U.S. automaker General Motors (NYSE:GM) subsidiary GM Energy on Thursday launched an energy storage product called the PowerBank to rival EV giant Tesla Inc.’s (NASDAQ:TSLA) Powerwall product. What Happened: The GM Energy PowerBank is a stationary storage product that allows users the ability to store and transfer energy from the grid or solar panel system to provide power when there is an outage. It comes in two variants with 10.6 kWh and 17.7 kWh battery capacity. On combining two PowerBanks with 17.7 kWh battery capacity, customers can power an average American home for about 20 hours, the …