try battrygraph
use it on both my N900s just fine
nothing fancy, simply a graph & a numerical display of a couple informations (mAh, mvolts are most interesting)

i tried the scripts on both my N900s for several weeks w/out getting anything but 2100+ mAhs with standard BL-5J batteries - probably only work for the super-duper whatever batteries ¦-))))))
more likely not @ all