When Joe Mastrangelo joined the fledgling Eos Energy Storage in 2018 in Western Pennsylvania’s Mon Valley, he said the plan was to build the batteries in China and ship them back to the United States. “That quickly changed to us moving all of the manufacturing back to the United States because it would be easier for us to scale up production. We ended up building a whole supply base to the point where 90% of the product made here comes from the United States,” he said.