I was pretty close to 50% SOC when I started this, probably a hair over but not 52%. 12.21V was my starting voltage after about 1 hour with the batt switch off, not perfect but close enough for me.
Yes I started to taper right around 80% SOC. By the 150 minute mark I was at 91.8% SOC, based purely on the linear math and 15 minute sample rates by that time. The linear math shows I went to 100% SOC at 3:30 hours but I am not quite there, still charging at 18A.
Fisherguy's PD9280 dropped to the absorption stage at just over 3 hours, I am still on bulk at 3:30.