# When is a motor too big?



## 3dplane (Feb 27, 2008)

Hi Norm! Sounds like you did some homework on motors I think you already answered your question by stating "motors are most efficient when run within their designed voltage /current range".So think about it: You use a very large motor,chances are its best efficiency is going to be when its pulling very large amps that leads to big power.So the vehicle now is going really fast, the batteries are sweating, the aerodynamic drag ripping the roof off,BUT our motor is at its best efficiency...do you think the overall efficiency is good?Probably not.I hope this wild example did not confuse you,but i think the motor size just have to be a good match to the vehicle and its application.Cant be too small(burns up) cant be too big(rips your roof off)/joke/Thats not counting the extra weight and space.I hope someone here can explain better. Barna


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## ngrimm (Oct 19, 2007)

Thankyou for the reply. Maybe a better example of what I mean would be say running two or more dc forklift motors in parallel in an EV closer to the 36 volts they were designed for instead one at two or three times that voltage. Maybe a better question would be: where is the biggest efficiency loss of the EVs entire electrical system? Am I correct in assuming it is the losses due to heat in the motor when it is over powered? Once again I appreciate your help. Norm


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