Xtreme Power, a US-based developer of energy storage systems, has raised $16.4m in in its latest investment round and on its website said oil major BP was now one of its investors.
Its other new investors are venture capital firm Spring Ventures and US utility Dominion Power.
Xtreme Power makes energy storage and power management systems (pictured) for utilities, wind farms and manufacturing companies and in its regulatory filing said 12 investors provided its latest funding.
In July last year, Xtreme Power raised $29.5m from strategic and venture capital (VC) investors in its series C round.
Repeat VC Sail Venture Partners was joined as co-lead in the round by peer Bessemer Venture Partners and US industrial group Dow Chemical’s corporate venturing unit, although a source in the deal said BP joined with the others a year ago.
Additional new investors in that round included Posco ICT, an engineering and technology services company formed out of the merger of Poscon and Posdata in January with a specialist "department for future growth" in clean-tech; US construction group Fluor; and SkyLake Incuvest, a private equity investor in Korea.
Xtreme had raised about $20m previously, according to news provider VentureWire, and its battery – originally developed by car maker Ford – is used to store wind and solar power.