By Rob Daniel Tesla, the Austin electric-vehicle powerhouse, reportedly soon will have fresh supplies of batteries for its popular models. Tesla, (TSLA) – Get Tesla Inc. Report the Austin EV powerhouse, soon will have fresh supplies of batteries for its popular vehicle lines. BYD, (BYDDY) a China-based company that makes its own electric vehicles and is backed by billionaire investor Warren Buffett, said it shortly would be supplying Elon Musk’s clean-energy carmaker with perhaps its most important component. “We are good friends with [Tesla Chief Executive] Elon Musk and we are preparing to s…