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Old Jan 22, 2013, 07:36 PM
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Fast maybe, but with a 4400mah lipo probably not the longest flights. Now if your just gonna cruise around you'll get a lil more flight time.
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Old Jan 22, 2013, 07:55 PM
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Originally Posted by goldsworthy View Post
So, From what I read here I should do rather well with the two 4400mah 6S 65~130C Lipo Packs I got.The SU35 should go fast with a C rating of 65-130
"Look Mamma, I'm goin fast"! "Faster?" not really. Your motor demand is your motor demand. So WW's 25C still delivers the needed amps as your 65C. The only slight difference is you'll likely see a little less voltage drop at the beginning allowing rpm/kv to rpm a little faster.
Where your 65C has an advantage is it will deliver the max amps right to the last 1538mAh of capacity. After around 3-3.5 min even hard flying, will it start to drop off to about a max deplete of 880mAh pushing 57amps.

Mixed flying you'll confidently fly around the same 4 min as WW but where he wins is weight. His batteries weigh less. Where you win is you worry less in that 4 min no how bad you fly and you can push harder pretty much for that 4 min without LVCing.

If you fly with energy management, you aso have more margin for go around.
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Old Jan 22, 2013, 08:01 PM
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The "Motor demand" isn't actually the motor demand for different batteries.
A higher C battery has a lower IR (Internal Resistance), so the "voltage divider" of volts over motor and battery are different. Higher C = more motor volts. Equals more Amps.... equals more power.

A made-up 'typical' table of motor volts - just to demonstrate what happens:
65C 22.3v
45C 21.7v
35C 21.4v

All of them degrade as capacity goes down, but the higher C is always going to be that bit higher volts (per depletion amount) than lower C's.

The bit Max mentions about LVC is true.... because the Lower C batteries volts hit a lower point sooner than higher C's do. Even lower C's could hit LVC before even depleting 50% capacity. eg A non Nano 20C, or even 30C - because non Nano have even higher IR than equiv spec Nano.

For any given motor/fan combo, you won't know all the finer details of the battery's results in volts, and degrading levels, until tested.

There is also no way those 25 Nano's are going to compare to 65C Nano's !! That is a huge capability difference, and 25C is very low and weak for this use!
For a start it is physically impossible... mathematically impossible... and I also have tons of battery testing experience, and it is impossible! LOL
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Old Jan 22, 2013, 08:09 PM
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5000mAH 25C = 125A "capable"
5000mAH 65C = 325A "Capable"
They never truly do what they claim AND maintain rated volts.
You need at least 1.5x the "Capabiltiy" typically, to have a battery that can maintain decent volts.And really more towards 2x.

So the Su can use 110A off a good battery... so it needs to really be 170A capable at least. Preferably 200A+

Those 25C Nano's would be lucky to maintain 22.2V even within seconds of running. (not truly sure of that battery and how long - but it wont be long).
Even 65C won't for overly long, but still much longer than 25C ever could.
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Old Jan 22, 2013, 08:18 PM
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25C continuous discharge rating for 5,000 mAh LiPo at 101 Amps. I'd like to see your math as You haven't convinced me Pete.

Maybe I wasn't clear in my earlier post, but I have not hit the LVC yet. Not when flying at full throttle even with my mediocre 25C rated batteries and definately not from depleting my battery capacity to the LVC area.

Would someone else post their stock configured power measurements? I think your numbers would not be far off, if anything maybe a few Amps off. My fans are dynamically balanced by myself, so there's room for a little less load.
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Old Jan 22, 2013, 08:57 PM
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Originally Posted by Whiskey Whiskey View Post
25C continuous discharge rating for 5,000 mAh LiPo at 101 Amps. I'd like to see your math as You haven't convinced me Pete.
25c x 5ah = 125a max, as you fly a lil longer 25c x 4ah = 100a, 25c x 3ah = 75a ... see where this is headed? As your flight time goes up you mah go down, thus your motor demand from your batteries remains, but your batteries cannot deliver that. This is why we have suggested 40C batteries for this plane if you wanna push it.
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Old Jan 22, 2013, 09:02 PM
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I would have to agree Pete based on my very next sentence. I guess it should be It is pushed as hard as it is pushed?

