Before coming to any conclusions, I would do some checking of a couple of areas... first make sure all connections from the alternator to the battery are clean and tight...

Then check your alternator output voltage with a known accuracy meter.. The stardard output range quoted per (at least one) Toyota manual was an alternator output voltage range of 13.9 - 15.1V with a fully charged battery (battery charging at 10A or less). This was measured at the "B" output terminal on the alternator..

If it's trully putting out 16 - 17volts, you do have an alternator regulation problem...

I have had a few weird batteries that would boil and spew acid vapor even with a good alternator..