Hi Mitch,

sorry for the question, but you need a PIC to charge a lead acid battery?
There are a lot of charging circuits out on the web.
Look at national.com for the datasheet of the LM317, there is also an application circuit as lead acid charger.

Back to your question...
when charged, the battery is full when the terminal voltage is around 14.4V, depending on temperature and charge method.
With 12.6V you will not get your battery fully charged.

Regards,
Ingo