How long of a rest? After being charged, 6s can read over 13v for a day or so and 12.8 for a long time before the surface charge wears off. You might stick an hydrometer in there after the rest period and get a comparison with the voltage reading for estimating SOC.
That hydrometer reading can be a shocker if you haven't done that before. which is where you go out and try to find a charger that can do over 15v :( Hint--VEC1093DBD. See:
http://www.wholesalesolar.com/pdf.folder/battery-folder/charging_instruction_2011_2.pdf