Review – Emax RS2205S 2300KV Motors

by Oscar
Published: Last Updated on

In this review we are testing the new RS2205S 2300KV motor from Emax. With better magnets and design from the previous version, we’ll find out how they perform.

These motors are provided by Emax for the review. This article is written by Grzegorz Piotrowski.

What is special about this motor are the arc magnets and the consistent tight gaps between stator and the bell (on regular motors, the gap can change due to position between stator and motor bell – magnet). This makes the magnetic field more consistent and provides better/faster throttle response.

One thing I was worried about was that mud and sand could get stuck inside the motors. This wasn’t the case, the gap is so tight that no mud or sand could get in so far.

Emax has shaved 2g off these motors from the original version. In terms of temperature, I only found it a bit warm with DAL 5045×3 props in my testing, but I haven’t noticed this during regular flights.

Spec

  • Manufacturer: Emax
  • Line: RS – S
  • Stator size: 2205
  • Physical size (height x radius): 28.42mm x 27.96mm
  • KV: 2300
  • Weight: 28-29 g (stock wiring)
  • Material: 7075 Aluminum + hollow steel shaft
  • Lipo rating: 3-5S

Appearancee

The RS2205S Motor comes in a nice plastic box together with 1 x propeller lock nut and 8 x M3 mounting screws. I love the Emax motors boxes, I often reuse them to store screws and stuff.

The RS2205S is very similar in appearance and build quality to it’s predecessor, the “redbottom” RS2205 2300KV. Motor bell and base are made of 7075 aluminum, it’s very cleanly cut, the coils are also wound up nicely.

The Motor has strong arc magnets, I could feel the resistant when spinning the motor by hand, and the it stops very quickly.

The biggest change I can see is the removal of “C” clip – it has been replaced by a screw in the bottom of the motor shaft. In my opinion it’s a better solution than C-clips. However I’ve read that someone had a problem that this motor shaft screw got loosened mid flight – their recommendation was to use loctite. In my case i didn’t use it, and so far (I’ve had around 50-60 packs with these motors), they haven’t fallen apart yet. From my perspective this one feature alone would make me jump on those motors… but the increase in “power” is a much more important reason for me to get them.

The shaft in this motor is hollow, which should improve the motor shaft strength and reduce weight.

Thrust tests

These tests were done with 4S 16V LiPo.

Below you can find thrust measurements of other motors I have tested in the past with the same equipment (a DIY thrust stand), as comparison:

Note: this time I had to conduct this test on a different ESC – the Racerstar MS35A.

Props % Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W
KingKong 5040 50 364 5.8 98.2 3.71
100 1257 30.1 483.7 2.60
Gemfan 5040×3 50 441 6 103.4 4.26
100 1327 29.58 479 2.77
Gemfan 5045 HBN 50 442 6.2 104.8 4.22
100 1375 30.3 485.3 2.83
DAL 5045×3 HBN 50 488 7.21 121.9 4.00
100 1440 35.87 572.3 2.52
Racekraft 5051×3* 50 459 7.31 121.9 3.77
100 1313 50.61 810.4 1.62

* In my bench tests with RaceKraft 5051×3 propellers, the data was showing they were drawing too much current at full throttle. However I love how the RaceKraft props perform in my outdoor flights with the RS2205S motors. They have so much punch that saved me many times from crashing into the ground, which I probably couldn’t pull off with DAL 5045×3 HBN.. Having said that, you should check what works for you, and use whatever your are comfortable with.

Verdict

Pro’s

  • Good quality motor
  • POWER!
  • Short spin up time – as the motor magnets are strong the reaction time is very short
  • It was not getting hot even on RaceKraft 5051 – looks like cooling is more than enough
  • Tight tolerances – engine not blocked after crash with dirt
  • Arced magnets -> consistent gap size -> more power

Con’s

  • Prop nuts attached to this motor are of mediocre quality. they can be easily stripped, I would recommend getting some separate ones
  • One of the shafts/nuts combination didn’t want to work – I’ve changed the nut it is better but prop needs to be pushed a bit harder to get in place. I’ve noted this only on one motor
  • Battery “ripper” – they can drain your battery very quickly if you will fly aggressively.

I’ve been trying to “kill” these motors for about two months, they perform brilliantly and I really enjoy flying them. The reaction time is much better than any other motors I’ve used so far.

They had no problems with spinning very aggressive props like the RaceKraft 5051, and while flying on the lighter KingKongs 5040 it was very smooth.

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18 comments

Max 11th May 2019 - 2:45 am

Hi Oscar, thank you for the review.
With the new laws in place requiring weight to be below 250 grams to avoid all restrictions, I was wondering how would this perform on 2s ( for a model airplane.) The prop ideally would be 6×4 / 7×3 / 8×4 electric, and thrust around 300 grams would suffice.
Any suggestions on motor choice are welcomed. I do not want to go more than 3s to avoid battery weight.

