Instructables

What's the difference between volts and watts in an electric scooter motor?

I'm hoping to build my own electric scooter in the summer once I know more about the motrs, batteries, etc I've found two 500w electric motors on eBay. One's 24v and the other's 48v. what's the difference? why would they need different voltages? I can't remember that particular lesson about electronics from my school lesson lol.?

rickharris3 years ago
voltage is a measure of the electrical "pressure" required by the motor.

Wattage is a measure of the power it consumes.

Essentially Watts is Volts x Amps. So as Steve says for the same wattage but different voltages one motor will draw proportionally less current than the other.

Worth noting that 500 Watts is 2/3rs of a horse power, (about 746 watts to 1 horse power), This is quite powerful for a small scooter - if we both mean the same thing - And 4 batteries is twice the weight of 2 - in most electric vehicles weight is the most critical criteria and battery weight the most easily controlled. BUT make sure the wiring is up to the greater current required at 24 volts.
JustusH14 days ago

Is it possible to join a alternator to an electrical 500w motor, where the 12vx12amp battries are joined in series, giving 36 v off. Do i need to change the alternator and how, to be able to load the battries as if it is loaded via an electrical 220 v charger ?

Who can tell me and where can i go to get it done, Boksburg in RSA. Thank you all.

MOT-E100sm.jpg500w Motor 2.jpgFOIB7KOH6735FHS.SQUARE.jpg
JustusH14 days ago

Is it possible to join a alternator to an electrical 500w motor, where the 12vx12amp battries are joined in series, giving 36 v off. Do i need to change the alternator and how, to be able to load the battries as if it is loaded via an electrical 220 v charger ?

Who can tell me and where can i go to get it done, Boksburg in RSA. Thank you all.

MOT-E100sm.jpg500w Motor 2.jpgFOIB7KOH6735FHS.SQUARE.jpg
JustusH14 days ago

Is it possible to join a alternator to an electrical 500w motor, where the 12vx12amp battries are joined in series, giving 36 v off. Do i need to change the alternator and how, to be able to load the battries as if it is loaded via an electrical 220 v charger ?

Who can tell me and where can i go to get it done, Boksburg in RSA. Thank you all.

MOT-E100sm.jpg500w Motor 2.jpgFOIB7KOH6735FHS.SQUARE.jpg
JustusH14 days ago

Is it possible to join a alternator to an electrical 500w motor, where the 12vx12amp battries are joined in series, giving 36 v off. Do i need to change the alternator and how, to be able to load the battries as if it is loaded via an electrical 220 v charger ?

Who can tell me and where can i go to get it done, Boksburg in RSA. Thank you all.

MOT-E100sm.jpg500w Motor 2.jpgFOIB7KOH6735FHS.SQUARE.jpg
JustusH14 days ago

Is it possible to join a alternator to an electrical 500w motor, where the 12vx12amp battries are joined in series, giving 36 v off. Do i need to change the alternator and how, to be able to load the battries as if it is loaded via an electrical 220 v charger ?

Who can tell me and where can i go to get it done, Boksburg in RSA. Thank you all.

MOT-E100sm.jpg500w Motor 2.jpgFOIB7KOH6735FHS.SQUARE.jpg
JackIsted (author) 3 years ago
These are all great answers, thanks. So am I right in thinking that a fully charged 48v system will run for longer than a 24v system? if of course they do the same journey running the same person. (I can see that the extra 2 batteries aswell)
Vyger3 years ago
To get 24 volts you would wire 2 12volt batteries in series. To get 48 volts it would be 4 batteries in series. So with a 48 volt system you are committed to using 4 batteries just to get the voltage to run your motor. Also the higher the voltage the more careful you have to be with insulating. 24 volts will not give you a shock but 48 could if your hands have something conductive on them.

A quote from a physics forum.

"A few years ago, the automotive industry decided upon 40V as the maximum safe voltage for human exposure; this is still well below the threshold of sensation. The minimum voltage required for sensation depends on specifics like skin moisture, but is usually above 60V.

Obviously, the mucosa presents a much lower resistance than does the skin; you can quite easily feel 10V placed across your tongue, for example."

So 48 volts is still in a safe range but you do need to be more cautious with it. Something like a big scratch or an abrasion could get you a jolt if you contacted the power source.
Personally I would go with the 24 volt simply because of the number of batteries involved. If the 2 batteries wired in series couldn't give you enough amps you could add a second set of 2 so you would have what amounts to 2 24 volt batteries. But to double that with 48 volts you would need to go from 4 to 8 batteries. If this was for a car or a large 4 wheeler I would go with the 48 but because its a scooter where the battery carrying capacity is more limited I would use 24 volts.
One takes twice the voltage, and half the current to deliver the same power. It depends on your battery stacks. More voltage is a good thing, if you can fit it in the space available.