Vanadium redox flow batteries show enormous scope in large-scale storage and load balancing of energy from intermittent renewable energy sources. Although a number of studies have been published in the last two decades on various aspects of these flow batteries, very few have reported on practical aspects such as design considerations, guidelines and operational failures. Adequate attention to engineering aspects, failure detection and diagnosis are essential for smooth operation of the flow batteries. This paper discusses a few case studies of operational failures during the design and development of kilowatt-scale flow batteries together with their diagnoses and remedial actions. Specifically, failures in the membrane, tubing network and state of electrode have been discussed and suitable recommendations and guidelines are given to avoid these. In each case, rectification of the malfunction was confirmed through results obtained using electrochemical testing protocols established in previous studies. Based on these experiences, good practice guidelines have been recommended for proper fabrication, assembly and characterization of stacks. © 2020 Elsevier Ltd