Battery Test Equipment provides meaningful data on battery health without significant expense or reduction in remaining battery capacity. Battery Test Equipment is typically designed for on-line ac impedance and dc terminal voltage measurement of secondary batteries. The instruments work by applying a test current across the battery string while on-line, then measuring the total current (ac ripple + test current) and the voltage drop of each cell. It then calculates the impedance. They also measure dc voltage and interconnection (strap) resistance to help determine the overall condition of the entire battery string's electrical path from terminal plate to terminal plate