By Daniel Leussink and Miho Uranaka TOKYO (Reuters) – Panasonic’s battery business must focus on boosting productivity, Group CEO Yuki Kusumi told Reuters, signalling the Tesla supplier may hold off building a third battery plant in North America as demand for electric vehicles cools. The battery unit, Panasonic Energy, had previously said it aimed to decide on building the factory by the end of March. But Panasonic Holdings CEO Yuki Kusumi said in an interview that a decision would be made only “when the timing is right”. “I keep telling people we need to think about thoroughly raising produc…