Utility Dive, Dec. 6, 2016, by Gavin Bade.
http://www.utilitydive.com/news/inside-construction-of-the-worlds-largest-lithium-ion-battery-storage-faci/431765/

"SDG&E's 120 MWh Escondido storage project will help mitigate a natural gas shortage in southern CaliforniaWhen completed, the larger, 120 MWh project is expected to be the single biggest lithium ion battery in service on a utility grid in the world. Both battery facilities are expected to be online by the end of January 2017 — nothing short of miraculous in an industry where deploying assets, especially newfangled technologies, can take years."