I've given a lot of thought to the motor I'll ultimately use. Right now I really like the BMC-V3motor, but it's a bit pricey and there's been a lot of negative discussion about how to drive it. Don't get me wrong, this motor is AMAZING! The problem is there isn't a motor controller out there at the moment that can drive it well*. This is because the motor impedance is only 0.3 Ohms, which means we're essentially shorting out the positive to the negative.
Many people who've setup this system at higher voltages are immediately turning their leads into glorified heaters when they accelerate. If you look at the above results, a 36 volt system will spin the wheel at 451rpm pulling 229 watts. If we up the voltage to 48, we still get 451rpm, but now this takes 1094 watts! That's a factor of almost 5 times more energy for the same results!
Question: Where is this extra energy going?
Answer: look at the Celsius rise per minute on the 48 volt system: 70.9 degrees C!!!! 8 gauge wires are literally meting off these higher voltage systems. The power is being converted directly into heat. This is causing motor controllers of all kinds to trip their internal breakers. You can't touch the controllers at higher voltages.
So what do we do? We need to design a motor controller that can drive really high currents. To do this, we're going to need to drop the voltage down and brute force the motor with current. For this reason, I'm going to reconfigure my formerly 84 volt system to 56 volts nominal. This means I'm changing my configuration to: (2S)((8S)(10P)). This means I'll need only 20 cells, which is what I'll have once the new pack gets here (as mentioned previously, one of them was DOA).
