EMAX 2204II Cooling

1

1251452

Well-Known Member
Hello everyone,

I am currently trying to build a new 4s racing quad. I've got the emax 20A blheli esc, but I'm looking for a motor. I think I have found a good one:
http://www.ebay.com/itm/171923349248
Does anyone have these motors? Are they any good? If not, any suggestions? I want the high rpm still, with the 2300kv. I'm planning to use 5040 props.

Thanks in advance,
1251452
 
Looking at the specs they don't seem very efficient or very powerful considering they are running on 4s. Check these out;

http://www.banggood.com/T-MOTOR-MN2204-1400KV-2300KV-Brushless-Motor-For-RC-Quadcopter-p-973284.html

They are much more efficient( longer flights) and produce slightly more power on 3s than the Emax does on 4s! 3s batteries cost less and weigh less than 4s as well. The Tiger Motor is one of the better motors out there. Your quad will fail long before these motors wear out. Whichever you get try some 5030 and 5035 props as well.
 
Thanks for your reply,

I am a bit of a noob here but, how do you determine the efficiency or power from the specs? Until now, I have been looking mainly at the rpm, amps, and thrust generated. Also, Tiger motors are pretty top of the line, and slightly out of price range. Is there a cobra or sunnysky alternative?

Thanks,
1251452
 
1251452 said:
Thanks for your reply,

I am a bit of a noob here but, how do you determine the efficiency or power from the specs? Until now, I have been looking mainly at the rpm, amps, and thrust generated. Also, Tiger motors are pretty top of the line, and slightly out of price range. Is there a cobra or sunnysky alternative?

Thanks,
1251452
Click to expand...
Good questions. For example, the Emax you are looking at is a good example of the chinese playing games. On the chart the seller shows, for the 4s/ 5040 prop, 10.7 amp draw( from your battery) to get 510g thrust. If you scroll down to the bottom of the page the manufacturer claims 440g max. When you continue on the sellers page he shows 158 max watts and 3.2g thrust per watt. That doesn't quite make 510g. Close, but not quite. These are obviously just made up numbers. They say "100% balanced, decreasing vibration to the minimum." Huh? Is it 100% balanced or not. Most of these cheaper motors require more power(4s as opposed to 3s) to fly racing quads fast enough to suit their owners. That's one reason they don't last long.
Anyway. You can look at amp draw( lower the better) and grams per watt( higher the better) as a measure of efficiency. Consider thrust as horsepower (speed) and for simplicity consider the KV as torque (power). That's why I suggested trying a couple different lower pitch props to let the motor spin up faster to compensate for the lower torque(KV).
The T-Motors will add about $23.00 to your cost. The Cobra about the same. The SunnySky, which is a great little motor as well, about $10.00 to your cost.
Use manufacturers specs whenever possible on the cheaper motors. If you only have the sellers numbers available then adjust them by %10 or %15.
Don't ever hesitate to jump on the forum and ask questions. The members and mods on here are the best folks you'll find in this hobby. They will always be happy to help. Sorry I got so long winded!:D
 
Thank you so very much for the detailed response! Lots of great info :) So the EMAX 2204s are bad. The tiger motors I've heard will handle 4s just fine right? Can you recommend some other motors? The sunnyskys sound pretty good as well. I've heard that "4s capable motors" have lower Kv in order to lower amp draw and temp. What is the relationship of Kv and power produced by the motor? Will a faster spinning prop produce more power, at what cost?

Thanks very much!
1251452
 
1251452 said:
Thank you so very much for the detailed response! Lots of great info :) So the EMAX 2204s are bad. The tiger motors I've heard will handle 4s just fine right? Can you recommend some other motors? The sunnyskys sound pretty good as well. I've heard that "4s capable motors" have lower Kv in order to lower amp draw and temp. What is the relationship of Kv and power produced by the motor? Will a faster spinning prop produce more power, at what cost?

Thanks very much!
1251452
Click to expand...
Wow! Let's see if we can do this one at a time. The Emax are not as good as the other motors. That's true.
The t-motors are not rated for 4s but could probably handle it for short flights. No real need too though.
I don't dabble in cheap motors so I don't know of anything less expensive than the SunnySky's that I would recommend.
I'm not sure where you might have heard that about "4S capable motors". Li-Po batteries are built on 3.7v cells wired in series to make more voltage. A 1s is 1 cell and 3.7v. A 2s is 2 3.7v cells 7.4v. A 3s is 3 3.7v cells and 11.1v. A 4s is 4 3.7v cells and 14.8v and so on. A 3s 2200mah 30c battery is 3 cells with 2200mah capacity and a discharge rate 30x2200mah.
KV is the number of revolutions the motor will turn at 1 volt. A kv2300 motor will turn 2300 rpm at 1 volt and will spin a small, high pitch prop fast to produce a lot of speed at the expense of lift and with short flight times. Ideal for racing. A KV400 motor will turn 400 rpm at 1 volt and will spin a large, shallow pitch prop slow to produce a lot of lift and longer flight times at the expense of speed. Great for big payloads like cameras.
The T-Motors for example, produce all the power you need on 3s while the Emax require a 4s battery to produce the same power. A 3s battery will give a noticeable weight savings(you will fly faster) and cost difference from using a 4s.
I fear I'm rambling again. I hope this was some help to you. Figure out the approximate weight of your quad and then post that and we can help you pick the best combination of motors and props.
 
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