With ever-evolving information technology, it is becoming increasingly important to secure reliable back-up power supplies in telecommunications networks, data-processing facilities, utilities, etc. While valve-regulated lead-acid (VRLA) batteries are predominantly used nowadays, their diagnosis technology is not fully developed. As partial-discharge techniques require temporarily shutting-down of the system and also degrade battery life, manual testers based on an ohmic techniques have become popular. Accordingly, the Battery Condition Watcher (BCW) has been developed and commercialized. This is an automatic monitoring system with remote communication capabilities. It measures the internal impedance, voltage and temperature of individual cells or batteries with high accuracy. These parameters are subjected to data processing to enable diagnosis of battery conditions and life. Some aspects of field usage of the BCW are reported. (c) 2006 Elsevier B.V. All rights reserved.