after a lot of frustration, i found out that one guy in my department wrote a program that (in the middle of other operations) checks the battery level of the nokia N810 devices; is written in C++ and uses dbus library that asks to hal, so i think that is also valid for N770 and N800.

after a few modifications i'm now able to check correctly the status of the battery!

in attached you can find the source code, with the hope that it will be helpful to someone.

bye bye