Axion Power International, a U.S. company, is the maker of a slightly re-designed Battery that has been deployed for grid storage. If widely adopted, this kind of storage could enhance the usefulness of intermittent renewable energy such as wind or solar. It could be a valuable emergency backup for hospitals and similar facilities as well.
Car Batteries Could Give Power Storage a Jump - Bloomberg:

The battery is three to four times less expensive than its lithium and nickel-metalhydride counterparts and lasts “four to five times longer” than traditional lead-acid batteries.