Shares of Tesla Inc. rallied 2.5% in premarket trading, after a report that some German automakers have interest in buying a stake in the electric car maker. A report in "Manager Magazin" said Volkswagen was interested, as well as Daimler and BMW. The report comes after Walmart Inc. sued Tesla, alleging "gross negligence" as the retailer claimed roof fires at several stores were caused by Tesla solar panels. Tesla's stock has lost 33.6% year to date, while the S&P 500 has gained $16.7%.