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Old Jan 12, 2013, 01:32 PM
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chopper52's Avatar
United States, MI, Cedar Springs
Joined Sep 2008
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Need Advise on what C rating for this system set up!

Hi Guys
Need some exspert advise on what C lipo to use with this system I have!!!
I have a 90mm Wemotec Pro 6 blade fan,,,1700kv (8s only) Velocity motor,,,,Ice 100amp esc...I know I need to stay under 100amps..I was going to use 2 times
4s 5000 lipos...What C should I use???? Thanks Guys......
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Old Jan 12, 2013, 02:09 PM
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Maxthrottle's Avatar
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Joined Jun 2009
6,663 Posts
The formula you decide with is what delivered amps do you need.
Sorting out the fact first:
What will the motor demand. That setup, if memory serves peaks at 90 amps demand but for the sake of quick understanding say its an even 100amps that it will need. You would know the actual amp demand of that setup.

Any battery you choose has a certain capacity, e.g. your 5000mAh battery.

You shouldn't as a habit use the last 20% of capacity so from that battery you're using 4000mAh.


e.g. Demanded Amps/(capacity mAh/1000)=C rating.
100amps/5amp=20C

HOWEVER (this is the mistake many make) Note, you're getting that 100amps off a fully charged battery. As you fly it will deplete down to 1000mAh at which point a 5000mAh 20C depleted to 1000mAh is that only delivering 20amps.

So you decision is how long to you want to fly delivering 100 amps.
Because you don't control your rating they just come in 25, 30, 35 40, 45, 55, 65, 100C
You get the following
Cap| Usable| 20%| A@ 20%| C| OutAmp| Mx Load| “Est.mAh fall off”|
5000 4000 1000 20 20 100 100 5000
5000 4000 1000 25 25 125 100 4000
5000 4000 1000 30 30 150 100 3333.33
5000 4000 1000 35 35 175 100 2857.14
5000 4000 1000 40 40 200 100 2500
5000 4000 1000 45 45 225 100 2222.22
5000 4000 1000 55 55 275 100 1818.18
5000 4000 1000 65 65 325 100 1538.46
5000 4000 1000 100 100 500 100 1000

So depending on how hard you want to push it for the duration of your flight, and considering that you should be off the throttle periodically the 45C and up is typical for many pilots looking for all around flying.
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