Confidential Human Factors
Incident Reporting Programme
The Charity
Aviation
Maritime
M2301
Initial Report
During a shift of anchorage positions, the vessel experienced an incident in the lower engine room when the power management system (PMS) initiated the startup of a third generator. This action was necessitated by the increased load on the switchboard and the use of the bow thruster. Shortly after the generator was brought online, a loud, short-duration bang was heard and felt throughout the lower engine room. Following this noise, the generator’s battery alarm was triggered, prompting immediate concern. The engine room crew quickly reported the situation to the bridge, and as a precaution, the yacht was anchored as safely and swiftly as possible.
Upon investigation, the crew detected acrid-smelling smoke and discovered that two generator starter batteries had exploded in the engine room and were severely damaged. The force of the explosion shattered the battery’s fibreglass covers and damaged the floor plates.
A build-up of hydrogen gas, a by-product of the chemical reactions that occur when charging the batteries, was assessed as the cause of the explosion. A spark from nearby electrical equipment possibly ignited it.
A more thorough investigation revealed that the batteries were not of sufficient capacity for their intended use, which significantly increased the risk of uncontrolled failure. The previous chief engineer was aware of this issue but failed to communicate it to the incoming chief engineer during the handover process.
CHIRP Comment
Although recent focus has been on issues surrounding Lithium-Ion batteries, many other battery types remain common across the industry. This incident underscores two critical areas of concern: battery management and operational handovers.
Regular maintenance and inspection of battery systems are critical, especially regarding capacity, condition, and proper ventilation. Insufficient ventilation can lead to danger. Batteries smaller than the recommended size or lower in ampere-hour (Ah) capacity can explode when used or charged.
The outgoing engineering team demonstrated poor engineering standards in continuing to knowingly use under-capacity batteries, which should have been replaced at the earliest opportunity. At the very least, the design deficiency should have been documented, reported to management, and mentioned during the handover to a new engineering team.
Key Issues relating to this report
Alerting- The off-going engineer did not arrange for the batteries to be replaced immediately despite knowing they were unsuitable.
Overconfidence—Even though the team knew the risks of using the incorrect equipment, they continued using it. This inaction could have cost someone their life and threatened the vessel’s safety.
Communications—It is unlikely that the chief engineer was the only person who knew about the underrated batteries. Critical equipment items must be discussed so that risks can be communicated, safety concerns can be identified, and action can be prioritised.
CHIRP has received several incident reports concerning battery maintenance and use and wants to provide some key safety tips.
| 1. Make sure the batteries are correctly rated for the installation |
| 2. Check for deformation, corroded terminals and blocked vents |
| 3. Ensure that the electrolyte, where appropriate, is maintained at the correct level |
| 4. Battery storage boxes are to be well-ventilated and capable of regular physical inspection. |
| 5. Battery load tests to be carried out regularly |
| 6. Voltage monitoring to ensure that overcharging is not occurring. |
| Remember- Correct rating, preventing overcharging, and safe ventilation of hydrogen fumes are key to preventing an explosion. |