Sounds like you found the problem

In the picture below, the red arrows should be at the same voltage. It looks like you're seeing 1 to 1.5v difference. This is from too much resistance in the blue line. This causes the regulator to make the output at the alternator to be 1 to 1.5v higher, which pushes the battery voltage that much higher as well.

The solution is to either clean every connection in the blue loop (sometimes works, didn't for me), or the best solution, is to install a relay in place of the brown line to jump battery voltage directly to the regulator and alternator. The relay is turned on by the ignition switch. This bypasses all of the voltage drops.