E-bike lover said:1.Are the windings diferent between 36v and 48v motor?
Yes; they are different between 36 & 48v versions. The different wattage options are all the same hardware though, it's only limited in software with the stock firmware.
E-bike lover said:2.How does 48v battery works on 36v motor? Will the power exceed 250W? I have seen that if a 48v battery being used on a 36v motor, u could have more speed. Is it 30% more? If i use a 48v battery on 48v motor, the speed will get lower but more torque. What is the maximum speed?
The stock firmware will refuse to work with wrong battery voltage.
On the OSF firmware, the maximum power can be limited to whatever value (watts) you want, irrespective of what motor & battery voltage combo you have installed.
With a 36v motor and 48v battery, you can have higher cadence at the cranks, which does not necessarily mean higher speed (at the wheel). With the "correct" combination of motor and battery, it stops assisting well at around 75 - 80 rpm at the cranks. If you want to pedal faster than that, then the 36v motor, 48v battery combo is useful - with that you can pedal at up to 120rpm if you want.
Again, this is referring to speed at the cranks (cadence) - with 48v motor and 48v battery, you will get "normal" cadence, and "normal" torque at the cranks. With 36v and 48v, you will get a motor that can go to higher cadence, and less torque at the cranks, so you have to pedal faster to get the same amount of power in the end (higher speed / cadence but less torque = same amount of power). Some people want to pedal faster, hence getting this combo. How this affects the final speed at the wheel depends on the gearing of your bike.
However, now the OSF has a kind of "overdrive" mode giving you assistance up to 120rpm even on "correct" motor and voltage combos, IIRC it's a bit inefficient in that high cadence rrange.
E-bike lover said:3.Can i speed up my bike(over 25km/h) while my battery is 48v but the maxium support power in motor is only 250W?
In the OSF firmware, you can set speed and power limits to whatever you want, independently. So you could set unlimited speed and 250w if you wanted. Although with 250w I don't think you will go much faster than 25 - 30kph anyway, no matter what your motor and battery voltage combo is (maybe there are differences in gearing and efficiency, but I think 250w is 250w, and should give you about the same speed in the end)
E-bike lover said:4.There is a bluetooth function on SW102. Is it able to update the firmware via app or website? Or is it still developing?
I know a bit programming in website.
Link from github doesn't mention:https://github.com/OpenSource-EBike-firmware/TSDZ2_wiki/wiki
You can update the firmware of the sw102 itself via bluetooth and app (that's the only way to do it), however the motor itself still has to be updated via computer (with stlink), and since they both have to have the same version you cannot update everything over just buetooth, so you still need computer. It's theoretically possible if someone implements it, I think.