At what point John? When first started it's going to charge at a higher rate than it would after it was running for say half an hour. If it does stay up at that point there is adjustment in the voltage regulator. If you don't have a service manual for your car look up your year and model in the reference section at the top of the page for the specifications.
Good news! The weather today as good, so I took her out for a spin.. After a 25 minute ride, I turned on the high beams and the heater fan to full, then revved up the engine to 2K RPMs and it held 13V on the charging system.. I think I am all set! Have a great day..