Samsung SDI Co., South Korea's major battery maker, said Friday it has signed a 437.4 billion-won (US$300.5 million) deal to supply energy storage solution (ESS) batteries to U.S. energy firm NextEra Energy Inc.

This photo provided by Samsung SDI Co. shows its Samsung Battery Box (SBB).

The deal is part of a 1 trillion-won ESS supply agreement the two companies reached in July, according to Samsung SDI.

Samsung SDI said the company and NextEra Energy are finalizing the details of the large-scale contract to supply 6.3 gigawatt-hours (GWh) of ESS batteries, which will account for 11.5 percent of the total ESS capacity in the United States.

The key product in this deal is the Samsung Battery Box (SBB), an energy storage system housed in a standardized 20-foot container, the company said.

The SBB integrates batteries, safety systems and air conditioning units, allowing it to function as an ESS simply by connecting it to the power grid.