Under the auspices of the US Department of Energy, Energy Storage Systems (ESS) Program at Sandia National Laboratories, electrical tests were performed on two valve-regulated lead-acid (VRLA) batteries to compare the effects of several design improvements, evaluate their applicability to stationary applications, and determine their service lives. One battery represented a baseline design, and the other an improved design resulting from a development project. The two nine-cell, 1050-1200 A h, C-8/8 batteries were tested over a 7-year period using primarily a 100% depth of discharge and approximately a C-8/8 discharge regime. A variety of charge profiles were investigated and characterized. Both batteries reached end-of-life after several hundred cycles. This paper will describe these results and overall life data, and comparison information will be summarized. (C) 2001 Elsevier Science B.V. All rights reserved.