Go Back  RCU Forums > Electric Aircraft Universe > Electric RC Jets
 What C rating is best >

What C rating is best

Notices
Electric RC Jets Discuss rc electric ducted fan or radio control prop jets here.

What C rating is best

Old 12-06-2011, 08:31 PM
  #1  
Thread Starter
My Feedback: (8)
 
DaveJohansen's Avatar
 
Join Date: Aug 2003
Location: Taber, AB, CANADA
Posts: 237
Likes: 0
Received 0 Likes on 0 Posts
Default What C rating is best

I just purchased a Stumax 110-52 fan unit. Runs on a 12S 5000mah pack with a 110-120A esc. Trying to figure out what C rating I should be looking at, is higher ratings better? 50C vs 25C? Do higher C ratings maintain voltage better?

New to electrics,

Thanks

Dave
Old 12-07-2011, 12:10 AM
  #2  
My Feedback: (7)
 
djsqueeze's Avatar
 
Join Date: Dec 2007
Location: Katy, TX
Posts: 90
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best

Lithium Polymer (LiPo) Basics
It can sometimes be difficult to know which battery is best for your application.
For R/C aircraft there is a huge variety of batteries available and while many may suit your application your ultimate goal is to purchase a battery pack that will;
-be within your budget
-have a long cycle life
-have the correct size and weight
-give you the longest flight times
-be able to deliver the correct voltage/amp (Power)
We hope this simple guide helps you understand the different types of LiPoly (Lithium Polymer) batteries and which is right for your model.

You may have noticed by now that batteries have different ratings, sizes, plugs, wire, charge rates and chemical makeup. Lets decipher;

Capacity (mAh).
This is usually the biggest number shown on the pack and is measured in mAh (Milliamp/hour) or Ah (Amp/hour). The capacity is the first indicator of the batteries size. To keep things simple, think of capacity (mAh) as the amount of fuel in your cars gas tank. A higher capacity tank will run your car for longer. A 4,000mAh battery will run for twice as long as a 2,000mAh battery.
A 2,000mah battery will (in theory) run for 1hr if drained at a constant 2,000 Milliamps.

Discharge (C)
Discharge is the amount of power the battery can 'push' out and the number shown '20C' is an multiplication of the capacity. For example; A 20C battery can discharge at 20 x 2,000mAh which is 40,000mAh or 40Amps.
This is an important number if you know your motor requires a certain power level.
In addition to this, batteries have a 'Burst' rate, which is the amount of power the battery can discharge for a short period, usually 10-20 seconds. A typical battery label may show 20-30C, this would mean a 1,000mAh battery can discharge 20,000mAh constantly or give a sudden and short 10-20 second 30,000mAh (30A) burst of power.
Tip: A higher 'C' rated battery will last longer if run at a lower 'C' rate. Example: a 30C battery run at 20C maximum will have a longer cycle life than a 20C run at 20C each flight.

Voltage (S)
All lithium Polymer cells in any industry have a nominal voltage of 3.7v per cell. When fully charged a LiPoly cell should be 4.2v and when discharged it should never be below 3v.
You will notice that LiPoly RC packs are made up of layers of multiple cells. If the battery's rating is 3S this means it is 3 x 3.7v which is 11.1v. It has 3 layers of 3.7v each. In other words, its a '3 cell pack'.

Weight/Size
For a battery to be right for your model it must fit within the models battery compartment and also balance the plane correctly.
It's temping to choose the biggest and most powerful battery your model can handle, but this will sacrafice flight performance and if your packs voltage is too high; destroy the ESC or Motor.
Check with your ESC and Motor specification to ensure you have the right voltage pack then check the models CG (Center of Gravity) to decide on the right battery weight.


LiPoly Charging
Always use a lithium Polymer battery charger and never charge the battery above 4.2v per cell. (example: 2S, never above 8.4v)
Never leave a charging battery unattended.
Never allow the battery's voltage to fall below 3v per cell. (example: 3S, never below 9v)
Old 12-07-2011, 05:58 AM
  #3  
My Feedback: (11)
 
BarracudaHockey's Avatar
 
Join Date: Jul 2003
Location: Jacksonville, FL
Posts: 27,076
Received 361 Likes on 290 Posts
Default RE: What C rating is best

One small correction.

Batteries don't push. The higher C rating allows more amps to be drawn out. Specifically, more amps can be drawn without damage (puffing) to the battery.

Its a small but important distinction.

Since everything comes with a price (in this case litterally) higher C rated batteries both cost more and weigh more.
Old 12-07-2011, 06:52 AM
  #4  
Thread Starter
My Feedback: (8)
 
DaveJohansen's Avatar
 
Join Date: Aug 2003
Location: Taber, AB, CANADA
Posts: 237
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best

Thanks for the input guys. So the motor on this fan will draw 80-90 amps, calculating that out at 20C/30C burst 5000mah pack is rated to provide normal 100A with bursts of 150A.

