An eyeopener indeed. To explain why is was a bit surprised that there is actually a single battery option (although knowing nearly everything on a 737 is optional it shouldn't really be surprising), our generic transition training CBT provided by boeing when transitioning from classics to NGs told us "all Boeing 737 NGs are equipped with dual batteries" which seems to be some misinformation. Not really surprising as the boeing CBTs are not all that good anyway, but still...