Well, it's not Doug's fault, nor Interstate's fault that your current charging methods have been CHRONICALLY UNDERCHARGING your batteries. In fact, a good top charge and EQ probably would have solved your "bad" battery issues from the start. As stated, that 12.7-8 volts you were seeing, was, in all likelihood, surface charge, and the 12.3V was actual voltage, minus the Peukert effect.
And the fact you are now buying a new 'charge wizard' proves you are now aware of the chronic undercharging. And if you had checked SG levels, as suggested, you would have known you had a "bad" battery, and could have taken the steps necessary to bring both ocv and sg up to par. Instead you wasted how much time running back and forth, testing and replacing batteries?
In due time, you will likely be returning these batteries, as well... unless you start caring for them properly. This means charging them to true FULL, not 4 or 5 hours at float voltages. It takes several hours at 14.6++ volts to fully charge a 12v battery, followed by a good top charge, and then an EQ if necessary.
The next time you go to buy batteries, take a volt meter with you, and ask when the batteries were last charged. A good surface charge can take several days to self-dissipate. The batteries need to sit idle for a good 4 days after being charged, to get a proper RESTING OCV.
