Proterra, a US-based maker of battery-powered electric buses, has raised $24m in a series C funding round which included two new strategic electric industry investors, Edison Energy, a subsidiary of Edison International, and retail energy supplier Constellation, a subsidiary of US-based energy provider Exelon Corporation; previous investors who participated in the round included GM Ventures, the venture capital arm of General Motors, Mitsui & Co. Global Investment, the venture investment subsidiary of Japan-based trading company Mitsui & Co, Hennessey Capital,…