Electrical/Charging system issues

I have an 88 XJ with the 4.0 and for the last little bit I've been having issues with my electrical/charging system. It completely killed my Optima red top, so I replaced it. It worked great for about 3 months then started dying. I talked to Optima they recomeneded using the yellow top instead so I got one. I did a load test and a no load test and I'm not drawing any power from the battery I'm not suppose to be.The yellow top worked great for about 6 months not it's starting to have the same problems, except it isn't completely draining the battery. I just pulled off the alternator and had it tested at 3 different places and they all said it's good. Only thing I can think of is I have a ground somewhere but I have no clue where to start. I'm really confused and frustrated.

OK. Kind of jumping in here. Make sure the battery is fully charged, then have it load tested per Optima recommendations.

If it passes, then hook it back up and use a voltmeter to measure static, engine off, voltage between the posts--looking for about 12.5 volts.

Next, start the engine and measure voltage between the posts--looking for 13.5 to 15.5 volts.

Perform a voltage drop test on the main cables AFTER you have cleaned and tightened both ends of both cables. Google "voltage drop test".

Post up what you find.