I'm taking a stab in the dark here, but could the issue be that your alternator isn't putting out enough voltage to charge your battery? I've heard that some of the newer maintenance free batteries in particular need a higher voltage than the older alternators produce. I know this would not produce the delay in charging phenomenon you describe, but I wonder if maybe the folk at Autozone just misdiagnosed that??? Maybe?? Just a thought. . .
82 300 SD
77 450 SL (gone)