Thanks for posting this. The stator is the same diameter as the BBS02, but 66% wider. The BBS02 has been run at 30A, so that suggests that the BBSHD "might" be capable of 50A if run with an external controller. Doing that would of course, void the warranty.
Karl and Eric have run them up to 50A before experiencing occasional heat issues (external 6-FET using 3077's). Of course, anyone who tries this should add a temp sensor.
An external controller also opens up the possibility of using a 60V battery. There's no reason the motor couldn't do that, it's the stock controller that is limited to 13S / 14S (48V / 52V). However, I suspect that the drive could not survive mechanically, or at the very least would suffer very rapid wear.
Voltage requires a commitment, but max amps are easily adjusted day by day. Therefore, I'd stick with the common 48V / 52V packs, especially since the fewer cells we use in series, the easier it is to fit a pack in a small frame triangle.
To get a small 4P pack to put out peaks of 40A, you need 10A per cell. Two years ago, that was difficult to find, but now?..we have the 30Q and GA cells. A 48V X 40A pack would be about 1920W, which I believe is near the mechanical limits of this drive. Higher volts would allow lower amps (at the same power), but then the same Ah size of pack would have one additional string of cells in series, making the pack physically larger and harder to fit.
4P of the GA cell = 13.6-Ah in a tiny 4P pack. Not long-range, but...if you have room for a larger pack, you have the option of a less expensive cell in 5P-8P...