Scooter speed vs needed KW's hub motor?

[dutchlincoln]

Hello,
currently, i want to modify a electric scooter, and am lloking around for different type's of controllers.
To start with the base, wich is the hub motor i guess, is how much power is needed?
The most common chinese scooters are equipped with 750W or 1500W 48volts brushless motors.
now, i'd like to know what speeds are possible with these motors?
I would aim for 40-45 Mph. Is this achievable?

Another Q.
How do i determine my continuous power needed for my controller?
Kelly sells nice controllers, and have different continuous amp. ratings.
I would aim for 100A continuous, in order to have enough headroom. ( low volts, hot weather, maybe a hill, or something like that.)
When i read correct, the Lyen 24fet controllers are stock 60 amps, so it's as good as twice the power...

Is there a good way to connect a cycle analist to a kelly?

Anybody can chime in and give me some info?

Thanks.

[John in CR]

Those scooter motors with the built in rim run around 16rpm per volt no-load. That's the 1500W version. The 750W is probably more like 11-12rpm/volt and won't be able to handle nearly the current. About the best you can expect on flat road no wind is 75-85% of the no-load speed. Regarding the controller, 60A battery side is a pretty good number unless you have hills or pushing too much weight.

Feed that 1500W model with current and voltage and you can have a fun little vehicle as long as you keep the weight low. I use a similar motor in a 14" rim that works out to a 20" diameter wheel with the tires I have, and my 120lb bike with 250lb me will do right at 60mph with a long enough road and me tucked down as much as possible. I use 74V nominal and fed with 75A or more it's a fun workhorse with solid passing acceleration anywhere between 20 and 45mph.

If I had it to do over again some of the 5 motors I got would have been with 10" rims instead of the 14" and 17" rims I got. That's because the smaller the wheel, the greater the torque for better hill climbing and acceleration with less heat issues. You can always make up the difference by going to a higher voltage.

[gge5]

At 45MPH my hub motor scooter takes about 4500 watts (~62 amps at 72 volts) to maintain speed. 35MPH is about 2KW, and 25MPH is 1KW.

Most of the Chinese scooters that have <1KW hub motors are limited to 20MPH.

You'll have to find the Kv rating of your motor to determine how fast it's capable of going at your pack's voltage. Most hub motors range from 10Kv to 18Kv. You multiply the Kv rating times your battery voltage to find maximum RPM. Is this a 10 or 13 inch motor? An 15Kv motor with a 48V battery pack and a 120/70-10 (10 inch) tire would max out at about 35MPH, and you would have good power up until about 28MPH (80% of the top speed).

If you're looking to go 45 MPH you have a couple options:
A 13 inch, 18Kv motor with a 130/60-13 tire and a 48V pack
A 13 inch, 14Kv motor with a 130/60-13 tire and a 60V pack
A 10 inch, 18Kv motor with a 120/70-10 tire and a 60V pack

As far as choosing a controller:
Say you have a 1500 watt motor, rated for 48V. That means it can handle about 31A (1500/48) continuously. Electric motors are rated for their continuous current handling abilities, but I drive my hub motor 3 times this rating during acceleration. So for this motor you're looking at a 100A, 48V controller.

[gge5]

The cycle analyst doesn't connect to the controller. It attaches to a shunt between your battery pack and the controller. The CA can tap into one the hub motor's hall effect sensors to measure speed. I use shielded Cat-5 networking cable to run the signals from the shunt to the CA.

[dutchlincoln]

Okay, thanks for the tech explanation. Nof finally i'm starting to understand where Kv stands for.
Is there a way to determine this value for a motor?

Is it truly every 10Mph double the power???
That's a lot.

Now, as you say yourself, the motor can take up to 3 times the rated power.
Does this mean i can get the power/speed given of 4500 watts with the motor that is officially rated for 1500 watts?

Also, at kelly they state a equal motor, one optimised for speed, the other for torque. What is the technical diference between the two? Is this the hall timing?

The 100 amps in your example, is this a continuous value? (the kelly controllers give cont. & peak power ratings.)

When i choose a 72v controller, can i (for the time being) run it on 48v until i upgrade my power source? ( naturally, in the software i would need to specify min/max voltage and maybe some other things.)

Currently, i have an option on some used LiFePo's 50ah, 19pcs, making approx. 57 volts. Not sure on what to do yet... I will open a separate battery topic.

[gge5]

Okay, thanks for the tech explanation. Nof finally i'm starting to understand where Kv stands for.
Is there a way to determine this value for a motor?

If you can find a motor performance chart, find the top speed and divide by the motor voltage.

