Field experience with large Nickel Metal Hydride (NiMH) batteries in stationary applications

Nickel metal hydride batteries bring some unique values to stationary applications - high energy and power densities, cycle life, quick charge capability and safety, to name a few. Since the late 80's, small cylindrical nickel metal hydride batteries have been widely used in portable applications requiring high rate discharge and rapid recharge, for example, camera flash and power tools. Recently, large prismatic nickel metal hydride batteries have become the technology of choice in hybrid electric vehicles due to their good cycle life, wide temperature range of operation and high rate capability. Additionally, these batteries have been tested and installed in large stationary applications due to their unique values. In one of those applications, a flooded lead acid battery system, used to back up 560kW, was replaced with nickel metal hydride battery system to provide the same 15 minutes of back up time. A case study with this large nickel metal hydride battery installation will be presented in this paper.