A battery that was left on a charger over a given weekend was used to start a gasoline power generator. This battery was connected in series with another battery and the connection on the negative post was hand tightened. When an attempt was made to start the generator, the battery exploded on approximately the fifth click of the starter solenoid. No damage was done to any equipment or facilities and no one was injured.

The most probable cause of the accident was the severe overcharging of the battery (64 hours at 20 amp/hour). This charging created hydrogen, which combined with air or oxygen and an ignition source to form the explosion. One source of ignition could have been the loosely attached connection to the battery terminal. Another possible source may have been an internal short at the battery plates, distorted by the severe overcharge condition.

Incident Date
Jul 26, 1993
  • Electrical Equipment
  • Batteries and Related Equipment
  • Batteries
Damage and Injuries
Probable Cause
Contributing Factors
When Incident Discovered
Lessons Learned

Batteries stored on a charger can explode during use if overcharged.


Use automatic current limiting or timed circuit chargers when charging batteries.
Operators should be aware of safe practices and proper battery charging instructions.