Reply
Morg4n 1st January 2019 - 11:05 am

Hello,

thank you for the review,
Have them since a week and I don’t now why but any HQ Prop I tried on them didn’t fit properly. I have to apply a lot of strengh to push down the propeller on the motor…And if i have to change the props it’s a pain to take them out of the shaft of the motors, really!!!

Any idea what kind of prop i might use to get them installed easily? Why is this happening?

Reply
Oscar 1st January 2019 - 12:29 pm

I think you posted on the forum too, I replied there.
http://intofpv.com/t-propellers-dont-fit

Reply
huseyin yildiz 7th January 2018 - 3:56 pm

hello . i am a big fan of you from Turkey

i want to thank you for work.

can you suggest me prop size for 5s for Rs2205 s 2300kv,

Reply
Oscar 8th January 2018 - 3:25 pm

4S? I like running 5040 – 5045 triblade on motor of this size

Reply
Stiven Bunger 17th July 2017 - 4:01 pm

how come on the emax website they say its 3-4s ? WILL these run with a 5S or no? did you test that ?

Reply
Oscar 24th July 2017 - 3:40 pm

quite a few friends of mine have. but it’s not recommended so people are doing it at their own risk :)

Reply
Barnabas 16th May 2017 - 8:19 pm

Another newbie’s question connecting to this: will my battery be unusable if I go little bit above the maximum allowed C rating? (1.4 battery with 80C max discharge=>112A; and this motor with 33amps x 4 motors=132A)

Reply
Oscar 18th May 2017 - 12:48 pm

Your quad still still fly don’t worry.
If the battery can’t deliver the current it will simply run at lower power and suffer voltage sag. And for a short time period like a few seconds this is not an issue.

Reply
Ahmed 29th April 2017 - 8:41 am

Hi dear
I would like to know if you measured the maximum allowable acceleration of this motor.
I mean that what is the time required to reach its maximum speed from rest?
Thanks
Ahmed

Reply
Chris 27th March 2017 - 2:51 pm

Are the prop tests in this article on 3s or 4s? Seems like a pretty important bit of info to leave out!

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Oscar 3rd April 2017 - 6:25 pm

4S :) thanks for reminder updated now.

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seth 14th March 2017 - 1:07 am

are the shafts replaceable, i have bad luck with hollow ssshaft motors

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Oscar 24th March 2017 - 12:08 am

you might have to replace the whole bell, shafts are not removable from the bell.

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Britton 22nd February 2017 - 12:07 am

This site is great. Thanks, sincerely.
So, I’m starting to build my first proper FPV/acro quad, and I’m just having a hard time figuring out compatibility. Or as much, what math needs to be done.
I was actually planning on using these motors on a 210/5″ quad setup, with a 3S battery and 30A ESCs (that’s enough, right?). I’d really like to run a 3S setup for weight, but I don’t want a 2 minute flight time. Would this power/motor combo be bad?? Or is there a better motor you could think of for the setup.
I’m obviously new, but I’d like components that could grow as I do as a pilot.

As a follow up, most of the places I’ve seen recommended a naze32 FC, but this site seems to have argued against that. Would a beginner notice the differences in a more modern controller.

Thanks for any feedback and keep up the good work.

Reply
marcus 6th June 2017 - 2:07 pm

You will not notice any benefit of this big motor on a 3S and a 5″ prop. If you want to make a light build with your 210 frame and a 3S, you can safely go with any reputable brand 2205 2600kv motor and a 20A esc to pair your 11.1v lipo. That will give you more than enought power and quick response to start with as your quad AUW will be under 400g (with a ~100g lipo, ie 3s 1300mah).

Reply
Jeffrey 8th February 2017 - 7:41 am

Hey Oscar, i have a noob question on which i cannot find the answer to. I truly hope you can help me on this one.

The question is really simple. Is every ESC compatible with every FC. I ask this because i already ordered my moters and esc’s. (Emax RS2205S + Bullet D-SHOT’s 30A ) i ordered these as a set. So would these work with for example a Kombini?

Now i dont want to order a non-compatible FC. I would be truly greatfull if i could get some in depth info regarding this, besides youre reviews are awesome!
Kind regards, hope to hear you soon ;)

Reply
Oscar 8th February 2017 - 12:07 pm

it’s gets a bit more complicated than that.
firstly, find out what ESC protocol your ESC uses.
secondly, find out what FC firmware your FC can be flashed, and if that firmware support the ESC protocols of your ESC.
Most of the time this is not a problem, but with DShot, Betaflight supports it, but Raceflight and Cleanflight currently don’t.

Reply