Go for the NiMh battery (battery space or other) instead of the NiCad (rat shack). They're the same size and roughly the same weight but the NiMh lasts twice as long. You never know...like the other night when I had a 2 show conflict...and fortunately the 1st one ended before the 2nd one started. Off I went with lotsa battery left!
p.s. when you're doing the math you don't get all the capacity. And when I measured current consumption on the UA-5, I never measured over 400mA even with phantom on.
Conditions Battery (mA) AC (mA)
phantom off 260 280
phantom on, no mics attached 290 320
phantom on, Rode NT-4 attached 360 390
and add 20mA for headphone monitoring if you use it.