Battery Maintenance Safety
Summary of Incident Occurring at UW-Platteville
At approximately 6:30 AM Friday, November 7, 2004 as summarized by Ernest Stracener, Director of Safety and Risk Management:
The employee had been working alone, performing routine starting and testing of emergency generators on campus when he flipped the switch on a unit and one of the two connected 12-volt lead-acid starter batteries exploded, sending plastic shrapnel and battery acid flying through the air. The air in the room was nearly instantly filled with a choking acid mist from the explosion. The employee later described the sound of the explosion: "it was as if somebody had fired a 10 gauge shotgun right next to me while standing inside a small closet". At the time of the explosion, he was standing approximately 5 feet from the set of batteries.
He was not injured by any flying debris, but did get splattered on the face and hands with acid droplets. At the time he flipped the starter switch, he had just donned a pair of prescription safety lens glasses, (but without sideshields) in order to make an entry in the logbook. The employee exited the room, radioed to alert others to the incident and promptly washed his exposed skin and changed clothes. Other than a possibly ruined uniform, temporary tinnitus in one ear and some very minor skin irritation from the acid droplets, the employee was essentially unscathed. No medical attention was required and the employee worked for the remainder of the day. The employee has been directed to complete an incident report to document the incident.
The acid spill was neutralized and cleaned up after waiting awhile to let the air clear. The splintered remains of the battery were placed in a container and removed for disposal.
An analysis of the incident leads me to believe that the cause of the explosion was due to a buildup of hydrogen gas within a battery cell -- perhaps from a cell's electrolyte level dropping to low levels. The generator starter batteries are standard 12-volt automotive lead-acid batteries. To keep them ready for emergency use, the batteries are on a 1-amp constant-current charger... I believe this "dumb" charger eventually cooked off enough of the fluid to allow a decent accumulation of gas to develop. An arc, perhaps from a loose terminal connection or perhaps internally due to the massive current draw created by the starter, was all that was needed to ignite the gas buildup.
So, that's the summary and the current working theory of the cause of the accident. We got lucky.
Here's what we're doing to head off future occurrences of the same type at UWM:
- Standard lead-acid batteries on emergency generators will eventually be replaced on a change-out schedule with gel-cell batteries.
- 1-amp "dumb" chargers will eventually be replaced on a change-out schedule with "smart" chargers that reduce the charging current as the battery charge fills to completion.
- Until batteries are changed out, battery electrolyte levels are to be visually checked on a regularly scheduled interval.
- Safety glasses with sideshields are required by campus policy for work that may pose eye hazards -- a renewed emphasis will be placed on this issue. Over the past summer, a change to the campus prescription safety glasses policy was made to require that all new glasses have permanent, brad-affixed sideshields. Additionally, every Physical Plant employee was provided with two pairs of nonprescription safety glasses of the style of their choice.
- Eyewash bottles for immediate emergency use will be purchased and mounted in each emergency generator room to provide some minimal flushing capability in the period between a splash and getting the person to a plumbed eyewash. [Our mechanical rooms with chillers & water treatment chemicals are being equipped with eyewash/drench hose units. Floor scrubber battery charging will also be moved to these mechanical rooms to consolidate operations requiring eyewashes.]