balancer ...

why when charging li polymer in mutli cells needs a balancer While charging of lions didnt?

so if i would to charge multii lions in series, do i need a balancer charger too ?

yes, you would need a balancer.

Yes if LiPo or Li-Ion are in a pack, they should be balanced...at least periodically.

Part of why this may not seem as prominent with Li-Ion's is in part because most chargers are single or double cell (i.e. Pila IBC, Ultrafire, DSD), and mostly with individual protection circuits built into the bottom of the cells (with AW & Pila brands, at least).

However, any commercial Li-Ion pack (i.e. Laptop) has protection & balancing circuits built into them. Many custom made Li-Ion packs do have balancing wire leads in addition to main Red/Black charging leads.