IME, doesn't matter what mics you run with it, the brick will power for greater than 10 hours, no doubt. You will have no problem, assuming good/decent batteries, with 5 times what you want to record at full charge.
I have no idea on the voltage adapters. Just go with a full charge and I can't imagine you would be disappointed by dead batteries.
Per Doug, 2-3 hours charge per hour of runtime should be sufficient to fully charge the m148 batteries, and of course, do not leave it on the charger after batteries should be full.
Have fun!