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Taking care of lithium batteries to avoid fire on board a yacht

25 July 2023

Following a number of reported lithium battery fires in the past several months, yacht crew have been asking for a more in-depth look at how to minimise the risks, and what to do should you experience a fire. With so much technology running on lithium batteries, now more than ever, yacht owners and crew need to understand the best practices.

We want to thank Adrian Coetsee, PYA Board Director for Engineering Training, for sharing with us these unique insights on how to properly handle lithium batteries onboard and some of the things to look into for safer use and storage.

A guide to lithium batteries

With the advances in lithium batteries we are now finding them in more and more interesting applications, but this new flexibility brings its own challenges. One of these new risks is fire, the MCA has noted this and released MGN 681 to give some guidance on best practices on how to store, charge and maintain these new systems.


Where we once used petrol engines, we now have batteries, from large tenders to smaller water toys like Dive bobs or efoil boards down to the batteries in your phone or laptop; they all use the same chemistry and all have the same increased risk of fire.

This MGN is specifically aimed at batteries over 100Wh, but not forgetting smaller batteries from laptops and phones, which are less risky due to their size but still have increased risk of fire.

For reference, a large drill battery would be around the 100Wh lower limit, if being stored ideally in a battery/fire box (if being charged or in a vehicle then in a REG yacht space A space.) Around page 97 (depending on version) Chapter 14 fire safety is where you can look.


Stages of a Lithium battery fire

Let us explore some of the stages of a lithium battery fire and why this occurs:

Overheating leading to thermal runaway.

Stored batteries shouldn’t be kept in an area that is above 45C. While charging batteries get warmer, the potential for thermal runaway starts between 60-70C. In best practice, linking these temperature alarms to the ship's monitoring system is essential. If caught early enough this can be stopped by halting charging or if in use, then preventing the battery from discharging.

Once they’ve reached this temperature these cells shouldn’t be used or charged again as the thermal runway will continue and these batteries need to be disembarked - either repaired or replaced by their manufacturers.


Off gassing

Let’s take a closer look at what’s physically happening in the battery: 

Battery packs that have a way of venting instead of exploding and fire are of lower risk. Off gassing is a sudden release of carbon dioxide, carbon monoxide, and other volatile organic compounds - these gasses are difficult to predict and could gather at head height or deck level, complicating matters.

These gasses also contain hydrogen cyanide, soot, oxides, lithium, cobalt amongst others these vapor clouds are hazardous and potentially explosive.If off gassing doesn’t occur this might be shown as a deformed or bulging battery pack.

Hissing and popping and then fire

Some of the warning signs:

A damaged battery at this stage will need appropriate fire fighting measures. The “smoke” released will have a sweet chemical smell which is made up of nanoparticles of heavy metals. The temperature will have risen and the heat load in the battery pack is now substantial. 

Water dousing will eventually stop the fire and after that reduce the runaway temperature rise. This will take a surprisingly long time, all the time emitting gas and smoke and causing heat damage.


Best practice to extinguish.

How to extinguish a battery fire and taking steps to protect electrical supplies:

For smaller fires a dedicated fire extinguisher could work if caught early enough but water dousing larger fires is the most effective. The residual temperature from the exothermic reactions is considerable and once thermal runaway - it won’t abate spontaneously.

The area would need to be vented as the off gasses are noxious and dangerous. If in a garage, water mist is very effective at reducing the heat load released from the thermal runaway of the pack. Remote isolation of the electrical supply is paramount too. The bilge pumping arrangement should be overspecc’ed sufficiently to remove the continued water needed. Remote or manual opening of the garage to vent should be considered too.

Storage and charging

If the yacht is under construction following the full MGN this would be considerably easier but nonetheless existing ships should try as far as is practicable.


Storage of smaller batteries should be in a dedicated box meeting international standards but not limited to EN14470, EN 16121, EN16122 and this be kept in a REG yacht PART A space.


On yachts over 500Gt all batteries over 100Wh should be stored and charged in a REG yacht part:

  • “Ideally” an A60 garage as far as practical from petrol tenders, charging outdoors is an option too.

  • NOT forward of the collision bulkhead, NOT in a technical space like engine rooms and back backed onto or in a switchboard rooms.

  • Vented directly overboard with intrinsically safe fans and sensors linked to the ship’s monitoring and fire systems.

  • The chargers should be powered from outside the area.

  • Ideally the area, switches, light and extraction should be intrinsically safe.

  • Storage area should be more than 45 deg.

  • Manual ways of opening or venting the area, that are outside the area e.g. a remote shell door opening if kept in a garage.


Battery plan

Identification of batteries onboard

Batteries larger than 100wh should have certificates of compliance and their own dedicated chargers, where possible similar systems should be used to help prevent the accidental use of the wrong chargers.

If a large selection of smaller batteries is kept in one area these should be noted e.g. If a charge station for many UHF batteries is kept in the radio room, if laptops, phones, and battery banks are kept in the bridge.

Locations of those batteries

  • Locations of the larger batteries over 100wh could be noted and shown on a GA.

  • Extractions could be shown too.

Training and maintenance

  • All crew should be made aware of the basics of battery maintenance and care and the steps to be taken e.g. If a battery is found to be overheating or worse if one is on fire.

  • The batteries and their respective chargers should be kept in top condition, any defaults noted, if some are seen to be damaged, how to remove or who to call.

Plans in case of emergencies (SOP)

Examples of things that could be included.

  • Manual release of misting or water deluge.

  • “How to” Bilge pumping arrangements for the specific zone.

  • Consider manual operation of garage doors to vent the off gassing.

  • Remote access to electrical isolation. 

The full MCA Guidance Note can be found here.

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