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Author Topic: what does a higher c rating do?  (Read 1147 times)

Offline Matt Curtis

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what does a higher c rating do?
« on: January 10, 2022, 09:37:11 PM »
So if I run a 2200 4s 30c battery or the same battery with a 50c rating what does the higher c rating do?

Offline Frank Donnelly

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Re: what does a higher c rating do?
« Reply #1 on: January 11, 2022, 07:28:12 AM »
Think of the C rating as a multiplier that will tell you how much current the battery can safely deliver. The 2200 mah battery can provide 2.2 amps for 1 hour. With a C30 rating (2.2 X 30) = 66amps. The C55 rating would be 2.2 X 55 = 121 amp. The battery will not be able to deliver those high currents for and hour. The time goes down. Divide the C rating into 60 minutes to see how long it can deliver that amount of current.
So a 2200 C30 battery can deliver 66 amps for 2 minutes (60 /30 = 2).
A 2200 C55 battery can deliver 121 amps for about 1.8 minutes (60/30 = 1.8).

In control line we are not consuming that much current so you can typically get by with a 20c rating.

Offline Crist Rigotti

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Re: what does a higher c rating do?
« Reply #2 on: January 11, 2022, 07:31:48 AM »
Usually adds weight to the battery.
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Offline Howard Rush

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Re: what does a higher c rating do?
« Reply #3 on: January 11, 2022, 12:54:49 PM »
And cost.  It might be more entertaining when shorted.

25C seems to suffice for stunt.  We went through a 45C fad on the advice of a guy who didn’t believe in regulators.
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Offline Matt Curtis

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Re: what does a higher c rating do?
« Reply #4 on: January 11, 2022, 02:29:12 PM »
Thank you for the replies. This set up I am using is not for stunt. I testing the arrowwind ef-1 motor which is a high rpm pylon racing motor . prop is 8x8 thin electric battery is 2200 4s 30 c speed control 60 amp and I am running it  with a transmitter for throttle on a gold ber cosmic wind. It draws 48 amps with the trhottle at 80% rpm 13,800 i ran it for less than a minute maybe a minute and battery went down to 36% about 3.8 volts so I did not hurt the battery or the esc or the motor. I am only going to fly level for not very many laps I assume I would need to go to a 3200 mah battery but it is way heavier. i want the plane to go fast for a few laps and then land. I think the 3200 battery is 4 0zs heavier. I dont know if that is a good idea for the weight. I could recheck the stats with throttle at halfway to see what it does? I was hoping to get maybe 10 or 15 laps?

Offline Mark wood

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Re: what does a higher c rating do?
« Reply #5 on: January 11, 2022, 04:53:35 PM »
Thank you for the replies. This set up I am using is not for stunt. I testing the arrowwind ef-1 motor which is a high rpm pylon racing motor . prop is 8x8 thin electric battery is 2200 4s 30 c speed control 60 amp and I am running it  with a transmitter for throttle on a gold ber cosmic wind. It draws 48 amps with the trhottle at 80% rpm 13,800 i ran it for less than a minute maybe a minute and battery went down to 36% about 3.8 volts so I did not hurt the battery or the esc or the motor. I am only going to fly level for not very many laps I assume I would need to go to a 3200 mah battery but it is way heavier. i want the plane to go fast for a few laps and then land. I think the 3200 battery is 4 0zs heavier. I dont know if that is a good idea for the weight. I could recheck the stats with throttle at halfway to see what it does? I was hoping to get maybe 10 or 15 laps?

Here's something to understand. C rating is achieved by increasing the size of the internal conductors and the physical chemistry. A battery having a total amount of electrolyte, anode and cathode are capable of a specific amount of energy delivery. Watt x seconds or Watt hours. For a given weight you can parse that out in many ways depending on the internal conductors. Often times you'll see the same cell in two different batteries with two different  capacity and C ratings. When you take them and do the energy calculation you'll see they have the same Watt second capacity. What this means is that you will more than likely have to increase the battery size. No way around it. What you need to determine is how much battery you need in terms of Watt Hours. To do this you need to determine the power required on your next test. The current is only half the equation. It only tells you if the wires are gonna get hot including the ones inside the battery.

So you are trying to achieve a run of a given amount energy expenditure. You can calculate your Watt usage and time of flight to determine the energy capacity you need in Watt Seconds. Then from that you can determine how much storage you need and the C rating required. The specific energy of LiPo batteries very from 100 Wh/kg to 265 Wh/kg. Not knowing how long a lap is it's hard to say how big the battery must be.


So static power for that prop running 14 k is about 0.9 Hp which is 671 Watts. In flight at 100 MPH that power is going to drop down to 0.54 Hp and 402 Watts. Lets say the laps will take 5 minutes
 and the energy it takes to get up to speed is equivalent to one minute operation  6 minutes total or 0.1 hours. This means you need a minimum of 402 W x 0.1 hr = 40.2 Watt hours. Your battery and motor are matched for the 4s battery? It's important as the efficiency of the system will bite your effort if they aren't. Given that W= I x V and then current rating for you battery will be determined Icap = Whr / V. Since the previous calculation is solely what is required for the flight a 20% - 30% margin should to be added resulting in 1.2 x 40.2 = 48.2 W*hr.  Then the capacity Icap = 48.2 Whr / 14.8 V = 3.2 AH. Looks to me like you're gonna need that bigger battery.

