Yes sorry I shouldn't have said just measuring SOC but more so measure SOC discrepancy between cells in the meat of the capacity curve.
So It's a lot easier to measure SOC discrepancy as a voltage discrepancy due to the linear and much sharper voltage drop over the cells capacity range.
There is no way in hell your going to be able to balance a lifepo4 cell in that flat section of the capacity scope measuring equipment isn't that good. Any equipment that mentions it can balance lifep04 without taking the cells down to the lower or upper knee is unrealistic.
Though as i see with my electric car even if your only cycling the cells many times from 40% soc - 80% soc the cells still remain balanced and are being actively balanced over this soc scope. As the BMS can take (measurable) voltage references between cells and act on them. By then time there was a (measurable) voltage discrepancy in a lifep04 cells in the flat voltage section of SOC they would be very large unbalance in SOC.
This link shows a graph with a few different lithium chemistry you can see the lifep04 is very different.https://e2e.ti.com/blogs_/b/fullycharged/archive/2013/09/13/giving-more-life-to-lifepo4-batteries
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.