Auto-charge 8.2V Lithum-ion battery pack
Please provide FAR MORE detail.
Do you have a specific battery in mind?
What is your application?

If 8.2= 8.2V it implies 2 x 4.15V cells = (probably) two x Lithium Ion (LiIon) cells in series. If so, use of a LiIon charger or a LiIon charger IC is required.

2 x LiIon in series should never be exposed to more than 8.4V but 8.2V is safer.
BUT there can be quite a lot more than that to LiIon charging.
 Please provide details -  What mAh, cell type, use, ...?