Help needed for my first E bike

[PVK]

Hi, guys.
I'm trying to build my first E-bike (to go to work and back) and I need a little assistance with it (maybe not so little). I decided to build mid-drive one with RC motor and Maytech VESC 4.12 controller. And the questions began.

1. I picked up Turnigy Aerodrive SK3 - 6374-168KV Brushless Outrunner (looks to be good rated). The max voltage is 44.4V (12S lipo battery). So the battery voltage must be about 36V (minus 8V for safety). And this leads to 8 or 10 cell lipo battery. VESC can handle with 60V.
2. VESC can handle safely with max 50A continuous current (max current for the motor 70A). If I set VESC to 45A, the motor power will be 10cells x 3.7V/cell x 45A = 1665W or 70% of the motor's max power (2400W).
3. If the battery discharge rate is 25C continuous than the battery must has about 45A/25C x 4 = 7200mAh.
4. Now the gear. For the primary reduction I want to use HTD 5M-15 belt with 16T/48T pulleys. For second, chain with 16T/52T sprockets. The motor RPMs are 168 x 37 = 6216 rpm. For 26" wheels this will be about 35 MPH. I expect average speed to be about 15-20mph in the town.
But if I use "Wye" wiring they will be 6216 / 1.7 = 3660 rpm. For the same speed and same primary reduction ratio, the secondary will be 16T/32T. I think that the "Wye" wiring looks better.

Am I right or wrong?
Is this configuration going to work?
Is this VESC good option?
Is it good to use battery with bigger discharge rate (like 65C/130C Turnigy)?

Thanks in advance.

 

[amberwolf]

1. I picked up Turnigy Aerodrive SK3 - 6374-168KV Brushless Outrunner (looks to be good rated).

What does "good rated" mean?

The max voltage is 44.4V (12S lipo battery). So the battery voltage must be about 36V (minus 8V for safety). And this leads to 8 or 10 cell lipo battery.

BLDC motors don't have a max voltage in that sense. Controllers do. So what you're needing is something that will spin that motor at the speed necessary to go with the gearing you are going to use to drive the wheel size you have with it, to reach the max speed you want, and also to still have the torque you need to accelerate at the rate you want and/or climb your hills / push against winds you have.

If the motor has an RPM limit your voltage might cause it to exceed, you'd need to have a tachometer on it that prevents the controller from exceeding that.

If I set VESC to 45A, the motor power will be 10cells x 3.7V/cell x 45A = 1665W or 70% of the motor's max power (2400W).

Keep in mind that when the cells are fully charged, wattage is higher, and when they're closer to discharged, it's lower.