One issue with the way your charting that is its anecdotal at best.
The C count is created by various means in a chemical paste. So the voltage variance changes from batch to batch and brand to brand. There would be little useful or reliably linear pattern to work with. I can still by a cheap crap high C battery and get a high voltage drop under load. My C rating my still deliver a certain amps for a moment or some may base the rating strictly on the IR but once the paste is fired up it doesn't deliver. That's why there is so much variance even within a brand let alone differing ones. Thats why you can have true equal C counts but the fall off can be very different.

And Ah, 0.3-0.5V difference between C counts how do you jump from 90amps100 buffered peak even with 65C batteries to a 10amp increase pushed to the motor? The mAh consumption under such are indiscernible when it comes to mAh capacity consumption.... A pilot could add an extra hard bank or one less and not notice a difference.
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Old Jan 22, 2013, 09:19 PM
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I couldn't make sense of that last paragraph Max, but anyway...

Yes, there are variations in battery brands and what they claim etc.
But a good rule is "NONE do as they claim", LOL.
So you use the maths off the specs, hoping you might get that... but TESTING tells you what any given application will give.
And in the end, Lower C equals lower performance.... almost assured. (rare cases of some surprisingly good battery)

Put a data logger in the plane and see what it does... (or even a long run on a bench logging it all).
But I can assure you now that NO 25C matches a 65C !!! LOL. Even the 'luckiest" of those rare cases" would not! And especially as they are the same brand/manufacturer.

Even the 35C Nano's are much better than the 25C's. The 25C's ARE the 'failed the test" 35's. Well, they are identical battery sizes, so that shows they were the same cells.
They would just IR test them during manufacture... not current load test them at all.... and place them into 'bins' of the IR, to be assembled as the appropriate C then.
I doubt they would ever load test even one single battery again, once the initial design was made. It burns the storage goop.... and adds a big waste of time to manufacture anyway. No need. Via IR is easier and close enough anyway.
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Old Jan 22, 2013, 09:28 PM
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Whiskey, Its been posted in the thread even with 65C batteries no one reported over 100 amp stock. We've been using it as a loose base line. That could easily go lower with connectors and gauge.

Pete's not wrong that with higher C rated batteries there "usually" is a [slight] voltage increase. That increase in voltage can turn the motor at a [slightly] higher rpm and thus demand [slightly] more amps. However as I just said the its minimal and varies with brands recipes.

The difference in voltage with C rating is fractional which should tell Pete, with so little a voltage increase to the motor, the amp demand isn't going to greatly increase with the same curve that you see with mAh/1000xC Rating. A 25C may only deliver 125amps, but the 65C 1 volt increase is by no means using all the extra amps, 325amps deliverable of the 65C battery.

Lipos are not power plants with some form of stable output. They are a chemical reactions. Just like the wifes cookies, sometime they are good, other times they ar really good. When your lipo pushes out a settled voltage, that motor then needs the amps to match it. But the amps supplied is also dependent on the capacity so when you get the same performance of 100amps to the motors because your Nano is still pushing out enough volts, it pushes that 100amps with its peak number which we know can only be done in short burst or the cooky starts to crumble.

You're doing the right thing not to push it hard past the 3.5 min and that is why your 25C is performing. Longevity varies with the brands recipe. Nano has changed theirs twice now to the abuse and recovery may change but going by averages it is on this basis that we keep saying your at the margin especially going into 4 min. With the higher C the recipe is more resilient though the end numbers are not marginally wider because the voltage output isn't marginally wider.
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Old Jan 22, 2013, 09:35 PM
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Voltage differences between cells.... I guess that comes into part of how one battery can be different to another (same specs), but it is a minor aspect.
The IR is the bigger factor. Capable of making quite a notable difference to volts over the motor.
And higher volts means more Amps.... and Power is Volts TIMES Amps, so it is a double whammy of power increase!! (or loss).
eg You don't just lose "0.5v", you lose that AND Amps that caused it to run lower at. You can lose 100W, 200W, and more, easily.

Followed then by a sharper volts drop off as capacity/time goes by. So it gets worse and worse.... and become more an more important as the flight goes on.
Less power..... hotter battery.... making it even less power (more volts drop)....

