A123 Systems, the bankrupt lithium-ion battery maker bought by Chinese automotive manufacturing giant Wanxiang last year, has mostly been associated with electric vehicles. But a quarter of the company’s revenues last year came from the megawatt-sized grid energy storage systems it’s installed with partners like AES and utilities across the world.

Monday brings news that Wanxiang intends to keep that grid battery business alive, in the form of A123 Energy Solutions. The business unit will build both ALM 12V7 batteries for replacing lead-acid industrial backup power systems, as well as its megawatt-scale Grid Storage Solution containerized battery systems, which have already been deployed in excess of 100 megawatts in grid projects from Hawaii to Chile, as well as back in Massachusetts.

The grid division will be based in Westborough, Mass., with offices in St. Louis, Mo. and Suzhou, China, according to Monday’s release, which didn’t specify just how much money was being invested in the new endeavor. Attendees will be able to check out A123’s booth at the American Wind Energy Association’s Windpower 2013 conference this week in Chicago.

Nor did A123’s announcement say if the company had any new grid storage projects in the pipeline. To date, A123 has installed just over 100 megawatts of energy storage projects with partner AES Energy Storage, which made up 24 percent of A123’s 2012 revenues, and has significant projects with utilities including Maui Electric, Southern California Edison, Sempra Energy and NSTAR.

Earlier this year, AES decided to pick Mitsubishi/Yuasa over A123 for its latest, 20-megawatt lithium-ion energy storage project in Chile. Of course, that decision was being made in 2012, when A123 was still in the midst of its bankruptcy. Monday’s new brand launch is obviously meant to overcome any impression in the industry that A123’s grid storage business has been left by the wayside in its transition to Wanxiang’s ownership.

A123 competes against other lithium-ion battery makers such as Altairnano, Mitsubishi/Yuasa, Samsung SDI, Johnson Controls and Saft in the grid storage business. Lithium-ion batteries are still expensive for most grid storage applications, compared to existing grid-scale batteries like the super-hot sodium sulfur batteries from Japan’s NGK -- a chemistry that is also the focus of General Electric’s sodium-metal Durathon batteries. More advanced battery chemistries, such as metal-air, offer long-term promise of much-reduced costs, but have years to go in testing and R&D.

Building batteries is a capital-intensive business, and covering the 20-year warranties that utilities need for mass deployment is a challenge for startups without deep-pocketed project partners. Xtreme Power, which has installed 77 megawatts of its advanced lead-acid batteries for grid balancing, recently announced it’s selling its factory to concentrate on battery management software and services, in hopes of speeding profitability and avoiding production costs.