• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.
Pumpkin drop event

got a question about c ratting

Arcfyre

Well-known member
#2
My question is if i have a 30A ESC would a 25C ratted battery be ok to use with it or should i go with at least a 30C ratted battery?
They don't compare like that. You need to do the math to turn battery C rating into amps first.

Simple formula is C rating x Amp hours of battery capacity = amp output

So a 25C battery with a 1000mah capacity would be:

25 x 1 = 25 amps.

Your motor and specifically the prop determine the amp draw on your system. The same motor will pull different amps with different props on it. A large diameter, coarse prop will pull more amps than a small diameter flat pitch prop, all other things being equal.
 

ElectriSean

Eternal Student
Mentor
#3
C rating is based on the capacity of the battery. The max discharge is the C rating x the capacity in Amps, so a 25C 1000mAh battery can provide 25A - 25 x 1A. A 25C 1300mAh battery can provide 32.5A. Beware also that C ratings are almost always over rated.
 

Merv

Well-known member
#4
It will depend on the size of battery. To calculate how many amps a battery can provide, take the mAh/1000 x C.
Example a 2,200 mAh, 25C battery can safely supply 55 amps (2,200/1000 x 25)
 
#5
ok thanks was looking at a battery in the 10000 mah but the c ratting is 25, so the amps it could supply constantly would be 250, so i would be ok to use it to increase my flight times
 

Arcfyre

Well-known member
#6
Yes, assuming whatever you're flying can get a 10000 mAh battery off the ground. That going to be a brick. Mind if I ask what model you're putting that in?
 
#7
one thing would be the sea duck, the other will be a project plane (b-17)
yeah i know it is a brick but i figure if i can fly longer with it while teaching my nephews its a good trade off
 
Last edited:
#8
A sea duck might possibly be able to fly that battery but probably not. ft recommends 2200mah. THe highest I would go would be 3500 mah.Just get like 3 and you will get more flight time for a lot less cost. Just land and switch. It's not that hard.
 

Merv

Well-known member
#9
i know it is a brick but i figure if i can fly longer with it while teaching my nephews its a good trade off
With a battery that large, it’s doubtful you’ll get the Sea Duck off the ground. If you did, it would not fly very well, too much weight. The wing loading would be too high. You would be far better off with 4 smaller batteries than 1 larger one.
 

Wildthing

Well-known member
#10
ok thanks was looking at a battery in the 10000 mah but the c ratting is 25, so the amps it could supply constantly would be 250, so i would be ok to use it to increase my flight times
Just curious about the size , is it right or is it a typo? 10,000 mah as you stated or did you mean 1,000mah?
 

FDS

Well-known member
#13
I like to think of the battery as the aircrafts fuel tank. It is designed to carry a certain fuel load (recommended batteries!) but as the user/pilot you have some leeway. You can put less fuel in and have the plane lighter, for more nimble, floaty but shorter flights, or you can fill it to the brim and add drop tanks with a larger battery and accept the extra weight will impact performance or CG etc.
What you can’t do is tie two full fuel trucks to the wings and park one in the cargo area, then hope your bird will fly.
A 10ah battery is way too large for the type of planes FT build, as noted above you would be better off buying 5 smaller packs and using them one after another. You can increase flight times by getting greater efficiency out the motors with sound prop choice and sensible throttle control. Telemetry can help you manage the battery voltage so you get all the flight time out of packs, as can good battery management with a timer.
 

FDS

Well-known member
#16
A 10Ah battery will work, but the plane will fly like a brick. Possibly straight down.
A 2200 30c will easily meet the requirements of a foamboard twin.
C rating is a function of capacity. To find the true peak output take the C rating x battery capacity in AmpHrs not Milli amp hours.. So a 2200mah 30c can actually do 30x2.2= 66A.
ESC’s don’t draw current, the motor does, the ESC is just the electronic controller for the motor, if the motor draws more than the ESC is rated for then it gets hot or smokes. Motors don’t draw their full max current all the time either, for example when you are cruising round at moderate throttle, the motor won’t need as much “fuel” and so doesn’t draw as much current. Current draw is related to load on the motor, faster turning with a bigger prop = more load, for example.
 
Last edited: