Electric car and battery maker Tesla invested $1.5 billion the cryptocurrency bitcoin, according to a filing made public Monday. Tesla said in a Securities and Exchange document that it changed its investment policy last month to provide more flexibility in terms of diversification and maximizing returns on funds not required to maintain operating liquidity. “As part of the policy, which was duly approved by the Audit Committee of our Board of Directors, we may invest a portion of such cash in certain alternative reserve assets including digital assets, gold bullion, gold exchange-traded funds and other assets as specified in the future,” the company said. “Thereafter, we invested an aggregate $1.50 billion in bitcoin under this policy and may acquire and hold digital assets from time to time or long-term. Moreover, we expect to begin accepting bitcoin as a form of payment for our products in the near future, subject to …