A majority of the 1,000 auto workers at the car battery park Blue Oval in Glendale, Kentucky, have signed union cards to join the United Auto Workers. The battery park, a joint venture between Ford and South Korea’s SK On, is expected to ramp up hiring to 5,000 hourly workers by 2030. It has twin battery plants. But the second one is on hold due to low demand for electric vehicles. At the first plant, workers are testing battery module packs from facilities in Georgia, as the plant prepares to become fully operational next year.