Battery packs having jelly roll battery cells of different designs or capacities may have an imbalance in the charging and/or discharging current supplied to and provided by each jelly roll due to differences in capacity specific impedance between the battery cells of the battery pack. A C-rate (i.e., current relative to rated capacity) of a first and second battery cell connected in parallel may be balanced by altering properties of an active layer and/or a thickness of a current collector of the second battery cell to reduce an impedance of the second battery cell.