20C sounds sufficient so what is the benefit of of going to a pack that is say rated 30C/40C burst or higher?

Dave

Old 12-07-2011, 09:03 AM
  #5  
My Feedback: (9)
 
juanjulian's Avatar
 
Join Date: Nov 2003
Location: guatemala, GUATEMALA
Posts: 544
Likes: 0
Received 1 Like on 1 Post
Default RE: What C rating is best

Go with 30c and above rating for your cofiguration.

You will benefit for having more instant power ass the motor can draw the current more easily from the batteries.

The 20C work but they won´t last as long.

Cheers,

Juan



Old 12-07-2011, 09:47 AM
  #6  
Senior Member
My Feedback: (5)
 
Join Date: Mar 2002
Location: Huntsville, AL
Posts: 295
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best


ORIGINAL: DaveJohansen

20C sounds sufficient so what is the benefit of of going to a pack that is say rated 30C/40C burst or higher?

Dave

Dave;

Ditto on Juan's recommendation!

Regards,

Gary Taber
Old 12-11-2011, 06:28 PM
  #7  
 
Extreme_RC's Avatar
 
Join Date: Oct 2008
Location: , AUSTRALIA
Posts: 424
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best

Regardless of C rating, you should really not run your setup at more than 20c constant. 35c packs, 45c packs, doesnt matter, I try to keep large setups at 20c max. You are better to go up in pack size, 6000mah would be ideal in a 30-35c rating for the SM110 fan as opposed to a 45c 5000mah pack.

And protect your packs with a high cutoff voltage setting in the ESC, 3.1-3.2v per cell minimum. Most damage occurs when the pack is discharged past 90% of its capacity, combine this with a high discharge rate and damage occurs very easily if you deplete them.

Old 12-12-2011, 02:52 PM
  #8  
Senior Member
 
Join Date: Jul 2002
Location: coral springs, FL
Posts: 434
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best


ORIGINAL: DaveJohansen

I just purchased a Stumax 110-52 fan unit. Runs on a 12S 5000mah pack with a 110-120A esc. Trying to figure out what C rating I should be looking at, is higher ratings better? 50C vs 25C? Do higher C ratings maintain voltage better?

New to electrics,

Thanks

Dave

get the highest C rating you can afford
Old 12-12-2011, 03:14 PM
  #9  
My Feedback: (15)
 
Join Date: Apr 2004
Location: Aurora, CO
Posts: 1,297
Likes: 0
Received 2 Likes on 2 Posts
Default RE: What C rating is best

But why pay for a 50c pack if you are only pulling 30c? The prop/motor dictate the targeted amps pulled.

Kurt
Old 12-13-2011, 02:23 PM
  #10  
Senior Member
 
Join Date: Jul 2002
Location: coral springs, FL
Posts: 434
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best


ORIGINAL: rcand


ORIGINAL: DaveJohansen

I just purchased a Stumax 110-52 fan unit. Runs on a 12S 5000mah pack with a 110-120A esc. Trying to figure out what C rating I should be looking at, is higher ratings better? 50C vs 25C? Do higher C ratings maintain voltage better?

New to electrics,

Thanks

Dave

get the highest C rating you can afford
from what others tell me is with the higher C you also get the higher voltage longer, therefore, better performance. Example, I have a Habu with a 45C 3200ma battery. A friend of mine has the stock battery, I thinkd 30C, but upgraded the motor for more power. One time we were flyer together and he can't figure why his more powerful motor can't catch mine. Only answer is the battery. Another, a friend of mine has aBVM eclectra that was running on 12S with 45C batteries. He converted to 10S with 65C batteries. Even though he now is running on 2 less cells, he did not lose speed or performance.
Old 12-15-2011, 08:48 AM
  #11  
My Feedback: (9)
 
juanjulian's Avatar
 
Join Date: Nov 2003
Location: guatemala, GUATEMALA
Posts: 544
Likes: 0
Received 1 Like on 1 Post
Default RE: What C rating is best

The main diference from lower to high C rate is the internal resistance of the packs. Higher C rates have lower resitance.

If you have a nice charger there is a possiblity you have a option to measure internal resistance of the battery.

In my case I have some4 year old electric flight 3200 mah 3S 20C , that paid like $120 for each pack on those days, and measured 120 ohm.

Recently boughta china 3s 3700mah 35C and measured 10 ohm.

It seems like this are only numbers, but with the 20 c battery the jets needs almost all the airstrip to rotate and lift, and with the 35C the jet needs 1/3 of the air strip to get airborne.

Less resitance gives more instant current (juice) that translates into more power with the same setup.

Think 20C is ok normal power aplications but for high power aplications as in edf jets they are marginal

My jet flies marginall with 20 c batteries and with the new high C rates batteries it came to life.

Today Lipos pirce is very afordable and for $120 you can get 4 3s 4000mah 40c rating at hobby king.

