Cordless Rotary Hammer Drill Restoration and Battery Rebuild 7S60A | Makita HR200D

This tool is obsolete because it runs on old Nimh batteries. It was abandoned in Japan. Everything is fine except for the battery and the charger. I bought it to restore and want to know its quality. All that needs to be done is to clean the internal parts, put in new grease, and especially make a new battery with lithium that has the same power as the old one. The original battery contains 20 of Nimh batteries. The Nimh battery cell fully charged voltage is around so with 20 cells in series connection