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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Tom Strom on May 21, 2013, 12:07:11 AM

Title: C-rating on Batteries
Post by: Tom Strom on May 21, 2013, 12:07:11 AM

Hello.  I have a question on my Thunder Power Batteries.  I have the 5 cell, 5s, 2700mah, 25C batteries.  Are these too small of a C rating for my E-flite 32.  I am running an E-flite 32, Ice Lite 75 speed control, and Hubin FM-9 timer. 

I noticed a lot of people are running the 5 cell batteries with their E-flite 32.  However, the instructions say 2 to 4 cell only.  How do we get away with running the 5 cell?

Thanks in advance for the replies.

Tom

Title: Re: C-rating on Batteries
Post by: Jeff Traxler on May 21, 2013, 12:15:19 AM

Hi Tom,
    The C rate is the rate of maximum safe constant discharge.25C is fine for our needs.As far as the second question I can't help with that.Trax

Title: Re: C-rating on Batteries
Post by: Tim Wescott on May 21, 2013, 12:42:52 AM

We're not flying RC.  The eFlight 32 is probably rated for four cells to keep it from spinning too fast at max throttle and damaging the bearings.  So -- don't spin it up to full throttle on five cells.

Title: Re: C-rating on Batteries
Post by: Tom Strom on May 21, 2013, 12:45:10 AM

Thanks Jeff, and you too Tim!!  See you in a few days Tim.

Tom

Title: Re: C-rating on Batteries
Post by: Robert-Jan on May 21, 2013, 05:36:48 AM

Here it says 5S
http://www.e-fliterc.com/Products/Default.aspx?ProdID=EFLM4032A
The KV is to low to run on 4S if you use a 12x6 prop.

Greetings Robert-Jan

Title: Re: C-rating on Batteries
Post by: Allan Perret on May 21, 2013, 05:58:30 AM

Was comparing the specs of Power25 and Power32 on E-Flites site.  It says shaft size on 25 is 6mm and on 32 is 5mm.  Is that right ?

Title: Re: C-rating on Batteries
Post by: Dean Pappas on May 21, 2013, 07:06:15 AM

Hi Tom,
Running on the governor means that we are likely running on somewhere between 75% and 85% of the battery voltage to begin with.
The battery, Kv and prop pitch should never require "full throttle" from the ESC, because we want voltage headroom and "punch" for the Clover.
We often run a motor with one more cell than the motor's datasheet describes.
A Stunt pattern averages a roughly 7C discharge rate with peaks at 10C or so.
The marketting hype was such that a few years ago, some batteries were not up to the load of a Stunt run, but these days anything honestly marked as 17C or 25C is fine.

Regards,
  Dean P.

Title: Re: C-rating on Batteries
Post by: Tom Strom on May 21, 2013, 12:59:26 PM

Ok, thanks Dean.  That's what I was looking for.

Tom