Is it safe to bring electric cars on ferries?

Q. A reader asks: Any restrictions on taking an EV on a car ferry?
A. No, not really, although some specific ferry companies do ask you not to charge on board.
Actually, charging on board a ferry – which would obviously make huge sense from the electric car driver’s point of view – is a relative rarity thus far.
According to Stena Line spokeswoman Nicola Abernathy, the company has no restrictions when bringing an EV on the ferry.
“Stena Line continues to engage in research and with working groups regarding lithium-ion battery safety,” Abernathy said. “Stena Line is currently trialing charging on board on a small scale in other regions. However, this is still at an early stage and we currently do not have any plans to introduce it on the Irish Sea.”
Stena Line says it works with the European Union-funded Lashfire project, which has brought together experts in fire safety and shipping to try to come up with solutions for the potential problems of an electric car battery fire on board a ship.
Electric car fires are rare – staggeringly so. According to the Swedish Myndigheten för Samhällsskydd och Beredskap (MSB, or Authority for Social Protection and Preparedness), 29 EVs and 52 hybrids caught fire in Sweden between 2018-2022. The average number of fires each year involving EVs in Sweden stands at 16, a figure grouping hybrids and full battery EVs together. In total, about 3,400 passenger vehicles catch fire each year in Sweden, which means that a mere 0.4 per cent of all passenger vehicle fires there annually involve an electric or electrified car. Basically, you’re much more likely to be at risk of a fire with a petrol or diesel car than with an electric one.
Nonetheless, fire on board a ship at sea is potentially disastrous, and so a touch of caution remains in the air when it comes to EVs and ferries. Why? Because once one starts, an EV fire can be very difficult to put out. Because of that potential threat – however statistically unlikely it may be – ferry operators such as Brittany Ferries and DFDS have at times imposed bans on electric cars charging while on board – when a battery is under load, while charging, it’s at its most potentially vulnerable to any fire risk.
While the risk is there, plans are being put in place to tackle any EV fires on ferries. The Confederation of Fire Protection Associations Europe (CFPA-Europe) is a pan-European group which offers advice and training on tackling fires, and carries out research into the best practices.
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When it comes to electric cars and ferries, the CFPA worked with the DBI – the Danish Institute of Fire and Security Technology – to test some techniques for quelling EV fires in the confined spaces of a ship at sea.
Following the tests, Alexander Kleiman, maritime research and development project manager at DBI Advanced Fire Engineering, cautioned that while no two fires are ever quite alike, there are some basic techniques which can be used to deal with the problem.
“Sprinkling with water mist proved highly effective. Not to extinguish the fire, but to limit the spread of the fire, so that the crew can get there and put out the fire using traditional extinguishing methods,” Kleiman said. “All the fires in our tests were extinguished, but this required professional firefighters. It is known that a fire in an electric car battery can flare up again, so extinguishing it completely can be a lot to expect from a ship’s crew who have only been on a few mandatory maritime fire safety courses.”
Kleiman said that using a heavy quartz-impregnated blanket to smother an EV fire might be the best way to tackle any on-board issues, albeit this will require the vehicles on the ferry’s deck to be parked well apart from one another. On foot of the DBI and CFPA’s recommendations, we may see some changes to car ferry design in the coming years to allow more space around electric cars so that any fire which does occur can be more easily brought under control.
Kleiman was also quick to dispel some rumours and half-truths about EV fires on board a ship. He said that it was extremely unlikely that the heat from a battery fire could compromise the strength of the steel or aluminium deck of the ship, unless a car was left to burn unchecked for several hours. Equally, he said that electric car battery development has made them much, much safer.
“When we short-circuited the battery cells in a Renault Fluence, the whole battery caught fire. When we ignited it in a newer Tesla model 3, only the battery cell affected caught fire. Secondly, the positive message is that fires in electric cars on board ferries are manageable and not something we need to fear. All the fires in our tests could be extinguished, so with the correct firefighting technologies on board, the correct training of the crew and well-co-ordinated collaboration with the onshore emergency services, electric cars should not pose a safety problem in ferry traffic,” Kleiman said.
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Some ferry operators in Greece have introduced a charge limit for electric cars when boarding a service – the maximum that the battery is allowed to be charged to is 40 per cent, with the Greek ministry of shipping and island policy saying that batteries with high charge levels are more likely to experience fire and thermal runaway incidents. No ferry operator in Irish waters has yet introduced any such restriction, and it’s worth pointing out that in Greece, similar restrictions apply to cars fuelled by LNG or CNG gas.
Equally, any restrictions which are in place for bringing an EV on to a ferry will likely be reduced once solid-state and lithium-iron phosphate batteries become more common – both designs are thought to be at a significantly reduced level of risk when it comes to fires.