I'm reviving this old topic because I ended up getting one of these, an ANKER Astro3, to power a used DR680 I just bought.
For a test, I ran it tonight 4-channel with two stereo mics, both with phantom power, and I got just under six hours on 12V. (I had removed the AA's.)
mic #1 AT BP4025 - 11-52V DC, 7 mA typical (both channels total)
mic#2 AT 4050ST - 48V DC, 6.4 mA typical (both channels total)