I bought a eighteen volt DeWalt toot set that came with a skillsaw, sawsall, and drill twenty years ago. The batteries lasted fifteen years. I bought two Replacement eighteen volt DeWalt batteries that must have been new old stock they only lasted six months. The tools were still good so when DeWalt started selling a 20 volt adapter kit I bought one. The adapter worked good but was hard it was hard to take out of the tools. The 2.0AH batteries that came with the kit were too small for the skillsaw and sawsall the run time was terrible. The DeWalt 6.0AH batteries were expensive. My son in law is a mechanic he switched from air tools to Milwaukee battery tools five years ago. He keeps a extra set of Milwaukee tools at home and he has been using Amazon batteries in them and they have been working out great. So I bought two Amazon adapters for seventeen dollars each (that come in and out the tools easily) and two 6.0AH batteries for sixty five dollars. I am very happy with the Amazon batteries and adapters they saved an old set of tools.