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5s / motor

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rcaddict02/11/2019 09:56:29
530 forum posts
2 photos

would i get away with using a 5s lipo (25c) on a motor rated at 2-4s, motor is 3536 1200kv, (i dont have any 4s right now)

Dickw02/11/2019 10:06:59
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720 forum posts
99 photos

Using 5s rather than 4s means the motor would try to run approximately 25% faster and draw a lot more current. You would have to use a much smaller prop to keep the current down to acceptable levels. You would then need to make sure the motor (and the prop) were safe at this higher rpm.

Not a good idea unless you know exactly what you are doing.

Dick

Jason-I02/11/2019 10:11:47
318 forum posts
43 photos

Others more knowledgeable may give you a better answer, but I would say it is possible, by several methods.

1) Using existing prop, limit throttle travel on 5s so that you do not exceed 4s rpm and current draw values.

OR

2) Re-prop accordingly so that you do not exceed maximum current rating of motor and ESC.

 

3) I am no expert. Wait for others to comment.

Edit: Dick beat me to it.

Edited By Jason-I on 02/11/2019 10:12:46

rcaddict02/11/2019 10:11:47
530 forum posts
2 photos

yeah i can prop it down and the esc would be ok my worry is if the motor could handle the voltage, i would not need full throttle

Edited By rcaddict on 02/11/2019 10:12:32

Jason-I02/11/2019 10:15:28
318 forum posts
43 photos
Posted by rcaddict on 02/11/2019 10:11:47:

yeah i can prop it down and the esc would be ok my worry is if the motor could handle the voltage, i would not need full throttle

Edited By rcaddict on 02/11/2019 10:12:32

Voltage is unimportant. It's the max current that matters. Also, don't forget that the throttle controls the voltage - hence limiting the throttle would limit the voltage.

Edited By Jason-I on 02/11/2019 10:17:14

Dickw02/11/2019 10:20:07
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720 forum posts
99 photos

The motor would have no problem with the voltage - it is current and rpm that are the problem with motors. The manufacturers voltage ratings (recommendations) are aimed at ensuring sensible current and rpm are achieved in practice with normal sized props.

The ESC should be rated to at least the expected full throttle current even if you do not intend to use full throttle. The ESC does not limit current, it pulses it, and part throttle is harder work for an ESC thna full throttle.

Dick

rcaddict02/11/2019 10:33:27
530 forum posts
2 photos

55amps on a 10x6 - esc is 60a - will drop down to 9x6 !!

Dickw02/11/2019 10:44:06
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720 forum posts
99 photos

You need to measure the results with a decent meter in some short test runs before deciding if it will be OK and what prop to use.

I would have said that a 10x6 was for 3s, and a 9x6 for 4s. For 5s I think an 8x6 would be a goood prop to begin tests with.

55 amps seems quite high for a 3536 size motor.

Dick

Edited By Dickw on 02/11/2019 10:47:53

Alan Gorham_02/11/2019 11:01:19
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1287 forum posts
145 photos

I agree, for example the Turnigy Sk3 3536 1200 is rated for a max current of 38A. You might be on a sliding slope of reducing the prop size so much to keep the current down that you don't get enough thrust to fly the model.

Be interested to see where you end up..

Simon Chaddock02/11/2019 12:19:53
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5715 forum posts
3034 photos

Voltage is a real limit for the ESC components but not so much for the motor.

Provided the load is kept within the maximum specification amps (amps alone dictates the heat generated) the voltage is not a issue although at some point the motor will start to suffer from the higher rpm, likely the bearings first or at extreme rpm it could throw a winding.

The winding insulation can also break down but you are up to many hundred volts before that is likely.

The manufacturer sets the advised limit at 4 s as the life of the motor is likely to be acceptable as far as warranty claims are concerned. wink 2

Even keeping the same amps the motor at 5s will develop about 30% more power but as Gordon points out smaller higher revving props are less efficient so you won't see all of that extra in flight but with the same battery weight the flight duration will decrease by at least that figure, if not more! smile o

Edited By Simon Chaddock on 02/11/2019 12:22:07

Frank Skilbeck02/11/2019 15:59:04
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4730 forum posts
101 photos

As the motor will be turning quicker a 9 x 5 prop might be a better bet.

Also check your ESC while most are good for 6s batteries, some are only rated for upto a 4s.

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