Shouldn't controller output voltage be proportional to motor RPMs?
The first time (which was very recent) that I saw an electric motor (Agni) list its volts per RPM, I wondered why everything seemed to be using constant voltage.
And the graphs I've seen here back up that curiosity. For a given voltage there is a maximally efficient RPM, near the maximum RPM. It should follow that for every RPM, there is a maximally efficient voltage. And not just maximum acceleration, but maximum acceleration and efficiency of power usage.
Do the Kelly BLDC controllers output a fixed voltage, or is the output voltage the same as the input voltage? I'm hoping the latter. And if so, can I just create a manual switch to switch a battery pack's serial / parallel arrangement? Please?
This seems extremely similar to shifting mechanical gears, without the friction loss. I can see it being implemented with an interface very much like a ratcheting sequential motorcycle gear box. Without the clutch.
Hmm, I guess for increased acceleration you would want more amps and less volts, also like mechanical gears? I need to look at those graphs again. No, I think you would still want the maximally efficient voltage per RPM for maximum acceleration?
Four battery packs, 36v and 200a max (36 Headway 10a cells) each, gear equivalents:
First gear: Full parallel = 36v 800a
Second gear: Parallel / serial = 72v 400a
Third gear: Full serial = 144v 200a
I think I finally grasp the difference between amps and volts. I'm sure I've read it before: Volts = speed, amps = torque. Fast (high voltage) motor with no torque (low amps) = going nowhere. Slow (low voltage) motor with lots of torque (high amps) = definitely going somewhere, but slow (and inefficient if you don't need all the torque).
I also think an emergency mechanical disconnect switch within easy reach is a good idea. Physically separate the batteries from the controller. "When all else welds shut." Frankenstein style (knife switch).