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Lithium batteries have become a popular choice for powering boats and have been labelled as a practical substitute compared to other forms of batteries.

However, safety concerns are a major limitation of the new advanced power source. If not handled or stored correctly they could cause a catastrophic fire.

The biggest danger comes whilst charging these batteries. Many are charged overnight and so are left unattended. This creates the risk of overcharging, which can cause thermal runaway resulting in a disastrous blaze.

Another issue is that the safety approach to batteries whilst at sea is different to that on land. Imagine a vessel getting slammed with waves, sometimes at a very high frequency when the weather is rough. The vibrations can eventually lead to structural damage of the battery casing, potentially triggering a short circuit. Not to forget that the time taken to reach a burning ship is longer than on land.

In an unsettling report made by the European Union, scientists conclude that a lithium-ion battery fire on board a ship can be more deadly than a sinking ship.

Another shocking fact is that a lithium-ion battery fire is one of the most dangerous and difficult fires to control and extinguish. A traditional fire suppressor system is not effective on a lithium battery fire and could potentially make it worse.

So why are they increasing in popularity?

Lithium batteries have been reported to be more efficient and sustainable. Compared to lead-acid batteries, lithium batteries weigh less, have higher energy density and last longer.

In addition, lithium batteries typically have a longer lifespan compared to lead-acid batteries – they last between three and five years. This means lower maintenance and replacement costs for boat owners.

An important consideration for boat owners is weight, and lithium batteries are significantly lighter compared to other batteries.

Lithium batteries can retain their charge for longer periods of time when not in use, and this is extremely beneficial to boats that are not used frequently. They can also handle high discharge rates, which means they can deliver more power quickly when needed.

In both hot and cold conditions, lithium batteries can operate in a wide range of temperatures. This is important for marine applications where temperatures can fluctuate widely.

Lithium batteries require little maintenance, making them easier to use and care for. They are more eco-friendly compared to lead-acid batteries as they don’t contain toxic chemicals, and they can be recycled.

Let’s not forget about the lethal limitations…

Aside from the advantages, lithium batteries are far more expensive due to their cost to produce. This can be a significant consideration for some boat owners.

Another disadvantage is the limited availability of charging infrastructure in the marine and boat industry. Many marinas don’t have the necessary equipment to charge lithium batteries, which can make it difficult for boat owners to find a reliable charging location.

Most importantly, safety is a huge concern. Mike Schwarz, IIMS CEO warned: “It is a massive and worrying subject and one that is consuming the finest technical minds in the marine world right now.”

It’s reported that firefighting systems are not yet developed sufficiently to extinguish lithium-ion battery fires in most cases. A lethal amount of unignited toxic gases, which hang around at low levels, can also go undetected and ignite, or worse, simply kill.

How is it being managed?

Regulators are still grappling with the lithium battery dilemma and attempting to understand the correct regulations to implement.

Educating people on the dangers of lithium batteries and encouraging them to risk assess properly is the current answer.

Here are some tips:

  • For all batteries onboard, stick with one battery chemistry. Each battery type requires specific charging voltages and mixing types can cause under or overcharging.
  • Never mix old batteries with new ones in the same bank. Old batteries tend to pull down the new ones to their deteriorated level.
  • Disconnect your battery when not in use.
  • At the beginning of the season, charge and check batteries for connection and corrosion. At the end of season, remove batteries for storage, clean top surfaces, grease terminal bolts and store in a dry, cool area.

The Joint Hull’s Yacht sub-committee chaired by Emily Grew has also released a Lithium Clause to assist underwriters in the assessment of yacht risks where such batteries are present.

At Arc Legal, we offer bespoke Marine Legal Expenses Insurance for owners, skippers, crew, and guests of vessels. Cover includes the provision of 24/7 legal advice from a team of specialist marine lawyers.

We cover uninsured loss recovery and personal injury on board the boat, contract disputes connected with the boat, navigational prosecution, emergency accommodation and repatriation expenses if the boat is damaged, mooring fees if the boat can’t be used, and replacement charter costs if the boat can’t be used for a booked trip.

We’re proud to say that Arc Legal are the leading provider of LEI to the boating community, working with most major boat insurers.

For further details on our Marine Legal Expenses Insurance for skippers, crew, and vessel guests, please contact your Partnerships Manager or email


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