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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › C rating opinions
05-09-2013 04:06 PM  6 years ago
rexxigpilot

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Good point Richard. The ability of a battery to deliver electrical current is a function of both C rating and pack size. A 4,000mAH, 40C pack should theoretically have the same ability to deliver current as a 5,300mAH, 30C pack.
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05-09-2013 06:37 PM  6 years ago
3kidzheli

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It's only recommended for a 3300mah for the swift.There is no such thing as up, it's all out...
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05-09-2013 09:20 PM  6 years ago
3kidzheli

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6s on the way!There is no such thing as up, it's all out...
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05-09-2013 11:01 PM  6 years ago
doorman

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Question??? Can Always Learn Something New!!!
Good point Richard. The ability of a battery to deliver electrical current is a function of both C rating and pack size

OK, I read this and got lost:confusedthat is not a stretch!!!)
So what you are saying is running 2x 4s in parallel will reduce the need for a higher c rated battery???
I have always gone by the higher the voltage 2 x 4s in series to raise the voltage would reduce the amperage, so it fact that would be an 8s set up...But MAH on hand could be lowered to gain the same flight time??
Could you explain your suggestion (in laymen's terms) so that I can understand what your post better...

Looking forward to learning something new!!!!

Thank you, Stan

3kidzheli, I am not trying to highjack your thread.. but I think that the clarification will do us all good...
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05-09-2013 11:12 PM  6 years ago
fenderstrat

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Doorman what exactly do you need clarification on?your post is not very clearCompass helis Support Team
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05-09-2013 11:24 PM  6 years ago
3kidzheli

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No no not at all I'm a learner I like a debate especially one to benefit from! Go right ahead!!! There is no such thing as up, it's all out...
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05-09-2013 11:42 PM  6 years ago
doorman

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Question?
My question is for clarification of more mah means less c rating needed? The two posts from the uk
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05-09-2013 11:52 PM  6 years ago
fenderstrat

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C rating is determined by the capacity and stated ability of the cells to deliver amps.Examples are 20C 30C ect.C meaning the capacity of the battery.So a 20C 3000mah(3 amps)battery is rated to deliver 60 amps continuous(20x3).At the same time a 30C 2000mah battery will also deliver 60 A cont(30x2).A 30C 3000mah battery can deliver 90 Amps while a 30C 5000mah battery will deliver 150 AmpsCompass helis Support Team
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05-10-2013 04:17 AM  6 years ago
BobOD

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Just to add,
two 6s5000mah 40c packs in series is same as a 12s5000mah 40c pack. Series connection the voltages add, mah do not add and c rate does not add. This pack can deliver 200 amps.
200amps * 44.4volts = 8880W

Two 6s5000mah 40c packs in parallel is same as a 6s10000mah 40c pack. Parallel connection the voltages do not add, mah do add and c rate does not add. This pack can deliver 400 amps.
400amps * 22.2volts = 8880W

Two packs of equal size in series or parallel can deliver exactly the same amount of power and the batteries won't even know the difference.
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05-10-2013 05:16 AM  6 years ago
DougPenhall

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For some reason they made up this C rating unit that means 1C can handle being completely drained of charge in one hour. 2C can be drained twice as fast, or in 1/2 hour. 3C in 20 minutes. 60C in one minute. To drain a 5000mAh battery in one hour requires you to draw 5000mA from the battery for the entire hour. To drain a 1000mAh battery in one hour you would draw 1000mA. That would be 1C for both batteries. 2C would be twice the current for each battery and they would both drain in 1/2 hour. Everything the others said is correct and based on this definition of the C unit.
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05-10-2013 06:06 AM  6 years ago
fenderstrat

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this site is a must read for anyone into elec helis.Just about everything you need to know about batts chargers charging and much more.VERY good read

http://www.tjinguytech.com/charging-how-tos
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05-10-2013 03:38 PM  6 years ago
steve9534

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yakima, wa.

