dutchlincoln wrote: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.
dutchlincoln wrote: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.
dutchlincoln wrote: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.
dutchlincoln wrote: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.
dutchlincoln wrote: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.
dutchlincoln wrote: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.
dutchlincoln wrote: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.