From the Bell 47 PRSU post:

"The motor/alternator of the Belt Alternator Starter
(BAS) hybrid system is driven by a high tension belt
from the engine crankshaft. It boosts power under
acceleration, charges the battery, and restarts the
engine after AUTO STOP."

"The GM Belt Alternator Starter (BAS) requires 36 volts to run. What you
would save on starter weight, you lose on having to carry two extra
batteries. "

"That certainly is a drawback for most of us."

I would suggest that the "BAS" probably needs some type of a regulator to
charge 36V batteries. It should be possible to modify it to charge at 28V.
Also, I doubt that a rotary engine would need the same high current starting
capability as an instant start auto engine. If it became a real need to
adapt a
BAS I'd probably have a deep discussion with my local rewind shop.

Fred O.