells. I don't understand the advantage the HRs offer - so you maybe gain a minute or so in flight duration but then they take twice as long to charge.

For me, maximizing stick time in a flying session is more important than maximizing duration for a given battery pack. I hate being grounded waiting for packs to recharge.

P-calc showed the 6x4 prop to be the most efficient for this entire set up, with an efficiency rating very close to the maximum possible efficiency. To be safe, I ordered an assortment of different props in this diameter/pitch range.

Hope this helps.

Houdini
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Old Jan 19, 2003, 04:31 PM
My cat up close
bipeflyer's Avatar
England
Joined Feb 2001
4,021 Posts
I wonder if someone could help me here?
I have a new model almost ready to fly now,a scale 25" span SU 27.
I'm a little confused by the data.If I use a 10 cell CP1300 pack,I can draw 25Amps right? If so,that would give me 5 mins WOT.
So,what confuses me,is the 10 minute claim.

Could you please clarify,the 10 minutes is with conservative throttle usage?

Hope you can assist!

BTW Any prop make/size reccomendations for this model? I want to handlaunch it.
Here is a pic:
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Old Jan 20, 2003, 03:44 AM
I ain't got it!!!
USA, SC, Spartanburg
Joined Apr 2001
867 Posts
Thanks Guys!

If I go with the 1300SCRs, should I get 7 or 8 cells? Same question with the other packs...?? Sorry for the confusion


I might have to try a few packs of each now! Thanks for the help!





Adam
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Last edited by Flying Low; Jan 20, 2003 at 03:47 AM.
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