Starting at 12.75v took ~3 days for my 5A LiFePo4 charger (I measured 4.9A) to hit the shut off 14.4v threshold. This was a 12.8V 300ah battery. Did 2 of them before they go in series.
Agreed.
Label your cells (i use letters, A, B, C...), disconnect, and take notes of voltages right away, a couple hours and tomorrow. You will want this down the road... you'll see...