Resilient to heavy loads, longer lasting, smarter and, some would argue, cheaper over the long term; lithium batteries technology is now becoming more mainstream on yachts.

Used not only for house batteries, lithium also powers propulsion on some new models. Many cruisers now have capacity to live aboard a yacht in a similar way to a house, with far less power restriction.

The MCA recently issued a guidance note on lithium battery installation to give a framework for best practice. While the advice leans towards commercially coded yachts, it highlights more general concern around lithium technology.

Since lithium has become more mainstream, there have been a number of fires on yachts, some causing a total loss. The note covers key aspects including installation process, system design, ventilation and cooling – all potential vulnerabilities of a lithium system. The message overall is that a lithium installation, whether retrofit or on a new build yacht, should be taken seriously.

Large solar arrays are often used as a means to top up or trickle charge lithium batteries. Photo: James Mitchell/WCC

Getting it right

At present, the only type of lithium batteries approved for installation on yachts are Lithium-Iron-Phosphate or LFP. Whilst it might be tempting to use cheaper lithium varieties such as nickel or cobalt, these are far more vulnerable to thermal runaway – an uncontrolled series of reactions which cause a rapid increase in temperature, and often an uncontrolled fire.

Installing batteries incorrectly can automatically invalidate your yacht’s insurance policy. What constitutes a correct installation is more layered than with older battery technology, but insurance companies have been clear they’re not inherently opposed to owners using lithium. High current levels, a need for safe containment in case of failure and the need for a proper battery management system mean that it’s important to seek expert advice and/or installation.

A knowledge gap

William Taryn was a firefighter in both California and Mallorca before starting to teach firefighting to yacht crew. He now has his own fire safety training business in Palma, Maritime Safety Solutions, while remaining a serving firefighter in the city. Over the past few years he has become heavily involved in yacht lithium battery safety.

“As lithium battery systems started to be installed on yachts, we began to see fires here in the city. We quickly learned more about lithium technology and what leads to lithium fires. There are lots of aspects to having lithium on board a boat and it’s not just the yacht’s batteries, as many yachts now carry things like e-bikes with lithium batteries, and the storage of them has to be considered too. “Put simply, lithium technology is in all sorts of things that you might find on board.”

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Taryn’s business now consults to yachts built with lithium battery systems, including training their crew, developing operating manuals and systems for each specific yacht. A 47m hybrid yacht, capable of running entirely on battery power, was the first of these consulting projects.

“We looked at the battery rooms in detail, then developed a set of procedures the crew could work with to keep things safe. It’s quite layered on such a big yacht and the emergency procedures specific to the batteries need to be understood by all crew.”

Taryn worked with crew training and recruitment company Bluewater Yachting to lobby for changes to the STCW course for professional crew. Thanks to their efforts, it will soon include a firefighting section on lithium.

DIY lithium systems should involve a marine electrician to ensure suitable installation. Photo: Will Bruton

An impact study

In February last year INEOS Britannia’s AC40 suffered an on-board fire during training off Barcelona. While sailing the crew had to react quickly to smoke pouring out of a forward hatch. They and their chase boat deployed fire extinguishers, followed by water being pumped in through the forward hatch, and were fortunately able to contain the fire.

The culprit was a lithium battery that had experienced what’s known as ‘thermal runaway’. Taryn soon found himself tasked with investigating. “In that case the battery fire had effectively been caused by repeated impact. Those yachts bounce around a lot and an excess of this had caused thermal runaway which, once it starts, is very hard to stop,” he explains.

Other incidents have been more extreme. In July 2023 a lithium battery fire at a marina in the Florida Keys caused one death and led to two people being critically injured. An e-bike kept on board a yacht had fallen in the water earlier in the day. The battery had then been stored in a wooden cabinet containing flares.

The British America’s Cup team’s AC40 yacht suffered a lithium fire on board, which the crew was fortunately able to contain at sea. Photo: Ugo Fonola/America’s Cup

And a lithium battery fire was suspected to be the cause of the deaths of two cruisers found deceased in their lifeboat in British Columbia in 2022. The couple – Canadian Brett Clibbery and Briton Sarah Packwood – were crossing the Atlantic on their Gib’Sea 42 Theros.

