Thread: New Product Change Sun 10 blade 70mm
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Old Jul 23, 2012, 09:53 AM
PeterVRC is online now
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Australia, VIC, Melbourne
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Not '40C'.... but 174 Amps capable. (5800mAH 30C)

C is not that useful a rating, mentioned on its own. I would prefer to see a number quoted as "Capable Amps", which then makes the actual battery capacity and C rating irrelevant.
In these tests all you really want to know is what did the motor WANT to draw, and that the tester had more than that capacity available, because if you know that then you can work out what issues you will have when you use it in any other battery combo.

eg A combo tested 'properly' used 70 Amps, running from "200Amps capable", giving 2.0Kg thrust, so that means the motor was unimpeded in attaining the best it could do (whether that means it was run way over specs or not is not important here). Any other person that runs that test, with adequate Amps available, will get the exact same result (within a tolerance range). Because that is what that motor's physical construction, and KV rating, will drive a CS10 in every case that it is given adequate source current (Amps).

And a person with a certain aircraft, and certain batteries they already own, might see they don't even want 2.0Kg... so their first best choice is not to use that motor combo at all. They really need less KV to lower the RPM and thus thrust. They can also do the maths on their battery... hmm, it is "90Amps capable", due to its small size and C rating, and thus they will know that the motor WANTS 70A and it is pretty assured their battery will never truly give that out (the stated battery ratings they put on them are dream numbers! LOL), so if they still chose to use that combo it would suffer from voltage sag, and it would run weaker than that 70A test case.... maybe even fluking the lower thrust they wanted to have, but it would be damaging their battery in that process. The only reason it runs lower output, lower RPM, is because the motor load dragged the battery down which means bad for it.

If someone tests a motor on inadequate current capability, then those figures are not a lot of use to anyone (almost). Because it is not what it can truly do. Just what it did on their inadequate battery, which would have sagged X amount, been bad for it, and just under-quoted that combos true ability.
Even more useful is to do TWO tests.... one with more than enough current capability, to show the true maximum. And then using a typical battery people would probably want to use in such an application - that is because in the majority of these cases people ARE using batteries not truly up to the job of what they are driving. Because to have the truly adequate battery is too heavy for any aircraft the combo is used in. (when we are talking in these high end number regions - not an issue for lower output combos)
But you need the 'capable current supply' test to show what the true MAXIMUM need would be. Then you can say "Well I am getting 60A, and X sag, and the battery is X temp... and I know it would run to 70A in an adequate system, so my battery is 'this' far off that ability. Using higher C, or larger capacity, to have 10A more capability would be more correct so as not to damage the battery.".

There are a few other factors that come into play in it all (ESC, wiring), but not really important, beyond that outline above.
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