MAIB: Is your Lead-Acid battery safe?
- Safety Flash
- Published on 18 June 2025
- Generated on 18 June 2025
- IMCA SF 11/25
- 2 minute read
The UK Marine Accident Investigation Branch has published Safety Digest 1/2025, consisting of lessons from recent Marine Accident Reports. IMCA has reviewed the report and passes on to members some of the incidents which we consider to be of interest. This is one of them.
What happened?
A crew member on a barge escaped injury when a bank of four lead-acid batteries exploded on starting a generator engine after completing the start‑up checks. The four batteries simultaneously exploded as the start solenoid closed to power up the starter motor. Fortunately, the bank of batteries was housed in a secure steel battery locker that contained the explosion and limited the damage. (Figure 1). Given the wet cell nature of the batteries and the length of time they had been in service, it is most likely that the electrolyte level had gradually dropped because of continuous float charging. This exposed the top of the cell plates, which probably started to corrode. The cells shorted out when the batteries were subjected to a high discharge load, causing the explosion (Figure 2).
| Battery locker after the explosion | Destroyed batteries |
What went wrong?
Investigation found that:
- The batteries had been in service on the vessel for more than 5 years.
- The batteries were of a low maintenance, valve-regulated lead acid (VRLA) type that was incorrect for their intended purpose due to the battery circuit being maintained by a continuous float charge.
- The battery charging system was found to be working correctly, maintaining the required rate of trickle charge.
Lessons learned
- Maintenance: Batteries are a piece of machinery and require a documented service and maintenance log. The record should individually list the type of battery; where it is located on board; when it entered service; dates and details of any inspections or maintenance and, if applicable, what corrective action was taken; and when it is due for replacement.
- Hazard: Safe stowage of battery installations is crucial to contain and minimise impact in the event of a fire or explosion. To prevent a build-up of gases from the charging process batteries should be kept in a purpose-built, well-ventilated locker in a cool, dry location away from the elements. Light fittings in a battery compartment should be corrosion-resistant and flame/explosion-proof.
Related Safety Flashes
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IMCA SF 06/21
23 February 2021
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IMCA SF 19/19
12 August 2019
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