Energy storage batteries for marine applications face unique challenges: saltwater corrosion, constant vibration, temperature fluctuations, and the need for high reliability in remote, maintenance-restricted environments. These batteries power everything from trolling motors and navigation systems on recreational boats to critical systems on commercial ships, requiring designs that balance durability, energy density, and safety. Marine batteries must also comply with strict regulations (e.g., US Coast Guard, ISO 8846) to prevent fire or explosion risks in enclosed, fuel-rich environments.  

Deep-cycle lead-acid batteries have long been the workhorse of marine energy storage. Flooded lead-acid batteries offer high capacity at low cost, suitable for large vessels with dedicated maintenance crews, but their need for periodic electrolyte refilling and risk of acid spills limit use in recreational boats. Sealed AGM and gel batteries are preferred for their maintenance-free operation and resistance to vibration, which is critical in rough seas. A typical sailboat might use a 12V AGM battery bank with 200–500 Ah capacity to power electronics, winches, and overnight systems, while commercial ships may employ megawatt-scale banks for auxiliary power.  

Lithium-ion batteries are transforming marine energy storage, particularly in electric boats and hybrid vessels. Lithium iron phosphate (LFP) batteries offer 3–5 times the cycle life of lead-acid, with 80% DOD without degradation, enabling smaller, lighter systems that save fuel (in hybrid setups) or extend electric range. For example, an electric ferry might use a 400 kWh LFP battery pack to achieve 100 nautical miles per charge, with fast-charging capabilities at ports. Their low self-discharge rate (1–2% per month) is ideal for boats that sit unused for periods, and BMS systems monitor voltage and temperature to prevent overloading.  

Marine batteries must undergo rigorous testing for saltwater resistance. Enclosures are made of corrosion-resistant materials like stainless steel or fiberglass, and connectors are sealed to prevent moisture ingress. In hybrid systems, batteries integrate with generators and renewable energy (e.g., solar panels on decks) to optimize energy use, reducing fuel consumption and emissions. As the maritime industry pushes toward decarbonization, energy storage solutions will play a pivotal role in electrifying vessels, with advanced lithium systems and robust lead-acid variants coexisting to meet diverse operational needs—from small fishing boats to massive container ships.