when building packs from reclaimed cells, any grading will lead to many cells being disgarded, so heres my proposal, fit a bms system, also a voltage moniter system, exteriour connection points to each group, so a buck stepdown charger can be used to manually balance, and use product over sum calculations to equalise the resistance of parrallel groups, so groups are not equal in number but in resistance, so some parrallel groups may have more than others, will let you know my findings.