When hot shoe flash just doesn't have enough oomph, photographers go to studio strobes.  The challenge with strobes has always been availability of power.  Most major strobe vendors have developed high output battery pack systems so AC is not always required, but these packs have been in most cases heavy and expensive.  Profoto released the self-contained B1 series a while back and they have been very successful.  Now available is the B2 system which uses an external generator pushing 250ws.  It's pricey so let's have a look.