*Article* **Valve Regulated Lead Acid Battery Evaluation under Peak Shaving and Frequency Regulation Duty Cycles**

**Nimat Shamim, Vilayanur V. Viswanathan \*, Edwin C. Thomsen, Guosheng Li, David M. Reed and Vincent L. Sprenkle**

> Battery Materials & System Group, Pacific Northwest National Laboratory, Richland, WA 99352, USA; nimat.shamim@pnnl.gov (N.S.); edwin.thomsen@pnnl.gov (E.C.T.); guosheng.li@pnnl.gov (G.L.); david.reed@pnnl.gov (D.M.R.); vincent.sprenkle@pnnl.gov (V.L.S.)

**\*** Correspondence: vilayanur.viswanathan@pnnl.gov; Tel.: +1-509-372-4745

**Abstract:** This work highlights the performance metrics and the fundamental degradation mechanisms of lead-acid battery technology and maps these mechanisms to generic duty cycles for peak shaving and frequency regulation grid services. Four valve regulated lead acid batteries have been tested for two peak shaving cycles at different discharge rates and two frequency regulation duty cycles at different SOC ranges. Reference performance and pulse resistance tests are done periodically to evaluate battery degradation over time. The results of the studies are expected to provide a valuable understanding of lead acid battery technology suitability for grid energy storage applications.

**Keywords:** valve regulated lead acid battery; grid energy storage; battery degradation; peak shaving; frequency regulation
