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Old Today, 11:33 AM
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FNFAL's Avatar
Dayton, OH
Joined Oct 2006
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Question
Affect of C rating on EDF peformance?

I would like to know if anyone has some experience to what affect the Lipo C rating has on the EDF thrust output?

Let's say a 25, 55, and 70C lipo of all the same capacity, and the rated EDF current (~20C) is all under the continuous ratings of said lipos. What % are we talking? Very small?
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Old Today, 11:44 AM
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4stripes's Avatar
Canada, ON, Burlington
Joined Jan 2009
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HUGE impact on performance. High amp draw will draw lower C rated battery voltage down fast and it will give much fewer usable cycles.
Go with the best C rating you can afford. For me 45c with a top brand name battery like GensAce gives decent performance for the money. 45c cheap Chinese batteries, will not do the same.
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Old Today, 11:56 AM
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Dayton, OH
Joined Oct 2006
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Thanks. It just feels like all that extra "C" is a waste of money, not to mention any weight savings I can get...but if performance reduction is significant than that IS a concern.
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Old Today, 12:01 PM
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St. Mary, Maryland, United States
Joined Dec 1996
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I'd say it depends on how high and how long the actual load is as well. In other words, for something like a 6S Foamy where you tend to be operating at high throttle for more of the flight if your load is approaching 20C then yes, you want at least a 40C pack and you will notice the performance difference a lot. For a 10 or 12S big plane where the load is more like 15C because you are carrying bigger packs sometimes 30C is fine. 20C & 25C packs universally seem to be garbage in my experience. I've had good luck with 30, 40 and higher C packs.
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Old Today, 12:09 PM
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Dayton, OH
Joined Oct 2006
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Thanks. If it helps any, I'm looking at a 6 or 7S app with an 80mm fan running a 5000mah latest TP Lipo. But I may already have the answer, as I now notice TP has a new pricing structure and the 55C is actually cheaper than the 25C by a significant amount.
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Old Today, 12:33 PM
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55c cheaper than 25c?
Can you post a link to your vendor?
Thanks!
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Old Today, 12:45 PM
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Dayton, OH
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Sure:

http://www.thunderpowerrc.com/Products/AIR-BATTERIES
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Old Today, 01:09 PM
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Thanks!
Looks like TP are getting more competitive in price.
That's good!
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Old Today, 01:14 PM
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Dayton, OH
Joined Oct 2006
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Indeed. I have no info, but it has all the feelings of the 55C being from a different supplier than the other two. But either way, it's got TP's blessing...so for what it's worth...which could be good or bad depending on your prior TP experience.
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Old Today, 01:18 PM
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Quote:
Originally Posted by FNFAL View Post
Thanks. If it helps any, I'm looking at a 6 or 7S app with an 80mm fan running a 5000mah latest TP Lipo. But I may already have the answer, as I now notice TP has a new pricing structure and the 55C is actually cheaper than the 25C by a significant amount.
I'm no way a master with electrics but have been recently getting involved in them due to my growing interest in EDF aircraft. Over the past several months I've been putting a Habu 32 together and of course doing the very wise thing of asking lots of questions from very experienced EDF pilots, vendors, etc. in regards to power configurations and batteries.

From what they've all indicated, yes, if you increase the c rating, you will increase the output numbers. It is important to know that there is a formula that they use to determine this. The formula includes the kv rating of the motor you're using and how many cells, mah and discharge rating of the batteries you're using.

Most everyone I have discussed this with pretty much say the same thing about the mah size. The mah basically is the "size of the tank" or how long it will run. The c rating is how much the battery is capable of dumping. Of course all the numbers do play a role in how much power output is. I don't know what that formula is however.

The quality of the battery is another factor in how long the battery will perform and can be used. Cheaper batteries most times have a shorter service life than compared to the more top end expensive batteries. I've used both e-flite and Thunder Power. Thunder Power are the batteries I use in my Habu 32. E-flites are what I use in stuff like my foamy Habu and Stryker.

In regards to brand new battery prices, higher c rated batteries will always cost more than lower c rated batteries, unless you're dealing with cheap stuff you're buying on line from outside the U.S. (primarily from China). Because you really don't know what they are doing with batteries over there. They may have a cheaper 55c rated battery compared to the 25c rated battery. but cheaper perhaps because it's made of materials and components that may have a half the service life of the 25c rated batteries they are producing and selling.
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Old Today, 01:35 PM
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Dayton, OH
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All good points and ways to consider...thanks...
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