Got a 2013 Cruze LT 2.4L. The charging system was acting up but never really had a battery light on. So I replaced the alternator. Now every time I start it up and look at the charging voltage it'll start at about 14.4 and then gradually go down. Sometimes for a while it'll stay at about 13.6 for different amounts of time but then eventually go down to 12.7 while driving. This is all with a brand new alternator and battery tested good. Any idea what causes this on and off like that? Still have never had a battery light come on and it's been doing this for awhile and I drive Uber so I go a decent distance and never had low battery starting condition, it always starts right up.