Lithium batteries on boats: it's rarely the boat's system that starts the fire

If you own a boat, the lithium battery most likely to cause a fire probably isn't the one running your fridge. Marine electricians and safety authorities keep finding the same thing: it's the drill, the drone, the handheld vacuum and the phone left charging in the cabin.

Australia's maritime regulator has documented how serious this can get. The Australian Maritime Safety Authority investigated an explosion aboard a berthed charter fishing vessel that was destroyed when a lithium-ion battery, connected to a charger in a way that bypassed its battery-management safety system and installed in an unventilated space, went into thermal runaway (Australian Maritime Safety Authority [AMSA], 2024). The blast scattered debris up to 30 metres and ejected a 200 kg deck winch. The vessel was beyond repair.

The pattern behind marine battery fires

Properly installed, marine-grade lithium (LFP) house systems have a strong safety record. The recurring problem is portable gear: tools, toys and devices that were never designed for a hot, salty marine environment, left on charge unattended for long periods. When one of those cells fails it still enters thermal runaway, releasing intense heat and toxic gas (Larsson et al., 2017), just in the confined space of a cabin. Marine safety experts are consistent on the fix: these items are far better stored cool and dry onshore than charging aboard.

Safer charging and storage onboard

• Install to standard. Have fixed lithium systems installed to the Australian Standard by a competent marine electrician, and never modify a charger in a way that bypasses the battery-management system (AMSA, 2024).
• Ventilate. Make sure battery installations are ventilated as the standards require.
• Charge before you go. Charge portable devices ahead of time, not unattended aboard for hours. "Charge it before you use it" is the marine expert's rule of thumb (Nautilus Marine Insurance, 2024).
• Store portables onshore. Keep spare tools, toys and portable batteries cool, dry and ideally off the boat, or in a fire-resistant containment bag if kept aboard.
• Fit detection. Smoke detection on a vessel, alongside gas and carbon-monoxide alarms, gives you early warning.
• Watch while charging. Heat, swelling or an odd smell means disconnect the charger if it's safe to do so.

On the water, help and escape routes are limited, which is exactly why prevention matters more at sea than almost anywhere. A few habits, professional installation, no unattended charging, and portable gear stored onshore, remove most of the risk. If you want the full picture, our online Boats course covers safe lithium-ion practice for vessels from start to finish.