Batteries and AC phenomena in UPS systems: the battery point of view

The characteristics of the lead-acid battery are considered in terms of electrochemical efficiencies, overvoltage, and resistive impedance. Electrochemical efficiencies and resistive impedance are considered in terms of both the discharge reaction and the recharge reaction of a battery. These characteristics are used to explain the reaction of the batteries to certain AC phenomena. Definitions for AC phenomena are given in terms of DC ripple and high-frequency shallow cycling (HFSC). The relationship between battery characteristics and DC ripple is discussed in simple battery rectifier systems and battery rectifier systems incorporating a resistive load. The possible adverse effects of DC ripple are identified. In addition, HFSC is considered in terms of battery characteristics, and a battery rectifier with an inverter is taken as an example. The consequences of this condition are identified in terms of capacity walkdown, leading to short service lives. Finally, battery design and its operation are also reviewed in respect of the ability of designs to withstand the AC phenomena identified in the present work. Some observations are also given on early attempts to attribute limits to the ripple condition, and suggestions are made for its detection.<>