No distress call was received from Theros, but one crew was found wearing a flotation suit that was seriously fire damaged. Theros was understood to have been retrofitted with an electric car battery.

Taking precautions

The STCW (Standards of Training, Certification and Watchkeeping for Seafarers) is a framework for commercial operations that has now evolved to take lithium technology into account, but what practical steps might be taken for leisure sailors? Correct installation is crucial, explains Taryn.

“Consideration of how the batteries are contained, how they are isolated, how they are ventilated, and how they might be extinguished are all important to think about.”

Proteng fire sticks can put out any material that has ignited

One challenge is how the extinguishing system actually fits in. “Since I started to get involved with improving safety around lithium on board, one product has really stood out to me,” Taryn says. The Proteng fire suppression system can be fitted into battery spaces and requires no wiring. It activates above a certain temperature, shattering its own polymide container, at which point the retardant liquid becomes a gas and covers everything in a fine film.

Build challenges

So, if using lithium is so loaded with safety considerations, why do it? The upsides are big. Batteries can cope with heavy loads, making them well suited to a yacht equipped with creature comforts; even air-conditioning systems can be run relatively directly from the batteries.

Battery life cycles are much longer, balancing out their much higher initial purchase cost. The challenge the industry and owners face is in making sure installations meet the more exacting requirements of lithium. Battery compartments must be carefully thought through, considering how they are ventilated, but also how they might contain a fire should it occur.

Lithium battery systems are capable of supplying high current instantly. Photo: Mastervolt

Whilst this is relatively straightforward for new build yachts, it’s much more complex for those retrofitting lithium; a straight swap into the same location may not be possible. The MCA guidance note is likely to shape the framework that flag states considering regulation adopt. This means commercially coded yachts may need to invest to meet regulatory requirements for lithium technology on board. It’s a factor to consider for any owners considering charter.

For one major luxury yacht builder we talked to, who didn’t want to be named, it has proved a significant challenge for yachts already in build. “For anyone looking to install lithium, the simplest and most straightforward advice at this stage is simply to do it properly, taking note of the points raised by the MCA guidance note, while using an experienced and qualified electrician,” explains Taryn.

Top tips for a safe and effective lithium battery installation

1. Choose the right chemistry – Stick to LiFePO₄ (Lithium Iron Phosphate). It’s the most stable, with a lower risk of thermal runaway.
2. Install a proper battery management system (BMS) – A robust, marine-rated BMS is non-negotiable. It should handle cell balancing, over/under-voltage protection, temperature monitoring, and disconnects. Opt for systems with independent cell-level monitoring rather than just pack-level.
3. Ventilation and location – Install batteries in a cool, dry, and well-ventilated space. Lithium doesn’t off-gas under normal use, but airflow helps keep temperatures stable.
4. Overcurrent protection – Fit correctly rated fuses and breakers as close to the battery as possible. Lithium can dump huge currents instantly – far more than lead-acid – so cable and fuse sizing is critical to avoid electrical fires.
5. Separate charging profiles – Ensure all chargers (shore power, alternator regulators, solar controllers, wind generators) are configured for lithium. Overcharging or floating at lead-acid voltages will shorten battery life or cause failures.
6. Alternator protection – Lithium’s low resistance can burn out a stock alternator. Install a DC-DC charger or external alternator regulator to ensure safe charging limits.
7. Temperature safeguards – Never charge lithium below 0°C – this causes lithium plating and can lead to failure. Ensure the BMS has low-temp cut-off or install heating pads in colder climates.
8. Cabling and connections – Use properly crimped marine-grade cables with no undersizing. Poor connections can overheat under lithium’s higher loads. Keep runs short and secured against chafe and vibration.
9. Redundancy and manual override – Consider a manual disconnect switch or emergency isolator that bypasses electronics if the BMS shuts down in a critical situation at sea (while still keeping fusing in place).
10. Follow standards and best practice – Refer to ABYC E-13, ISO 13297, and manufacturer installation guides.

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