Twist wrote: ↑Thu Jan 21, 2021 4:16 pm
What are the advantages of the Nuc controller if on the OEM battery?
1) Throttle response. The Nuc has programmabe endpoints AND has an 8-pt throttle curve. So you can set the response too be as quick/slow as you like. The stock controller and throttle is very non-linear. Coming from a gas bike you may be disappointed how much twist it takes to get the bike to 'leap'. Sapping the front wheel up takes a bit of learning the timing. Now it just takes a quick snap of the wrist like any gas bike.
2) Torque. I think the stock controller is limited to ~100(150?)A per phase into the motor. The Nuc does 400A+. So it has a ****LOT**** more torque off the line. Ok, now some ohms law / EE stuff is coming...
Power = voltage * current
When the motor is stopped / turning slow, there is no back-emf and the voltage is only the current * the motor resistance. The voltage across the phases is therefore low. So lets say its 10V. 10V*400A=4kW.
The control is very efficient. Probably mid 90s%. But lets assume 100% for now for simplicity (close enough). Power out = power in.
4kW / 60V battery = 66A. The oem battery BMS will cut you off somewhere a little over 100A. So at low speeds there is ZERO advantage to a better battery. The factory battery can deliver up to about 60V*100A = 6kW.
Its helpful to remember in the mechanical world:
power = torque * speed(rpm). (there is a fixed constant snuck in there if you don't use metric units.)
Anyway, you can see at low rpm, you can still develop a LOT of torque and not require much power.
So where does a better battery help? More power. A 72V 300A BMS limit battery from litespeed can supply up to 72V*300A = 21.6kW. So that big torque you had a low speed w/ the oem battery no longer tapers off quickly w/ increasing speed. You still have crazy torque at much higher speeds. :) Can never have enough power!
3) Modes. The Nuc controller has three FULLY programmable modes. I'm plotting to turn it way down for the kid - like his OSET. You can limit top speed, torque, throttle response, power, regen braking, etc independently in each mode. So there can be a 'kiddo' mode, 'wife' mode, and 'are you ready to die?' mode.
FWIW, You don't NEED bigger wheels, different battery, or bigger controller to have a ball of fun. They are still a hoot riding stock. Kids will never notice the difference that it doesn't respond exactly like a gas bike. My wife just knows you twist the throttle and it goes. I'm picky though and it drove me nuts. Every gas bike rider who's been on my orig could notice it had a slow throttle. I'm hooked on the Nuc controller for the throttle response alone.