That all doesn't mean you MUST use higher C.... because you can find good 'balances' of lower C applications. It means you need to TEST things in YOUR application and manner of use, and see if it is appropriate or not. Power sustainability... heat... flight time.... how much money you have.... (to buy an adequate battery, OR repair a plane, LOL).
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Old Jan 22, 2013, 09:38 PM
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My 65C can maintain 22,.2V long term
My 30C can't even do 21.5v from the start! Going sub 21v in short order.
And the power results are NOTABLY different.
It is not some small negligible difference.
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Old Jan 22, 2013, 09:38 PM
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If the increase in volts between C rating differ so little, the amp demand with the increase in volts isn't going to increase significantly. But you post 110amps. No one has even with high C count and even Hyperion batteries have been able to push these much past 100amps. The ESCs are rated to 55amps but the extra is buffer. So I wasn't clear if that was an embellishment to sell the need for high C ratings cause with the higher C there is higher volts and thus higher amp demand etc. Thus I didn't get how you have this jump.

I agree with you to a point there usually is a slight voltage increase at first with higher C rated batteries. But its not much and it doesn't last long.
What drops off more notably is as you near the end of capacity low C vs high C rating. high C has a very short drop off with similar capacities.

Quote:
Originally Posted by PeterVRC View Post
....the Su can use 110A off a good battery... so it needs to really be 170A capable at least. Preferably 200A+...
Quote:
Originally Posted by PeterVRC
65C 22.3v
45C 21.7v
35C 21.4v
OOOwww we're in it now Circle the wagons Ma!
You no how to do the numbers. .7v difference isn't going to suddenly increase the amp demand. And regardless of IR not in theory, the delivered amps out is still 125amps for his 25C. So with .7V more the demand goes up what another 2-3 amps; not even.

Couple that with that entire math discussion in the CS70/10 thread and you can see the marginal increase in delivered watts, isn't a huge jump to thrust and efflux numbers. Its there, but not with some huge leap.
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Old Jan 22, 2013, 09:40 PM
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Originally Posted by v8truckin View Post
25c x 5ah = 125a max, as you fly a lil longer 25c x 4ah = 100a, 25c x 3ah = 75a ... see where this is headed? As your flight time goes up you mah go down, thus your motor demand from your batteries remains, but your batteries cannot deliver that.
Now this I was unaware of. I had thought that the discharge ratings were based on the max capacity of the pack, not on the actual charge in the pack as it depletes.

I'm going to research that some, it sounds reasonably plausible to me. Are you sure you aren't being mislead as the voltage steadily decreases throughout the discharge and then steeply drops when it nears full depletion?
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Old Jan 22, 2013, 09:51 PM
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But.... the Su will fly "OK" on the 30C's (mind you mine are HET2W30s in CS10s - more demand than stock). "OK" meaning nothing amazing, and quite different to the 65C Nanos.

From all the other various battery Cells, C's, Capacities, I have.... I see the 25C Nanos are towards a 30C, maybe 35C, non Nano type battery. Certainly no more than that.
And the 35C Nano's are clearly better than the 25C ones (I have a few capacities in 4S of both).... it is like the 25C's were the 'rejects' of the Nano family. They fly with less power, and get much hotter - even puff if not careful - than the 35C versions of them.

Whether a $110 65C is better than a $70 30C, in your own use/application, is up to your assessment - but it certainly won't be anywhere near the same performance - from start to finish. And as long as the 30C isn't driven to be overly hot (via high current demand OR large capacity depletion) that is acceptable.
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Old Jan 22, 2013, 09:57 PM
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Originally Posted by Whiskey Whiskey View Post
Now this I was unaware of. I had thought that the discharge ratings were based on the max capacity of the pack, not on the actual charge in the pack as it depletes.

I'm going to research that some, it sounds reasonably plausible to me. Are you sure you aren't being mislead as the voltage steadily decreases throughout the discharge and then steeply drops when it nears full depletion?
I posted it a moment ago but it is the depleted number. That's why if you put a run up on with a watt meter, you start seeing amp die off quicker than the volts.

The magic is in the recipe and the peak number given. They have continuous rating and peak. If you are pushing a lower C rating to perform like a higher rated C battery, you are doing so in the peak values. Peak values are not continuous. The paste starts to boil off if you strain the peak and progressively risk damaging the chemistry of the cells. It usually comes in the sign on one cell starting to drop off quicker than the rest.
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