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Nov 08, 2017, 09:01 AM
Registered User
Discussion

Amps


How mutch do you think about Amp draw when shopping for motor esc combo?
I see the 2300kv emax red bottoms draws around 33a at full tilt with 5045 prop. Im running this with a 30a esc just fine for now.
But im rearly at full throttle for wery long..
Should i have used a 35a esc?
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Nov 08, 2017, 11:45 AM
Registered User
You'll be fine, people run 30a escs with my motors and they can pull 45 in static tests. First, static tests generally use more power than in air max, second as you said most people don't use max often, third batteries do provide some minor level of protection when every motor is trying to draw max at the same time however a single motor can still pull max easily.

I like to break it down like this, if you go over spec within reason you'll probably be fine, but if the motor ever stops rotation under power during a crash it will almost instantly blow the ESC.
Nov 08, 2017, 01:47 PM
Registered User
Ty! Thats what i was thinking.
Nov 09, 2017, 02:15 AM
Registered User
Please, can you show me such test ?
Curious to see what was the setup and how were measurements done... by all physics in this part of universe, I don't see how a 5" prop can load a motor in this class to deliver 500 W power...
Even for 33A, you must use a 70 grams 3500kv motor to reach this draw.
All the simulations were done for 4s.
Nov 09, 2017, 03:50 AM
Registered User
Suteki's Avatar
Quote:
Originally Posted by renatoa
Please, can you show me such test ?
Curious to see what was the setup and how were measurements done... by all physics in this part of universe, I don't see how a 5" prop can load a motor in this class to deliver 500 W power...
Even for 33A, you must use a 70 grams 3500kv motor to reach this draw.
All the simulations were done for 4s.
Miniquadtestbench.

EngineerX does some reviews on youtube, check the amp pulls on these;
BrotherHobby Avenger 2507-2700KV - Marvelous Super Powers! (20 min 26 sec)



Newer motors regularly hit 40+ amps, some of the bigger ones 50amps on some props.

Its a static test though, so its 'worst case scenario' of and based on burst and no way indicative of actual in flight numbers. Worst scenarios for amp pull;

- motor loaded up on test bench
- going from zero to max throttle when quad is dropping straight down
- in a hair pin when the quad is accelerating back against its own momentum.

30a is heaps of headroom. For most pilots the battery wont sustain that output of 100amps or more for more than a few seconds anyway.

If you were routinely hitting above 30amp your quad must heavy as a brick or you are massively over powered.
Nov 09, 2017, 03:58 PM
Registered User
Ok, will watch and count how many physics laws they break
Any propulsion calculator will tell you that a 5" prop, to draw such amount of power should have a rpm that will evaporate it, even carbon. So, somewhere should be a cheat...
Nov 09, 2017, 04:19 PM
Registered User
What the heck are you smoking Ren. Maybe you forgot that air resistance is exponential not linear.
Nov 10, 2017, 04:30 PM
Registered User
A Gemfan 5045 prop, to draw 40 Amps from 4s, i.e. 600 W power, must be turned with 35k RPM. And the thrust of this hypothetical setup would be 1300 grams.
And surely 600W can't be delivered by a 30 grams of iron and copper...
The above is a fact, I trust more this computation than any smoke crack breath these testers in your face.
Feel free to demonstrate otherwise if you you don't believe it.
Now show me the Gemfan prop able to be turned with this ludicrous speed... never wondered why these thrust "tests" don't include also a RPM meter, that will disclose the truth ?
Nov 10, 2017, 06:33 PM
Registered User
I use Dal cyclone 5050's with a emax2306's 2400kv at 5s. That amounts to about 50k rpm at max output. In fact, it draws so much power that my 1300mah 80c, 160c burst battery will drop down from 21 to 14 volts and risks a low voltage shut off if i draw maximum output for more than a few seconds on a perfectly fresh battery. And yes, the output thrust for ONE of my motors is about 1300-1400 grams and it flies over 100 mph.

Lets take a look at the results for the emax 2750. http://www.miniquadtestbench.com/ass...fo.php?uid=131

Oh look, 5x4.5x3 props draw 40 amps almost on the dot, and it goes up even higher for 5 inch props depending on the design. It's easily possible, quit being silly. You're purposely ignoring actual tests based on some theory you have in your head.


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