Here's a useful data link to the 8 x 8 propeller in order to do some analysis yourself.

https://www.apcprop.com/files/PER3_8x8E.dat

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Online Dave Rigotti

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Re: what does a higher c rating do?
« Reply #6 on: January 11, 2022, 06:16:53 PM »
I'm curious as to your application/plane.  Is this for an electric speed event?

Thank you for the replies. This set up I am using is not for stunt. I testing the arrowwind ef-1 motor which is a high rpm pylon racing motor . prop is 8x8 thin electric battery is 2200 4s 30 c speed control 60 amp and I am running it  with a transmitter for throttle on a gold ber cosmic wind. It draws 48 amps with the trhottle at 80% rpm 13,800 i ran it for less than a minute maybe a minute and battery went down to 36% about 3.8 volts so I did not hurt the battery or the esc or the motor. I am only going to fly level for not very many laps I assume I would need to go to a 3200 mah battery but it is way heavier. i want the plane to go fast for a few laps and then land. I think the 3200 battery is 4 0zs heavier. I dont know if that is a good idea for the weight. I could recheck the stats with throttle at halfway to see what it does? I was hoping to get maybe 10 or 15 laps?
Dave Rigotti
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Offline Matt Curtis

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Re: what does a higher c rating do?
« Reply #7 on: January 11, 2022, 07:19:02 PM »
This plane is too heavy so I want it to go fast just for the fun of it. not for speed event. it was flown with aglow engine before but the mounts were falliing apart so I trying to fly it electric. it had throttle with the glow engine and was fun to fly when it was too windy to fly stunt .

Offline Jim Carter

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Re: what does a higher c rating do?
« Reply #8 on: January 12, 2022, 09:40:56 AM »
Here's something to understand. C rating is achieved by increasing the size of the internal conductors and the physical chemistry. A battery having a total amount of electrolyte, anode and cathode are capable of a specific amount of energy delivery. Watt x seconds or Watt hours. For a given weight you can parse that out in many ways depending on the internal conductors. Often times you'll see the same cell in two different batteries with two different  capacity and C ratings. When you take them and do the energy calculation you'll see they have the same Watt second capacity. What this means is that you will more than likely have to increase the battery size. No way around it. What you need to determine is how much battery you need in terms of Watt Hours. To do this you need to determine the power required on your next test. The current is only half the equation. It only tells you if the wires are gonna get hot including the ones inside the battery.

So you are trying to achieve a run of a given amount energy expenditure. You can calculate your Watt usage and time of flight to determine the energy capacity you need in Watt Seconds. Then from that you can determine how much storage you need and the C rating required. The specific energy of LiPo batteries very from 100 Wh/kg to 265 Wh/kg. Not knowing how long a lap is it's hard to say how big the battery must be.


So static power for that prop running 14 k is about 0.9 Hp which is 671 Watts. In flight at 100 MPH that power is going to drop down to 0.54 Hp and 402 Watts. Lets say the laps will take 5 minutes
 and the energy it takes to get up to speed is equivalent to one minute operation  6 minutes total or 0.1 hours. This means you need a minimum of 402 W x 0.1 hr = 40.2 Watt hours. Your battery and motor are matched for the 4s battery? It's important as the efficiency of the system will bite your effort if they aren't. Given that W= I x V and then current rating for you battery will be determined Icap = Whr / V. Since the previous calculation is solely what is required for the flight a 20% - 30% margin should to be added resulting in 1.2 x 40.2 = 48.2 W*hr.  Then the capacity Icap = 48.2 Whr / 14.8 V = 3.2 AH. Looks to me like you're gonna need that bigger battery.

Here's a useful data link to the 8 x 8 propeller in order to do some analysis yourself.

https://www.apcprop.com/files/PER3_8x8E.dat
WOW!!  Your analysis is incredible!!  Lord knows, I wish we were closer with you as a mentor and friend!  I applaud you, sir!!  H^^ H^^

Jim

Offline Matt Curtis

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Re: what does a higher c rating do?
« Reply #9 on: January 24, 2022, 08:24:19 PM »
So I went ahead and ran a 3200 4s 30c battery to fly the cosmic wind. IHad enough to fly more than 15 laps without over running the battery. I got 60 mph with the 8x8 prop and65 mph with a 9x7.5 glow engine prop. I ran throttle at 80% with 8x8 prop and 90% with 9x7.5 prop battery was at 70% after 11 laps voltage 3.9 something per cell so no damage to battery. battery and motor never got warm. Plane weighs 3 lbs 12oz. battery weighs 10.5 ozs. Flying at maybe 5300' watkins colorado.

Offline Matt Curtis

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Re: what does a higher c rating do?
« Reply #10 on: January 24, 2022, 08:25:36 PM »
Flew on a full charge for each flight.


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