“The OEM e-bike charger and battery, unless damaged, are practically risk-free if used in specified ambient conditions”
Sounds as though NREL doesn’t agree, or they would have allowed charging with the above constraints.
It’s very possible that commercial insurance carrier nervousness is behind that. That’s been the explanation elsewhere. They have valid concerns about modified chargers and batteries like delivery services using independent contractors have been known to do in NYC and other metros. It’s hard to determine which bikes coming through the door are modified or not.