Battery protection-where do we stand?

The potential for catastrophic damage from battery failure is often unappreciated by system designers or users. Within the IEEE and other standards-making agencies, no comprehensive guidelines exist for the protection of battery circuits from such damage. The batteries considered are of the lead-acid type. Full-load current from a large uninterruptible power supply (UPS) battery may reach thousands of amperes, with fault currents 10-12 times as high. Battery destruction during a major fault can acid-contaminate an entire building, escalating damage far beyond battery cost or equipment downtime alone. Often, no protective devices at all are provided because of a fear of their nuisance operation. Of special concern is the internal fault that may go undetected by devices at a battery´s main terminals. The author outlines some user experiences, brings together existing recommendations, and hopes to stimulate development of useful standard practices