I would have expected a day enough time to remove surface charge, but 13.28 V does not sound correct ( it actually sound like the float voltage). You should apply a load to remove the surface charge; apply a 25 amp load for three minutes and wait five minutes, or...With a battery load tester, apply a 150 amp load for 10-15 seconds. ( From 12 Volt Side of Life
). We would expect healthy batteries to be sitting around 12.8 volts, but that voltage would not really indicate the capacity of the batteries. A battery that has lost 75% of its capacity could still show good a good sitting voltage.