Charging issues

Hi. I recently changed my alternator on my 97 police engine. Most of those take a 175 amp alt, but I was told because I didn't have all the extra stuff that police use, I didn't need one that big. I bought the 135 amp. Now I'm having issues with my battery charging, and it's a brand new battery. I had a test done, and the alternator is reading 13.8, but I'm still having issues. Could it be that I do need the 175? I've checked the connections and they all seem to be good. Please help?

13.8 at idle? What's the charging rate with all accessories on? And rate with rpms reved?
Did the place that sold you the alternator just not have a the 175 and wanted to sell an alternator?

http://www.aa1car.com/library/charging_checks.htm

If your electrical system is running 13.8v when the engine is on, then your system is charging. Check your battery.

The CVPI used the 135 amp alternator up through 2003, then switched to 190/200 amp clutched pulley Mitsubishi alternators. While the 175 was an available upgrade for your year, the 135 should be sufficient.