The new era of big batteries has already drawn scrutiny after fiery electric-car crashes across America and Europe. Now, U.S. city planners are worried about the same risk of hard-to-control blazes as these power-storage units make their way into basements and onto rooftops. “You can have these things go on fire, and then hours or days later, they can reignite,” presenting a new challenge for first responders, said Paul Rogers, who led New York City’s effort to establish battery safety standards until he retired as a lieutenant with the fire department earlier this year. Firefighters — “if they act inappropriately — they could get killed,” he said. Improvements in energy storage are revolutionizing how and when electricity is used. Batteries now fuel everything from handheld devices such as smartphones to the electric cars proliferating around the world. In the latest trend, racks of batteries stacked […]