High RPM motors - is it good or not?

[Sergey]

Hi!

I recently interested in EV scooters and found this website: http://www.superscootersales.com/. Website looks cheap though they claim to have best motors. Also their prices are a bit expensive. On this forum I just found a thread where I read that website refused to sell a replacement motor. This is weird, since I guess all of their scooters are from China where they sell tons of parts too.

Couple days ago I also recently found another website http://www.hyperpowersports.com/ which offers EV scooters for $549-$600. It's twice cheaper comparing to superscooters. But I tried to find the difference and I see that hyperpower uses regular battery which is not Lithium and motors are probably brushed. The owner told me they sell parts too. I found similar scooters online in China for about $300. You could probably by them for $200/each and bring a full container of scooters here.

But my concern is about battery and motor. I see that cheap scooters use lead-acid batteries which are heavier than LiPo and cost much less. But if battery is more or less clear, then motor seems to be complicated. I don't mind to have a brushed motor, but I worry about power and RPM. They don't provide any info about motor model number and about motor specs. Cheap scooters have 1500w motors, but I suppose that power as achieved at very high rpm.

I read that it's better to buy a scooter with power motors which deliver power at lower RPM.

For example, this brushless motor has 1500w, but very high RPM: http://www.ebay.com/itm/BRUSHLESS-MID-AXIAL-MOTOR-48V-1500W-CONTROLLER-E-SCOOTER-E-BIKE-QUAD-BIKE-CAR-/201060585451?pt=LH_DefaultDomain_0&hash=item2ed0250feb

So I wonder if such 5000-7000 RPM motors are good or not? At least in term of reliability comparing to low RPM motors.

 

[torqueboards]

I'm pretty sure for our application. Lower rpm / higher torque is way better for electric braking and acceleration. I've tried a few high RPM motors and they suck I've tried 400kv motors and didn't like them at all.

 

[spinningmagnets]

Awesome find. The stuff coming from China that is mass-produced is very cheap. The first vendor you mentioned apparently wasn't worried about competition, but now this new guy will apply some heat to the market. The 48V 1500W stand-up scooter is interesting.

With Sealed-Lead-Acid (SLA) batteries, the only person who wins is that the purchase price will be lower. They live such a short life, you will replace them three times in the ammount of time that a lithium-ion pack (not LiPo) would last. So...if you start with lithium, you pay a higher purchase price, but the batteries last much much longer. During the whole time they are lasting longer, they are also lighter for the same watt-hours of capacity.

When it comes to motors, get the biggest one that will fit, there is no substitute for copper mass. You can get more power density by switching to a higher-RPM motor and gearing it down to the same output RPM (with a bigger pulley reduction, or add a jackshaft), but if given a choice of a bigger motor with a single reduction, compared to a smaller motor that spins twice a fast and drives a2 stages of reduction (via a jackshaft), ...given that they would both have the same output at the wheeel...I would still choose the bigger motor.

If the motor is warm when you are using it during the hardest part of your commute, it is the proper size. Too hot and it will fail some day soon, too cold and you have chosen a motor that is larger/heavier/more-expensive than necessary...it all depends on the system design and the job that you are tasking the motor with.

 

[Sergey]

I think that SLA batteries are much much cheaper too. For example, a single 12v 10ah SLA battery costs about $20 on Amazon, thus a pack of 4 will cost $80 comparing to several hundred bucks for a 48v 10ah lithium battery back.

Unfortunately, I don't know anything about motors in that cheap scooters, but I wonder if there is any good and proven motor which is worth buying to swap the default motor?

I was able to find only a few replacement motors:

1) First is MY1020 which is 1000w brushed motor. This motor is 150mm x 108mm.

http://www.ebay.com/itm/MY1020-1000W-48V-UNITE-DC-Electric-Brush-Motor-With-Mount-Bracket-/160925248200?pt=LH_DefaultDomain_0&hash=item2577e46ac8

2) Second is unknown 1500w brushless motor. This motor is 125mm x 107mm, so it's a bit smaller than 1020:

http://www.ebay.com/itm/BRUSHLESS-MID-AXIAL-MOTOR-48V-1500W-VAE-E-BIKE-QUAD-BIKE-CAR-e-SCOOTER-/190895253816?pt=LH_DefaultDomain_0&hash=item2c723e6938

Any better proven motors?

I found some other motors, which are more expensive, but that motors look a bit different, thus I don't know if they will easily fit in such scooters.

Yup, in order to check the temperature of the motor I have to buy a scooter first. I think I'll pass by that place (hypermotors) during next week to check the motors. That guys are located here in Miami too.