Re: Problem with new batteries keeping the charge
3-4 Hours is not enough for a full garunteed charge. You are only getting a flash charge. You'll need an overnight charge then 24 hours of sitting time to get a good state of charge reading.
Better yet - get a battery monitor like a Victron BMV 600s and hook it up. Simply using voltage readings for state of charge values is less than optimal.
Lessons learned are opportunities earned.