Hi Jon,
I believe that Li-Ion batteries (as opposed to NiMH or NiCad) provide a constant current throughout the discharge cycle until right near the end when they crash. So quality batteries should give you the same results if they're at least 15-20% charged, regardless of whether they're fully charged or not.
There are a few members on the boards here who sell hobbyist laser power meters. You might want to check 'em out and see how they compare to the Lasercheck. ;-)
I believe that Li-Ion batteries (as opposed to NiMH or NiCad) provide a constant current throughout the discharge cycle until right near the end when they crash. So quality batteries should give you the same results if they're at least 15-20% charged, regardless of whether they're fully charged or not.
There are a few members on the boards here who sell hobbyist laser power meters. You might want to check 'em out and see how they compare to the Lasercheck. ;-)