2005 Mitsubishi galant battery light comes on and head light power increases

What is your question?

Random times of driving the battery light illuminates and a power surge increases the headlights brightness while also having power drawn from the motor. Just replaced the alternator a month ago and have had no problems till the light came on. At first it was a flash here and there now it's more frequently. And for a longer period of time. While I drive with the head lights on it looks like im flashing the high beams. I checked the batter volts over time it increases beyond 12.6 @12 volts. How do I fix the power surge when i already check the grounds and fuses and harness. Could it be plugs and wire,the battery,distributor or ignition coil im at a loss.

What makes this problem better or worse?

Time driving for 30 plus or deaccaration.

How long has your 2005 Mitsubishi Galant had this problem?

A few weeks.