Green Plug said today it has raised a second round of funding for its environmentally-friendly electrical power charging technology.

The San Ramon, Calif.-based company did not disclose the size of the round, which was led by Herald Investments UK, Killik & Co., and Peninsula Venture Partners. Green Plug did say that the pre-money valuation for the second round was significantly higher than the company’s first round in January, 2008.

Green Plug launched at DEMO in 2008 (see video). DEMO is produced by VentureBeat.

Green Plug will use the money to further its ambitious cause of creating smart power charging for electric-powered goods. With Green Plug adapters, you can charge your cell phone and multiple devices using a single wired connection to an electric plug. The adapters have built-in processors and are smart enough to know what is the best time of day to charge the devices so that you incur the lowest electrical costs.

The funding comes after the company recently struck a deal with Imagination Technologies Group, which owns a stake in Green Plug. Imagination will license its Meta processor for use in Green Plug’s power supply technology. Imagination will in turn offer a processor core that others can use to implement Green Plug’s technology in their various consumer electronics devices. Pure, an Internet radio division of Imagination Technologies, will use Green Plug’s technology for a smart power adapter accessory.

Green Plug’s chief executive is Frank Paniagua, who says that consumer electronics products that use Green Plug power adapters will improve their energy efficiency. Paniagua says that more than 2 billion dumb power supplies were shipped last year, wasting a lot of the planet’s resources.