Is it truly every 10Mph double the power???
That's a lot.

It goes up exponentially, so the difference between 15 and 25 MPH is not nearly as much as 35 to 45MPH. Motorcycles are less aerodynamic than cars so wind resistance begins to really affect them at about 35MPH.

Now, as you say yourself, the motor can take up to 3 times the rated power.
Does this mean i can get the power/speed given of 4500 watts with the motor that is officially rated for 1500 watts?

Only for short bursts. On my scooter I use the extra power for acceleration from a stop, generally less than 5 or 10 seconds. Anything longer than about 30 seconds and you possibly risk melting the lamination on the motor's windings and cause an internal short. Some motors have temperature sensors which can signal the controller to send less power.

Also, at kelly they state a equal motor, one optimised for speed, the other for torque. What is the technical diference between the two? Is this the hall timing?

This is the Kv rating, and is determined by the number of turns of wire in the motor. A lower Kv will give you a lower top speed, but more torque/acceleration. This is the tradeoff of a hub motor, since you can't switch gears.

The 100 amps in your example, is this a continuous value? (the kelly controllers give cont. & peak power ratings.)

No, the 31 amps is the continuous rating, but the motor could briefly handle 3X that.

When i choose a 72v controller, can i (for the time being) run it on 48v until i upgrade my power source? ( naturally, in the software i would need to specify min/max voltage and maybe some other things.)

Yes, it should be able to run down to 24V. Kelly provides some free software to interface your computer to their controller, but you will have to buy a USB to RS232 cable to be able to program it. I got mine at Deal Extreme for under $5. When the 72V controller arrives at your door it will have a default 60V LVC (low-voltage cutoff) enabled, so you'll have to reprogram it to accept your lower pack voltage.

Currently, i have an option on some used LiFePo's 50ah, 19pcs, making approx. 57 volts. Not sure on what to do yet... I will open a separate battery topic.

19 Cells is pretty non-standard. Common packs are 16, 20, 24, and 32 cells. You may have trouble finding a charger for 19 cells.

[gge5]

I'm starting a business building electric scooters, Escape Velocity Electric Vehicles. After a lot of research I came up with the configurations of a couple of models.

The one that can go 45MPH has this configuration:
24 Thundersky 40Ah cells, 72V, 200A Peak
Kelly 4.5kW High-Torque motor, 72V, 190A Peak
Kelly KEB72601 Controller, 72V, 200A Peak

This specific motor is 11.5Kv. The tire is 130/60-13 for a circumference of 60.14 inches. At 72V the absolute top speed is 47.2, but in real use it's about 40 since acceleration drops off dramatically as you approach the upper limit for your voltage due to back-EMF.

At 35 MPH it gets about 58 Wh/Mi, for a usable range of a bit over 40 miles.

[dutchlincoln]

Ahhh..., i read about that one indeed! nice!.

Thanks for the (very clear) explanation.

I had my eye on the same controller, so that's a good choice i guess

Also, what is (besides the 2 LED's) the main difference between the kelly KEB and KBL controllers?
They state the KEB to be highly efficient due to high PWM frequency, but i believe the opposite is true?

Also, in the past i heard about complaints of Kelly's making a lot of motor noise, is this true?

19cell is unusual indeed. Maybe i have to buy one (new) extra...

thanks.

[gge5]

The KBL line has a longer pulse current rating of 1 minute, whereas the KEB can hold maximum output for 30 seconds before throttling back. This is fine for the 4.5KW motor, because pushing that much current through the motor for an entire minute would burn it up. I'm not sure if there is a physical difference between the components. We've used have both KBL and KEB controllers. They both weight the same, so that rules out a larger integrated heatsink. That leaves either higher quality components, or simply a software setting. We use a 1/4" aluminum backing plate with some thermal adhesive to assist in keeping the controller cool.

The KBL also has a CAN-BUS (You'll notice it has a second circular plug on it for this purpose). A CAN-BUS might be useful in a car, but not on a scooter.

I've found that the motor selection makes more of a difference in noise than the controller. There is a firmware setting for "less sound", but it lowers power output as a side effect. There is a bit of a rumbling below 5MPH, but above that it's a nice quiet whine.

[dutchlincoln]

okay.
I'm leaning a bit towards the hub motors from kelly also, but i think they're quite pricey....
Are there other (good) sources for HUB motors?

i have 10" now, but i'd like to have 13". (more stable)
I have to measure if it fits though.

[gge5]

You're pretty limited as to where you can buy motors individually. Kelly has always been great. You could inquire at chennic.com or evmotor.net (Yangzhou Keguang).