I didn't know that could be done and that the cells are available on eBay. I have a pile of drills from over the years that the replacement batteries cost more than a new upgraded drill. Is it difficult because there are a couple I really liked?? Thanks, JIM@t-tony you can open the battery assembly, identify the cells and get new ones of ebay. Pretty simple DIY, you only need to repack cells and solder tabs of new cells in correct order. You also can upgrade to ni-mh cells, they are less prone to memory effect.