I went through 2 batteries before finding that the red top Altima was the only one happy about trying to hold a charge around 15 volts. The gxp altnaters are known to overcharge (which isn't a bad thing) as long as the battery cells will tolerate it.

some makes/models charging above 13.5 is considered to be a problem. Welcome to gxp world where everything plays by gxp laws of physics