Watertown battery maker A123 Systems hit with countersuit

Four months after launching a pre-emptive lawsuit, A123 Systems Inc., a Watertown maker of rechargeable batteries, was hit late Monday with a federal patent-infringement countersuit by a University of Texas professor and Canadian utility Hydro-Quebec.

The Texas scientist, John Goodenough, and Hydro-Quebec also sued Black & Decker Corp., which makes DeWalt brand 36-volt power tools that use the A123 batteries. He's seeking unspecified damages.

Goodenough claims in a suit filed in US District Court in Dallas the A123 batteries violate two patents he holds on use of a chemical compound, lithium iron phosphate, as a component of rechargeable batteries.

Hydro-Quebec bought a license to the patents in 1997. But in April, privately-held A123 sued Hydro-Quebec in federal court in Boston after the utility began threatening a lawsuit, asking a judge to declare the patents aren't valid and aren't being infringed anyway.

(By Peter J. Howe, Globe staff)