Think is cheaper to have a good high C rate Battery than to upgrade to a hig power motor setup.

Cheers,

Juan
Old 12-16-2011, 09:26 PM
  #12  
My Feedback: (20)
 
Join Date: Jan 2008
Location: Frederick, CO
Posts: 5,973
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best


ORIGINAL: DaveJohansen

Thanks for the input guys. So the motor on this fan will draw 80-90 amps, calculating that out at 20C/30C burst 5000mah pack is rated to provide normal 100A with bursts of 150A.

20C sounds sufficient so what is the benefit of of going to a pack that is say rated 30C/40C burst or higher?

Dave

If your fan pulls 80-90amps I would not go with anything less than 2x that
so something that can put down 180amps+ cont. from the packs..
you also will have less voltage drop and have more speed and thrust from the EDF
Old 12-23-2011, 09:11 AM
  #13  
My Feedback: (13)
 
SCALECRAFT's Avatar
 
Join Date: Jan 2002
Location: MONTEBELLO, CA
Posts: 2,649
Likes: 0
Received 1 Like on 1 Post
Default RE: What C rating is best

Note that "c" ratings, from what I have seen are a bit generous when putting a number to it.

Certain brands label 20,30,40c, but fall short of some others brands I have that are "c" rated less, but supply more current.

So get the extra rating, chances are they will fall short in actual use.

Remember, "Results may vary".............

steve
Old 12-23-2011, 09:34 AM
  #14  
My Feedback: (11)
 
BarracudaHockey's Avatar
 
Join Date: Jul 2003
Location: Jacksonville, FL
Posts: 27,076
Received 361 Likes on 290 Posts
Default RE: What C rating is best

+1

Generous to the point of fanciful is some cases.
Old 12-26-2011, 12:06 PM
  #15  
Senior Member
 
Bill G's Avatar
 
Join Date: Apr 2004
Location: Grove City, PA
Posts: 230
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best

What C rating is best?

Couldn't pass this one up: One that doesn't lie.

There's nothing more full of baloney that ESC and battery ratings. Word of mouth from, you guessed it, the EDF folks who are pushing stuff the hardest, is probably the best info. I get a kick out of those folks who submit a battery review on a 35C lipo saying, "Excellent lipo, works great in my Slow Stick". Once you find out what the real C rating is, then you can go from there.
The most sensible advice I've heard, is that if you want your lipos to hold up reasonably well, then try to size them for the draw to be at 20C and under.

ORIGINAL: juanjulian
In my case I have some 4 year old electric flight 3200 mah 3S 20C , that paid like $120 for each pack on those days, and measured 120 ohm.
Isn't that a real scorcher though, realizing what we paid for some of this stuff, a few years back! [X(]
I was searching for a specific receipt a few days ago, and got really depressed when I saw what I was paying for stuff back in 04-05, and then thinking about how little I would have to pay to buy the same thing today.
Old 12-26-2011, 03:53 PM
  #16  
 
Extreme_RC's Avatar
 
Join Date: Oct 2008
Location: , AUSTRALIA
Posts: 424
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best

Exactly, us EDF people know what batteries are good and what are not, we expect high constant disharge performance, flying a nanotech pack in a parkflyer gives you no idea as to the packs performance, stick it in a jet running at 20-25c constant and fly it hard until its 90% discharged, see how it fares after a dozen flights.

I have seen 45c nanotech packs blow up like balloons on the first flight running at 30c, and I always tell my customers to size their batteries for a maximum continuous amp draw of around 20c, with 25c being the max on our 45c packs. Premium cells cost money, I cannot purchase the best cells for the price HK sells their packs for, the reason is not profit margins as the chinese work on small set margins with this stuff, its material quality and production QC that costs more with the premium cells.

You get what you pay for, cheap packs are fine in setups that require low amp draws, but move up to hi performance and the premium packs shine not only in power delivery but in cycle life too.
Old 01-03-2012, 03:16 PM
  #17  
My Feedback: (23)
 
Join Date: Dec 2004
Location: mt dora, FL
Posts: 518
Likes: 0
Received 0 Likes on 0 Posts
Default RE: What C rating is best

the genace packs from hobbypartz have performed better then tp and xps 65c packs. there are many edf pilots to attest to this. both 25c and 30 pack from genace outperformed the 65c packs. there is a HUGE gap in the C rating method used by some domestic DISTRIBUTORS.

Ive also had great success with Sky Lipo's. They've preformed excellent under high amp conditions, repeatedly, same as the GA's.

one big factor ive learned over the years is that "" a premium priced battery" ISNT a "premium quality battery"

dont get fooled by the domestic dealers who inflate the C ratings and MOST of them are doing it, including the top names. most those "premium" packs have poorly matched cells, high IR and are seiously over priced from exchanging hands.

the cold hard truth stings for some...

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On


Thread Tools
Search this Thread

Contact Us - Manage Preferences Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.