LiPo for Craftsman battery

I got a battery powered craftsman drilling machine from someone, the battery did not hold charge at all.
I have a few LiPo batteries left over from drones I don't use anymore, and I thought to put those to use.
I opened the 12V craftsman battery, and removed the battery cells inside, and wired a XT60 connector where I can plug one of 4 cell LiPo battery (it should be a 3 cell for 12V equivalent, but don't have a 3 cell one)
I used a 4 cell, 4000 mAh battery, but the casing is big, so you can