Lipo C Rating

rwilabee

Member
Does anyone have any suggestions on how to calculate the proper C rating when you are purchasing Lipos.

Thanks
Rich
 



Macsgrafs

Active Member
You can only go by the manufacturers specs. If they say for example 35-70c, then always take the lowest number. Let's give a few examples.

4s 4000ma lipo rated at 20c = 80A discharge
4s 4000ma lipo rated at 35-70c = 140A - 280A discharge

3s 2200 ma lipo rated at 20c = 44A discharge.
3s 2200ma lipo rated at 40c = 88A discharge.

The magic is get the highest rating pack your money can buy...35c - 95c packs rather than a 20c pack.

Ross
 

rwilabee

Member
So I guess I need to also find out what my amp draw is on my Hex. I have a amp/watt meter I can change the connectors on so they match the ones on my hex. Say I'm at 75 Amps would it make much difference between a 35C and 45C. Would I get longer run time from say from a 5000ma 45C than the 5000ma 35C or it just would be easier on the battery.

Rich
 

Macsgrafs

Active Member
So I guess I need to also find out what my amp draw is on my Hex. I have a amp/watt meter I can change the connectors on so they match the ones on my hex. Say I'm at 75 Amps would it make much difference between a 35C and 45C. Would I get longer run time from say from a 5000ma 45C than the 5000ma 35C or it just would be easier on the battery.

Rich

Hi Rich,

Firstly make sure you dont overload your amp meter, most only go up to 100A!!!!
Let's try another way. your hex has 6 motors all rated at 25A max. so if you were flying flat out, that would be a total of 6 x 25 = 150A.
A 5000ma 35C lipo will give you 175A, but a 5000ma 45C pack will give you 225A max draw. Now considering your motors could easily draw more than 150A for a few seconds, then the 45C pack is your best choice. Flying time will be the same for both packs, but the 45C pack will handle full throttle climbouts or emergencies better.

Ross
 

rwilabee

Member
Ross...

That makes perfect sense. Let me ask you another question. I'm running a Thunder Power G6 5000 4S 45C (525 grams) right now for 8 minutes of safe fly time. I could go to Thunder Power's 6600 4S 45C (700 grams) and I think I could get 10 minutes of safe fly time. Is it worth the extra weight and size or am I going to weigh the XAircraft hex down to much since it is only 550mm from motor to motor. I'm running 10 x 5 props. I probably got to big of motors by getting the Avrotos. Maybe I should have gotten the Tiger MT 2216 motors. My hex weighs 12.3 lbs with the 5000 battery. Besides asking about the batteries do you think I should change the Avrotos to the Tiger MT 2216 motors. I wonder if I would get better performance from the Tigers.

Thanks for the advice.
Rich
 

Macsgrafs

Active Member
Rich, I can't comment on your setup, but the 6600 lipo would be a good investment in my book, extra time & extra punch.
As for your motors, check out weight V's thrust & also power consumption to see what offers the best, but it sounds like you have a good setup as it is. If you don't mind me quoting what my setup is as a reference.
I fly a SJ8, using 8 x emax GT 2820/07 motors, each with 2.3Kg of thrust, I power these with 4 x 4s 4000ma 35-70C lipos...thats 16000ma (160A), my current draw flat is is calculated at 40A x 8 motors = 320A, running on 12x 6 APCE props.

Ross
 

rwilabee

Member
Thanks Ross....

I'm going to get one of the 6600's and see how it does. I'll leave motors and props alone for now.

Rich
 

rwilabee

Member
Hey Ross...

Here is info from my research.... I could only find specs for the Tiger at 11.1 so I'm comparing the Avroto at 11.1 also instead of the 4S that I have been running. These specs are for an 10 x 4.7 prop. I know my Avroto can handle the 10 x 5 prop at 4S the specs on the Tiger Motors say to drop to an 8" prop at 4S.

Thanks for your suggestions.

Rich


Avroto Motor Weight 100 grams - 11.1 volts - 14.68 Amps - 163 Watts - 862 Grams Thrust - KV 770

Tiger Motor Weight 75 grams - 11.1 volts - 12.7 Amps - 140 Watts - 1050 Grams Thrust - KV 900
 
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rwilabee

Member
Ross...

If I changed to the Tiger I could probably go to a 9" prop vs the 10" I'm running now since the tiger is a higher KV. I wonder if that would be better as I would have more distance between props since my Hex is only 550mm or do you think I would lose performance.

Thanks

Rich
 
Last edited by a moderator:

Macsgrafs

Active Member
Ross...

If I changed to the Tiger I could probably go to a 9" prop vs the 10" I'm running now since the tiger is a higher KV. I wonder if that would be better as I would have more distance between props since my Hex is only 550mm or do you think I would lose performance.

Thanks

Rich

Rich,
I think you will lose 2 things & gain 2 others. You will lose a touch on the stability & duration, but gain on response & acceleration.

Ross
 




xtakos

Member
So a 4S battery at 6000mAh rated at 25C discharge can constantly output 150Amp.Right?
How all these amp`s can be transfered through a connector that supports a maximum of 93Amp like HXT 4mm??

The battery i am talking about is the Turnigy 4S nanotech 25/50C.

Just a thought...
 

Macsgrafs

Active Member
So a 4S battery at 6000mAh rated at 25C discharge can constantly output 150Amp.Right?
How all these amp`s can be transfered through a connector that supports a maximum of 93Amp like HXT 4mm??

The battery i am talking about is the Turnigy 4S nanotech 25/50C.

Just a thought...

That battery will be fine, the 35-70c is a bit better for not much extra weight!

Ross
 

xtakos

Member
Well my question isn`t which battery is better.My question is how a battery can deliver 150 Amp through a connector that can only deliver only 93Amp??
And to extend that i am thinking of using 2 of these batteries in parallel.So, even if i use an EC5 connector that can support up to 120 Amp`s the total Amp`s that might be needed is a maximum of 200 Amp`s (8x25Amp).
How can i transfer all that Amp through any connector out there??
 

Macsgrafs

Active Member
Well my question isn`t which battery is better.My question is how a battery can deliver 150 Amp through a connector that can only deliver only 93Amp??
And to extend that i am thinking of using 2 of these batteries in parallel.So, even if i use an EC5 connector that can support up to 120 Amp`s the total Amp`s that might be needed is a maximum of 200 Amp`s (8x25Amp).
How can i transfer all that Amp through any connector out there??

~The connectors are quoting a safe operating current. Just like your car can do 120MPH, but the speed limit is 70MPH. When they say 93A, at what voltage is that rated?

Ross
 

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