Yes, to be both safe and perform optimally,every Li-ion battery requires adequate protection against extreme voltages (OVP/UVP), current (OCP), and temperatures, no matter the pack topology. Ifyou build a Li-ionpack withmultiple batteries in series then balancing isessential forboth safetyand health (a seriespack degrades much more quickly without balancing)
Note: you mean "series" not "parallel" in your title.