What does Marine Guidance Note MGN 681 (M) mean for yachts?

Recent guidance from the government has been published outlining the measures yacht and superyacht owners and manufacturers should take to prevent lithium-ion battery fires aboard their vessels.

Increased knowledge and understanding of the fire risks from Lithium-ion batteries in yacht crew, designers and owners will hopefully lead to better practice and increased fire safety.

Yacht fire safety risk 

Published in July, the report (which can be found here) details the growing concern over the potential for lithium-ion battery fires aboard yachts. It points out that industry groups estimate that there have been 16 total losses through fire between August 2021 and August 2022.

Whereas the International Institute of Marine Surveying published an article in February stating that there are believed to have been almost 70 fires last year involving large and super yachts.

While some of these fires would have been a result of other causes, there has been an increase in ‘small electrically powered craft’ powered by lithium-ion batteries on board large yachts which could potentially account for many of these unexplained fires.

The risk of lithium-ion battery fires has been highlighted in other ocean-based sectors too, with the US Coast Guard (USCG) issuing a stark warning to the shipping industry on the “extreme risk” of loading electric vehicles that may have damaged lithium-ion batteries onto commercial vessels.

A timely warning given the events of the Fremantle Highway cargo ship fire which was rumoured to have started “in the battery of an electric car”.

These risks are compounded by the fact that a lithium-ion battery entering, or in the midst of, thermal runaway releases various harmful gases – known as off-gassing. These gases, such as carbon dioxide, carbon monoxide, hydrogen, and volatile organic compounds, can be heavier than air and accumulate at deck level or be lighter than air and dissipate, or accumulate at deck-head level – it is not possible to predict which type will occur and these gases are flammable and hazardous.

Once the lithium-ion battery begins to burn hydrogen chloride, hydrogen cyanide, soot, oxides of nickel, aluminium, lithium, copper, cobalt, and hydrogen fluoride can be released, culminating in vapour clouds that are potentially explosive and hazardous to humans.

When these gases are released at the various stages of lithium-ion battery breakdown, there is a serious risk to those near it, especially in confined spaces such as on yachts.

Guidance Specifics

The information in the report is described as outlining best practices in the design, equipment, and outfit of spaces onboard that are dedicated to lithium-ion battery powered devices described as “small electric vehicles such as electric bicycles and kick bikes”. It is specifically written for li-ion batteries and craft, and is intended to increase safety for charging, handling, and stowage of them.

Batteries of other types and chemistries could present alternative risks while charging or stowing and additional measures may be needed depending on the characteristics of the battery in question. The guidance advises that a full risk assessment of any batteries may be needed before they are carried or charged on board.

The guidance is not intended for phone and laptop use and storage however they do point out that crew should be aware of the risks associated with these devices, especially when stored together with an aggregate capacity of batteries at more than 500Wh.

Alternatively, the guidance is intended for li-ion batteries with a capacity of over 100Wh (to align with the categorisation from UN3171 for use with electric vehicles of any type).

The report gives guidance on the size of batteries typically used in electric powered personal watercraft, which are:

• Electric Tenders: 40-100 kWh
• Electric Jet Skis: 20-50 kWh
• Electric Diver Propulsion Units (Bobs): 1-3 kWh
• Electric Foils: 1-5 kWh
• Electric Stand-Up Paddleboards (SUPs): 1-5 kWh

In comparison a small electric car will have a battery of 25 kWh and larger electric cars in the range of 60 kWh to 80 kWh.

It also details the fact that lithium-ion battery fires can be self-sufficient, burning even without access to additional oxygen, and may continue to produce high amounts of heat after fire-extinction which increases the risk of re-ignition.

The risk of fire is made even greater when a li-ion battery that is damaged, is exposed to the risk of saline penetration – as is highly possible with personal watercraft.

Measures to mitigate lithium-ion battery fire risks on yachts 

The report suggests that, wherever possible, the risk of charging and storing ‘electric personal watercraft’ such as jet skis and foils – as well as e-bikes and e-scooters for onshore use - should be considered at the early stages of the design and construction of yachts.

