I have the same problem. The battery life is terrible. 6-8 hours max. This needs a much larger battery. How about an extended battery kit? Larger capacity, a larger one with a different back to accommodate the thicker battery.
11/12 Update: I took it out today for the first time and had it in a profile that D-Star/DMR and max power set. I would be out for about 3 hours and had one QSO about 5 minutes long. When I returned home, the SO4 was beeping with a low battery warning. I plugged in the power adapter. With the power adapter plugged in it shows 54% unplugged, about 12%. Is this normal? If it is, that is fine. This unit is just a few days old, and if there is a problem, I want to make sure and address it.