I am looking for a formula to predict top speed of a scooter based mainly on motor wattage. You can assume the rider will be under the limit of the scooter and that the "gearing" (sprockets) are reasonable so as to not lug the motor at nominal voltage but also not so low as to spin the motor higher than normal at its nominal operating (rated) voltage.
Here is an example. My Mongoose M200 scooter (from 2007 I think) is normally 24V and tops out at 12 MPH (using the standard 15 and 90 tooth sprockets). I overvolted it to 36V and now it goes 18 MPH (confirmed) using the same sprockets.
Question is, had I not overvolted (either by choice or cuz it would not work), but instead upgraded the existing motor which I think is either 180W or 200W, what wattage motor (at say 24V) would I need to match the increase to 18 MPH? Would I need a 360 to 400 watt motor? If so, does that mean my little 180-200 watt motor is now putting out double its rated power (from about 1/4 HP up to maybe 1/2 HP, 1 HP = 746 watts)? Do you need quadruple power (in watts for example) to double the top speed? For example, if my original motor was 200 watts and went 12 MPH but I wanted to go 24 MPH, would I then need 800 watts?
My question was not answered. For this particular question, you can further assume that different wattage motors have the same nominal RPMs, so that we are just taking wattage as a yardstick for top speed. So for example, if my current motor is 200 watts, 2500 RPM, 24 volts, and can propel my scooter up to 12 MPH max speed, how many watts would I need to double my top speed to 24 MPH? Assume the 24 MPH setup has a motor that is also 2500 RPM and the "gearing" of that scooter is "double" to compensate for the increased power. That is, the weaker motor will push the scooter 12 MPH at 2500 RPMs and the more powerful motor will push the scooter to 24 MPH also at 2500 RPMs.
Oh I see now! In your case, with a very low-powered electric scooter, you will want to double the wattage of the motor, along with making sure the rest of the electronics can handle it, to safely double the top speed with a bigger or smaller sprocket. You will still get a doubled top speed even if you don't replace the motor and if you change the sprocket, but it would be very bad for the motor. I recommend you double the motor wattage to avoid having to replace the motor all the time. If this still doesn't answer your question then I will just back off and let ESP Support answer your question a whole lot better (I am only fourteen and modding a Razor GFD Fury).
Doubling the wattage will likely not double the top speed. Until someone else has proof of otherwise, I will assume that to double the top speed, a quadrupling of motor power is needed. For example, if a 200W motor can propel a scooter up to 12 MPH, then to propel that same scooter up to 24 MPH, an 800W motor would be needed. This is assuming both motors are sprocketed to put them in their "happy" RPM range (not oversped and not undersped).
I am confused. How come that calculator doesn't account for the most important information like a motor's rated RPM and the sprocket/gear sizes? Was David James correct about everything he said? Was I wrong about anything I said? I want to know because I might have this twisted reality that is wrong about motor power and top speed potential for my mod.
Motor speed and sprocket sizes are not part of the input parameters or result of the motor power calculator so it can focus on estimating the top speed that a motor can be geared for. Once the top speed is determined by the motor power calculator then our top speed and gear ratio calculator can be used to determine which motor and sprocket sizes to use.
Due to so many data parameters being required to determine what speed a motor can propel a scooter to there was not enough data included in any of the above comments to assess if they are correct or incorrect so we suggest using the motor power calculator to estimate what size motor to use for a specific top speed.