Thank you for tips.
I have updates the dvcc.py file: replaced min(ceil(max_charge_current), sc.currentlimit) → min(max_charge_current, sc.currentlimit) and modified initialization part setting 0.4 instead of 0. (0.4 A I choose after several tests, it appeared 0.3 is not enough, one out of 2 batteries was discharged every couple seconds for a short period of time.) The update noticeable changed the system behavior.
With ceil() and CurrentOffset = 1 and DVCC Max charge voltage = 51.8, the system loads battery to 51.8V and keeps it on this level.
Without ceil() and CurrentOffset = 0.4 and DVCC Max charge voltage = 51.8, the system loads battery to 51.8V and than starts gradually decrease voltage from 51.8 down to 50.7 during 7-10 hours, then it supports this voltage during approximately another 7-10 hours (the battery’s BMS changes CCL from 0 to 5..7A and back to 0 pretty frequently, every 10-15 minutes, but for really short time, like just couple seconds). Next, SOC decreases down to 99%, CCL soars up to 40A and inverter quickly loads battery up to set up limit - 51.8V. And the cycle repeats:
So, my question here is: what is better for battery long life, being loaded up to 51.8 and supported constantly on this level, being loaded up to 51.8 then gradually discharged down to 50.7 then keeping this voltage for a while and finally loading again up to 51.8, maybe something else?