Solid-state battery reaches the sea with DNV approval and promises an end to fire risk

Ask any shipyard, marina or insurer what the biggest brake on vessel electrification is and the answer will be neither range nor price. It will be fire. In the United Kingdom, the Marine Accident Investigation Branch, MAIB, attributes about 40% of yacht fires in recent years to lithium batteries. The problem has a technical name, thermal runaway: a damaged, overcharged or badly installed cell heats up, releases flammable gas and contaminates its neighbour, in a chain reaction that continues even after the flames seem under control.

That is the scenario Denmark's EPTechnologies wants to change with SVENNER, presented in November 2025 as the world's first solid-state marine battery with type approval from DNV, the Norwegian classification society, under notation NR TAE000054J. In September 2026 the product was at SMM in Hamburg, Europe's largest maritime technology fair, and it is already sold to order.

What changes inside the cell

A conventional lithium battery uses a liquid electrolyte, and it is that flammable liquid that feeds the fire when something goes wrong. In solid-state technology, most of the liquid electrolyte is replaced by solid materials. The cell is still lithium, but the fuel for the fire is taken out of it.

The test figures show the scale of the change. SVENNER withstands six times the overcharge without a thermal reaction and puncture by an 8 millimetre nail without catching fire. Under DNV's classification it meets Design Option 1: a thermal incident stays contained inside the module itself, which removes the gas exhaust ducting required in conventional installations. For anyone designing a boat, that is less space, weight and installation cost.

Service life and the long-term maths

The second argument is durability. The manufacturer speaks of more than 10,000 charge cycles at 80% depth of discharge, against 2,000 to 4,000 for a conventional lithium battery. On a ferry, a tug or a workboat that charges every day, the difference shows up as years of operation before the battery bank is replaced, which is why the cycle-life warranty is five years.

Each module delivers 16.1 kWh at 51.2 volts, weighs 111 kg and measures 810 by 425 by 250 millimetres, in an aluminium case with IP55 protection, or IP67 on request. It charges and discharges at 1C, that is 314 amps continuous, with peaks of 350 amps for 15 minutes, and operates from minus 10 to 60 degrees Celsius. Modules combine into racks for ferries, workboats, performance yachts and hybrid systems, in new builds and retrofits alike.

The management electronics were also designed for the sea: a battery management system with a redundant dual-core processor, high-voltage interlock, water-leak detection in every module and a physical switch that lets the crew override the protections manually in an emergency, when power is needed at any cost.

What the battery does not yet deliver

It is worth separating promise from product. The great theoretical advantage of solid state, energy density of 400 to 500 Wh per kilo against 250 to 300 for today's best lithium cells, is still a laboratory target. On the current module's numbers, 16.1 kWh in 111 kg gives about 145 Wh per kilo at pack level, in the range of good lithium iron phosphate marine batteries. In other words, whoever buys SVENNER today buys safety and service life, not a lighter boat. The second-generation model, due in January 2026, promises 12% more performance in the same dimensions and weight. Price and charging time have not been disclosed.

The company behind it

EPTechnologies was founded in 2013 by Kasper Falkenberg in Sønderborg, in southern Denmark, and has had Marco Ottiker as co-owner and chief operating officer since 2018. For Ottiker, DNV type approval is a breakthrough for marine electrification, because it gives designers and operators a complete energy-storage solution that combines safety, durability and performance.

For the Brazilian market the message is direct. The electrification of workboats, ferries, support vessels and marina service launches runs into the distrust of owners and insurers over fire risk. A battery that passes the nail test, carries class certification and needs no gas exhaust changes the conversation when the project and the policy are approved. It is the kind of component the Ocean Economy will start to specify.