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Kidz heli
Please don't use a 6 cell lipo pack with your current setup as you'll overspeed the thing and possibly kill yourself. The main gear on your heli is 96 tooth and the pinion you've not stated. The smallest pinion you can theoretically use is 8 teeth, but I was unable to actually find one smaller than 9 teeth. Even if you have the 9 tooth pinion, the gear ratio will be 9/96 or 10.67:1. A 6 cell pack gives about 21 volts under load which means your 1450KV motor will be turning close to 30,000 RPM. If the motor doesn't fail at that RPM, the head speed will be approximately 2800 RPM, higher if you happen to have a larger pinion. Century doesn't recommend you go over 2000 RPM head speed with this heli and you run the risk of catastrophic failure if you try. My first electric heli was a Swift. I had no clue about cell counts, KVs, or head speeds and threw the t/r off the thing first. I repaired it only to have one of the main blade holders break and the helicopter literally explode in front of me. The guys are correct in that 4S doesn't work well with a 550 size heli, but you can't fix the problem by just putting in a 6 cell battery. Trust me on this one. You'll need a motor with a lower KV rating or you run the serious risk of catastrophic failure and personal injury. When mine failed,the rotor blade missed me by inches as it flew past and tried to embed itself in the side of our house. Be careful out there. Steve.
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05-10-2013 03:56 PM  6 years ago
DougPenhall

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Fenderstrat, awesome site. Thanks.

Steve, if the esc can handle the voltage, can't he lower the head speed by lowering the throttle in his controller? He could start with say, 50%, attempt to fly, then gradually increase it until he achieves his desired performance keeping in mind that he should stay away from 100% throttle since that would over speed his rotor blades.
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05-10-2013 04:08 PM  6 years ago
3kidzheli

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My bad I did not mention that I also bought several diff pinion sizes just incase I tried a 6s. Thanks for the warning as some people might know those important details! Thanks!There is no such thing as up, it's all out...
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05-10-2013 04:12 PM  6 years ago
3kidzheli

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Limiting the motor speed from the start was my first intention! Good idea! Wasn't sure what it would be. Got some diff of opinions on head speed calculations from some guys, by gear ratio, voltage, said that simple math would not be accurate. Plan to start out at 50%. There is no such thing as up, it's all out...
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05-10-2013 04:51 PM  6 years ago
3kidzheli

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If the throttle is max 80% then won't the flight time increase???There is no such thing as up, it's all out...
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05-10-2013 05:27 PM  6 years ago
DougPenhall

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I'm pretty sure there is an optimum rotor speed and blade pitch that maximizes flight time. If you go above or below that, your flight time will decrease. I'd be willing to bet that increasing the rotor head speed above the maximum flight time speed improves performance. Therefor, if the recommended maximum head speed is 2000 rpm, decreasing it should increase flight time until you reach the maximum flight time. You would have to experiment with different head speeds to figure out where that is, and come up with the best compromise between performance and flight time that is acceptable for you.
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05-10-2013 05:56 PM  6 years ago
3kidzheli

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Accomplished through diff throttle curve settings...There is no such thing as up, it's all out...
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05-10-2013 06:01 PM  6 years ago
JKos

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While decreasing headspeed will increase flight time in general, you also start to lose efficiency in the ESC and motor. The ESC will start to get too hot. ESC and motor temperature are you're limiting factors when dialing down the headspeed.

It's much better to reduce headspeed with gearing then reduced throttle. However, if you dial down the headspeed and your ESC and motor temps are ok, then it is ok.

Reducing throttle to force a 6S battery into a 4S kV'd/geared setup is quite suboptimal.

- John
RR rules!
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05-10-2013 06:27 PM  6 years ago
3kidzheli

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I know I'm beating a dead horse, BUT, since the motor kv is so high I have and a 4s simply
ain't enuf cellage, (no pinion come in kit) why would they even suggest a 4s battery....
There is no such thing as up, it's all out...
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