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Old 10-22-2010 | 03:04 PM
  #29  
cat samich
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From: wakeman, OH
Default RE: esc selection help


ORIGINAL: NobodyFamous

240 is super over kill. I'd say the 180 is over kill.<div>
</div><div>Real quick for you. . Watts = Volts x Amps</div><div>
</div><div>The motor is what will ultimately draw as many amps as it wants, so start there.</div><div>
</div><div>Your motor's supper huge ultimate power output is rated at 3500watts</div><div>
</div><div>In a chart this means</div><div>
</div><div>2s (7.4V) x 472.97 = 3500 watts</div><div>3s (11.1V) x 315.31 = 3500 watts</div><div>4s (14.8V) x 236.48A = 3500 watts</div><div>6s (22.2V) x 157.65A = 3500 watts</div><div>
</div><div>Now given that you can put out 3500 watts at only 2s 7.4V the size of the wires required to handle almost 500 amps would be huge, and all efficiency would be lost. You would also have to swing such a huge prop because RPM would be so slow. It can be done though.</div><div>
</div><div>A quick guide.</div><div>Watts is equal to Horse Power, in the sense that it is a measurement of power. Power is what moves the boat (well work is. . .)</div><div>1 HP = 745 Watts</div><div>
</div><div>Watts = Volts x Amps, so no matter how you move electricity, via amps or volts, the combined output is the watts.</div><div>
</div><div>it is easier to move electricity in the form of volts, less loss occurs.</div><div>
</div><div>As for RPM, 30,000 is the goal. So your motor spinning at 15,000 RPM/V (1500Kv) will turn 33,300 RPM Just right. (these are all unloaded RPM)</div>

things are starting to make so much sense, the reason i plan to go with the 240 is so that i can switch motors if i want without worry. but if i read correctly from what you posted this motor may draw as high as 236.48 amps on 4s, which i may also decide to run. the 240 will handle all of that.

one last question, if the goal is 30k rpm and in a perfect world all of our boats turn 30k how are some of these guys getting boats into the high 60's and even into the 70's? any guesses on what kinda of speed i can look forward to? my goal is to pass the 50mph mark