It does recognise that these devices can be added to existing vessels so operators should make provisions for these electrical supplies even if they are not required straight away.

An example of this would be the fact that manufacturers estimate that the minimum temperature in the battery where potential exists for thermal runaway to begin is between 60-70 degrees Celsius, therefore a means to monitor temperatures in spaces where the batteries will be held and charged should be included with integration into the ships alarms and control system wherever practical. The report details an ambient temperature of no more than 45 degrees Celsius.

They also detail the need for operators to continuously review their procedures and practices to uphold safe storage and operation of the equipment.

There is in depth guidance on how to store and charge lithium-ion batteries and associated equipment:

• Spare or removed batteries with a rating above 100Wh (0.1kWh) should be stored in a dedicated cabinet or locker constructed according to a recognised international standard
• All batteries should be stored, charged, and operated in accordance with the parameters set by the manufacturer, including operational instructions, maintenance requirements, temperature ranges and humidity limitations
• Damaged electric craft and electric batteries should be stored with extreme caution and should be unloaded at the first available opportunity for disposal or repair by a suitable land-based service provider
• Damaged batteries must not be charged, and any charging should be ceased immediately if damage occurs during charging
• Charging and storage spaces for Li-ion batteries should be temperature controlled or monitored to ensure that they are not too hot
• Batteries (in a vehicle or stored in a dedicated casing) should be kept as far away as is possible from petrol tanks or petrol driven craft
• Charging of batteries and battery operated vehicles should only be done inside the dedicated battery compartment or externally in accordance with the manufacturer’s instructions. Where batteries are removable, charging should be conducted in a dedicated charging station

Crew Knowledge and Fire Fighting

The guidance highlights the ‘critical’ need for crew to be made aware of the risks and trained and able to respond to lithium-ion battery fires, ensuring that the ship’s electrical supply to any battery being charged has been cut or isolated before any firefighting attempt is made.

Examples of this would be to share the knowledge that a damaged Li-ion battery causes rapid heating of the battery cells and will give telltale signs of it including hissing, whistling, popping, a sweet chemical smell, black ‘smoke’ (which is actually nanoparticles of heavy metals) and then white vapour coming from the battery or watercraft. If any of these happen, the crew should assume that the battery is heating and take firefighting measures that are appropriate.

After successful suppression reignition in lithium-ion battery fires is a risk so vehicles or craft containing them should be monitored by the crew (and further fire suppression action taken is possible) until the vehicle has been removed from the vessel.

The crew should be trained not only in firefighting measures but also in the proper handling, storage and charging of the electric watercraft and vehicles onboard, as well as being able to identify possible damage and knowing the procedures for disposing or quarantining of the damaged equipment.

The selected crew should also be fully trained and competent in the use of any specialist equipment such as Li-ion specific fire extinguishers, fire blankets, IR cameras etc. that are to be used in the detection or fighting of Li-ion battery fires.

It is recommended that a named person on-board is appointed as responsible for the maintenance, safe operation and response to emergencies that involve lithium-ion batteries – this could be the Safety Officer, Chief Engineer, or similar.

The report also details the recommendations for fire extinguishers on yachts and other related equipment:

• Minimum of 2 portable fire extinguishers, suitable for battery fires, outside the compartment or near the entrance
• An additional portable fire extinguisher on the large battery-driven vehicles or tenders
• A battery fire suppression blanket and/or containment bag
• Safe Operating Procedures should be included in the vessel’s Safety Management System and crew with specific duties involving battery equipment given adequate familiarisation and training to carry out these duties safely

To explore lithium-ion battery safety and extinguisher products, head to batteryfiresafety.com

The information contained within this blog is provided solely for general informational and educational purposes and is not intended as a substitute for professional advice. Before taking any actions based upon this information, we advise the reader to consult any and all relevant statutory or regulatory guidance and where felt necessary to consult a qualified fire or industry regulation professional. The use or reliance on any information contained herein is solely at the reader’s risk.

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