Future reference, you should never use a charger from one notebook on another notebook - especially from different makers. Current is not really the problem, it is the voltages that mater. And while +18.5V is very close to +19.5V, there is 38 volts "difference in potential between -19.5V and +18.5V. Since there is no industry standard for notebook power, power connections, or polarity of the connections.
I personally think you were lucky you did not fry a power supply, or the internal regulator/charging circuits of the notebook (or notebooks). I too recommend using OEM supplied or recommended replacements - or at least seek the advice of a knowledgeable, qualified technician first.
Huh? That makes no sense! There are no 12V rails on the 19.5VDC output of a notebook power block!