On this page I’m going to be giving my opinion on the EMAX RS2205 motors and putting them head to head with the Cobra motor.

You can buy the EMAX RS2205 motors from here:

• 2300KV model from here
• 2600KV model from here

Indeed, any drone enthusiasts out there may well have heard of these motors as there has been a lot of talk around them recently on numerous drone forums. They sometimes take the name “red bottom” as the motor itself has a red shade on its underside. Regardless of this, both the 2300KV and the 2600 models weigh roughly 30g and look exactly the same from the outside.

However, its the inside where the magic happens…

I’m going to compare these motors to the Cobra 2204. The Cobra 2204 is roughly 5g lighter as it uses less metal on the base and the bell.

EMAX tell us that they used some different types of magnets on these motors (the 2300KV and 2600KV). Also, the new design contains “cooling fins” which restrict the coil temperature down by at least 30%.

To fill you in with some basic statistics, the motors have CW and CCW thread rotations and the motor wires are 20AWG.

These motors have CW and CCW thread rotations (optional on product page). The motor wires are 20AWG.

Here they are in comparison to the Cobra. You can tell immediately that they look bigger (and hence are slightly heavier.)

Unboxing The RS2205

Despite its lack of importance in flying the drone, I always love it when a company takes time to package their product up well. EMAX does this exceptionally well. The box comes equiped with 8 motor screws, 3 props nylon nuts and a handy hex key!

Take a look at the photos below to see exactly what I mean.

EMAX does a very good job in the packaging. And it comes with 8 motor screws, 3 props nylon nuts and a hex key.

EMAX RS2205 2300KV Motor

To be honest, I was very surprised with the performance of this motor. It was very efficient and generated much more thrust than the cobra in almost every test.

The tests used the following setup:

• ESC: KISS 24A Race Edition – Factory Settings
• Battery: Turnigy Nanotech 4S 1800mAh
• Voltage: 16.2V – 16.6V
• Turnigy Thrust Stand

EMAX RS2205 2300KV Motor Thrust Data

Props	%	Peak Thrust – g	Peak Current – A	Max Power – W	Efficiency – g/W
Gemfan 4045	50	148	2.3	37.3	3.97
	100	460	9.6	155.5	2.96
HQ 4045 BN	50	257	4.4	71.3	3.61
	100	647	19.3	312.7	2.07
Gemfan 5030	50	295	3.2	51.8	5.69
	100	790	15.0	243.0	3.25
Gemfan 5040	50	304	3.9	63.2	4.81
	100	880	17.8	287.9	3.06
Gemfan 5045	50	342	4.6	74.5	4.59
	100	938	21.6	349.9	2.68
Gemfan 5045 BN	50	395	5.0	81.0	4.88
	100	917	23.3	377.5	2.43
HQ 5045 BN	50	386	6.3	102.1	3.78
	100	989	28.6	463.3	2.13
HQ 5040×3 Triblade	50	411	5.3	85.9	4.79
	100	1050	25.0	405.0	2.59
Gemfan 5045×3 Triblade	50	417	5.4	87.5	4.77
	100	1155	27.3	442.3	2.61

The Gemfan 5045 Triblades prop were from BG $3.5 for 4.

Cobra 2204 2300KV Motor Thrust Data

At first I tested this motor with a Blue Series 20A ESC with BLHeli firmware. However, I was unable to collect enough data as the ESC simply under performed and thus I had to redo the test but with the KISS 24A ESC. The results are shown below.

Props	%	Peak Thrust – g	Peak Current – A	Max Power – W	Efficiency – g/W
Gemfan 4045	50	133	2.0	32.4	4.10
	100	429	8.9	144.2	2.98
HQ 4045 BN	50	235	4.3	69.0	3.41
	100	588	18.2	294.8	1.99
Gemfan 5030	50	265	3.1	50.2	5.28
	100	718	14.3	231.7	3.10
Gemfan 5040	50	296	3.5	56.7	5.22
	100	810	16.8	272.2	2.98
Gemfan 5045	50	315	4.4	71.3	4.42
	100	837	19.7	319.1	2.62
Gemfan 5045 BN	50	375	4.7	76.1	4.93
	100	865	21.0	340.2	2.54
HQ 5045 BN	50	369	6.4	103.7	3.56
	100	862	27.2	440.6	1.96
HQ 5040×3 Triblade	50	355	5.0	81.0	4.38
	100	875	22.1	358.0	2.44
Gemfan 5045 Tri	50	401	5.2	84.2	4.76
	100	947	24.4	395.3	2.40

EMAX RS2205 2600KV Motor

The 2600KV motor is designed for the 4″ props on a 180 mini quad frame. However, it also works really well with 5030 props and therefore I may use that setup on my next 5″ build. I’ll let you guys know how I get on with that!

The 3S LiPo with 5″ props also works well with this. However, I forgot to test it on 3S! Sorry guys 🙁 I’ll update this post later with the 3S results included. Also, if you have any props that are larger than the 5045, the draw will exceed 30A which is was not good for the 24A ESC I that I used for testing. Oops…

 

Props	%	Peak Thrust – g	Peak Current – A	Max Power – W	Efficiency – g/W
Gemfan 4045	50	189	3.4	55.1	3.43
	100	529	13.5	218.7	2.42
HQ 4045 BN	50	311	6.4	103.7	3.00
	100	776	27.0	437.4	1.77
Gemfan 5030	50	355	4.7	76.1	4.66
	100	990	21.7	351.5	2.82
Gemfan 5040	50	395	5.3	85.9	4.60
	100	1025	25.6	414.7	2.47
Gemfan 5045	50	430	6.2	100.4	4.28
	**100	1120	30.0	486.0	2.30
Gemfan 5045 BN	50	400	5.8	94.0	4.26
	**100	1074	30.0	486.0	2.21
HQ 5045 BN	50	496	9.2	149.0	3.33
	**100	915	27.0	437.4	2.09
HQ 5040×3 Triblade	50	435	7.0	113.4	3.84
	**100	1025	29.0	469.8	2.18

** ESC entered over-current protection at 30A before 100% throttle was reached, so that might not the true full throttle thrust.

Conclusion

Ultimately, it is clear to me that the RS2205 is a winner (buy it here). It is easily one of the best motors out there for a 5″ prop and therefore I defiantly recommend that you buy it. However, someone who desires a lighter setup (perhaps for FPV racing) will probably find 30g a little bit too heavy for their drone.

I would also like to mention that during the tests that I performed, the Cobra motor was notably warmer which implies that the RS2205’s cooling fins are working!