SEOUL, Nov 4 (Reuters) - The battery unit of South Korea"s SK Innovation Co Ltd (096770.KS) plans to invest $2.53 billion to build a new electric vehicle (EV) battery factory in China, China"s local government backed Yancheng News reported on Thursday. SK Innovation"s wholly-owned battery subsidiary SK On, which supplies electric car batteries to Ford Motor Co (F.N), Volkswagen (VOWG_p.DE) and Hyundai Motor Co (005380.KS) among others, has battery production sites in the United States, Hungary, China and South Korea.The company had said in September it planned to build a new battery factory in China with an initial investment of 1.2 trillion won ($1.01 billion). "SK On has been building (battery) factories in the United States, China and Hungary as a growth strategy after securing battery orders in the global market," SK On said in a statement.SK On said last week that it has an order backlog of about 1.6 terawatt hours (TWh) of batteries worth about 220 trillion won, which could power about 23 million electric vehicles. ($1 = 1,183.4000 won)