Substitute batteries

[freerunner at newkirk.us]

OK, I have a few Nokia batteries laying around, BL-5c and BL-6c, and
desktop chargers.  They power the Freerunner fine, and seem to charge when
they're in the FR plugged in.  But the Freerunner doesn't know what to do
with them apart from that, presumably since they lack the Openmoko coulomb
counter circuit.  

So the questions are:

Is it safe to charge one to capacity in the Freerunner?  I'm not confident
it can sense when to stop charging.

Can the battery applet be expanded to be able to provide a capacity
estimate for non-openmoko batteries?  (base it off voltage from battery?
How do most cellphones come up with their estimates?)

How complex is the coulomb-counter circuit - is it something that could be
acquired and retrofitted onto a Nokia battery with moderate modifications
of the casing?

j