Marine Batteries

Marine batteries are crucial power sources designed specifically for underwater environments, powering a wide range of subsea applications. From unmanned underwater vehicles to deep-sea monitoring stations, these underwater batteries ensure the consistent operation of technology in some of the most challenging environments.

Subsea applications span scientific research, oil and gas exploration, defense, and renewable energy projects. With the increasing demand for deeper and more sustained underwater operations, the importance of high-performance marine batteries continues to grow.

Rechargeable Li-ion marine battery by SubCtech.

Types of Marine Batteries

Marine batteries are available in various types, each suited to specific subsea needs. The most common categories include lead-acid, lithium-ion, lithium polymer, and silver-zinc batteries.

Lead-acid batteries

Lead-acid batteries are traditional, reliable, and affordable energy sources that have been used in marine applications for decades. While they are cost-effective, they are large, heavy, and have a relatively low energy density. This makes them less suitable for applications where size and weight are critical, such as autonomous underwater vehicles (AUVs). Lead-acid batteries also require regular maintenance and have a shorter lifespan compared to more advanced options. Despite these limitations, they remain in use for applications where budget and space are less of a concern.

Lithium-ion batteries

Lithium-ion marine batteries have become the dominant choice for subsea applications, offering a higher energy density, longer life cycles, and lower maintenance requirements than lead-acid batteries. Their lightweight nature and compact size make them ideal for powering vehicles and systems in deep-sea environments where performance is key. These submersible batteries have become especially popular in AUVs and remotely operated vehicles (ROVs) that require extended operational times without recharging. Their efficiency and energy capacity make them critical for long-duration missions in remote and deep locations.

Rechargeable Li-ion underwater battery by SubCtech.

Lithium polymer and lithium iron phosphate (LiFePO4) batteries

Lithium polymer and lithium iron phosphate (LiFePO4) batteries are specialized versions of lithium-ion technology that offer improved safety, stability, and thermal management. These batteries are better suited for environments with high-temperature variations and are designed to withstand harsh subsea conditions. While slightly less energy-dense than traditional lithium-ion batteries, their improved safety profile makes them preferable for certain critical applications.

Silver-zinc and alkaline batteries

Silver-zinc and alkaline batteries are typically used for single-use or short-term applications where high power density is required. Silver-zinc batteries, although more expensive, offer excellent performance in high-drain applications and are used in deep-sea missions where quick bursts of energy are needed. Their compact size and high energy output make them ideal for specific subsea tasks, although their cost limits widespread use.

How Long Do Marine Batteries Usually Last?

The lifespan of a marine battery depends on several factors, including the type of battery, usage patterns, and maintenance. On average, marine batteries last between 2 to 5 years, but certain types can exceed this range with proper care.

Flooded lead-acid batteries, the most common and affordable type, typically last around 2 to 3 years. These batteries require regular maintenance, such as topping off electrolyte levels and cleaning terminals, to prevent corrosion and sulfation. Their longevity is often affected by how deeply and frequently they are discharged.

AGM (Absorbed Glass Mat) and gel batteries, which are sealed and maintenance-free, usually last longer, in the range of 3 to 5 years. These types are more resistant to vibration and can withstand deeper discharges without as much damage, making them ideal for harsh marine environments.

Lithium-ion marine batteries have the longest lifespan, often reaching 8 to 10 years or more. They offer high energy density, lighter weight, and better charge efficiency compared to traditional lead-acid batteries, but they come at a higher cost.

Several factors can shorten a battery’s life, such as frequent deep discharges, overcharging, and exposure to extreme temperatures. Proper maintenance, such as avoiding complete discharges, using a quality charger, and storing the battery in a cool, dry place during off-seasons, can significantly extend its lifespan. Regular inspections for signs of corrosion or damage also help ensure optimal performance and longevity.

Marine Battery Applications

Marine batteries play an essential role in powering various subsea applications, enabling the reliable and autonomous operation of underwater systems.

Autonomous Underwater Vehicles (AUVs)

AUVs are self-propelled, unmanned vehicles used for underwater exploration, seabed mapping, and data collection. These vehicles rely entirely on onboard batteries for power, as recharging is impossible during long missions in deep-sea environments. The lightweight, high-capacity nature of lithium-ion marine batteries makes them particularly suitable for AUVs, allowing for extended missions with minimal downtime. AUVs are deployed for scientific research, environmental monitoring, and industrial inspections, where reliable energy sources are essential.

Remotely Operated Vehicles (ROVs)

ROVS are tethered robots commonly used in offshore oil and gas operations for inspection, maintenance, and repairs. Although most ROVs receive power through cables from surface vessels, onboard batteries are increasingly being used to improve maneuverability and extend their operational range. Battery-powered ROVs are more versatile and can perform complex tasks without the limitations imposed by tethers. Additionally, these batteries act as a backup in case of tether failure, ensuring uninterrupted operation during critical missions.

Subsea monitoring and surveillance systems

Subsea monitoring and surveillance systems are deployed across offshore fields to track environmental parameters, monitor infrastructure, and ensure operational safety. These systems, often located in remote or hard-to-reach areas, rely on marine batteries to operate continuously. The data collected from these systems is vital for maintaining subsea installations and monitoring environmental changes over extended periods. Lithium-based batteries are the preferred choice due to their long service life and minimal maintenance requirements, reducing the need for frequent intervention in difficult environments.

Offshore energy production support

Offshore energy production support is another key area where marine batteries are essential. In the context of offshore wind farms and subsea energy facilities, batteries provide backup power for control systems, communication networks, and remote monitoring equipment. These batteries ensure that operations continue smoothly even during power outages or adverse weather conditions. With the growing adoption of renewable energy sources, marine batteries are playing an increasingly important role in stabilizing and managing these systems.

Marine Battery Challenges

Operating in subsea environments presents unique challenges for marine batteries. High pressure, extreme temperatures, and corrosive saltwater require batteries with robust design and specialized materials. Ensuring long-term reliability and safety in these environments is paramount. Modern marine batteries incorporate pressure-compensated designs and corrosion-resistant materials to overcome these challenges. Innovations like solid-state batteries and advanced thermal management systems are being developed to further improve the performance of subsea energy solutions.