A fire broke out at 2 a.m. in the charging area of a lead-acid battery manufacturing plant. The plant’s internal contingency alarm, associated with the smoke detector, was triggered. The security guard was able to extinguish the fire with a powder extinguisher, and the power supply to the faulty charger was shut off at 2:20 a.m. The internal contingency plan siren was disarmed at 3:08 a.m., as the sound could be heard 1 km away. After being reset at 4:29 a.m., a fault on the system caused the siren to sound again. The siren’s relay was eventually disconnected at 5:00 a.m., although many residents were inconvenienced by the alarm. Twenty or so batteries had to be replaced at a cost of €2,000.

The fire had been triggered by overheating of the connections during the charging cycle at 100 A following a 15 A discharge cycle. A short circuit caused by a gap between the cables and screws initiated the fire. This faulty tightening of the cables was explained by the use of cables of an earlier reference because the equipment requested was insufficient in quantity and customer had an urgent request. The tightening torque had not been respected, and the electric screwdriver used had not been checked. The round performed by the security guard, conducted every two hours, was not enough to identify the incident at hand.

The operator undertook the following operations to prevent this type of accident from reoccurring:

• sorting of cables and checking of current stocks when reference changes occur;
• parameterisation of electric screwdrivers according to the commercial recommendations and inspection every 3 months to improve cable tightening;
• preventive maintenance on all charger cables;
• study of the possible installation of a video surveillance camera in the charging area with the relay of images to the site’s guard station.