SubCtech GmbH, founded in 2010 by applied physicist Stefan Marx, has positioned itself as a global leader in advanced underwater energy solutions. Based in Kiel, Germany, SubCtech specializes in subsea power systems and batteries, custom engineering, and rigorous prototype validation for a wide range of subsea applications. With a growing team and expanding global reach, the company delivers smart, field-tested systems that reduce CAPEX, OPEX, and CO2 emissions—a win for industry, security, and sustainability.
ADAPTABLE OCEAN POWER
SubCtech’s Ocean Power product line includes lithium-ion battery systems and energy storage solutions for:
- Offshore Oil & Gas, Carbon Capture & Storage (CCS)
- Environmental Monitoring
- Autonomous and Remotely Operated Vehicles (AUVs, ROVs, USVs)
At the core of this portfolio is the Power- Packs™ line—robust, long-lifespan battery systems (up to 25 years) that power everything from portable sensors to large-scale underwater platforms.
Engineered for operation in harsh subsea environments, the PowerPacks™ come in a variety of pressure-tolerant housings including:
- Titanium: for ultra-deep missions up to depths of 6,000 m
- Super-Duplex Stainless Steel: rugged and corrosion-resistant, also up to 6,000 m
- Marine-grade Aluminum: optimized for shallower operations up to 1,000 m
PROVEN IN THE FIELD
SubCtech’s battery systems undergo extensive qualification testing—including resistance to shock, vibration, thermal variation and electromagnetic interference. All systems are built to meet or exceed:
- UN T38.3 (transport safety)
- API17F/API17Q (subsea equipment reliability)
- MIL-STD, DNV 2.7-3 (portable offshore units)
The Li-ion-based PowerPacks™ offer automatic protection against overvoltage, undervoltage, overcurrent, overheating, overcharging, short circuits and smart algorithm for complex ESS systems. An intelligent Battery Management System (SmartBMS™) constantly monitors and optimizes performance from individual cells to full module arrangements. These systems also support remote diagnostics—enhancing reliability while minimizing downtime.
The PowerPacks™ can deliver high peak currents, operate in sub-zero temperatures, and support long-term deployments with minimal maintenance.
SUBSEA ENERGY STORAGE SYSTEM
A major milestone for SubCtech is the development of a modular, scalable Subsea Energy
Storage System (ESS)—the first of its kind to be certified under API17F and reach TRL 6 (Technology Readiness Level 6) and thus validated under real-world offshore deployment conditions.
The ESS includes:
- Two 1 MWh Battery Storage Skids (BSS)
- Integrated Power Skid (AC/DC converter)
- Auto-configuration via SmartBMS™ and BCM (Battery Control Module based on NetDI® technology)
- Redundant architecture for continuous operation
- Modular expansion for up to 6 MWh capacity
Built for a 25-year lifespan, the ESS currently allows 2,000 m deep deployments, with possible upgrades allowing 3,000 m or 6,000 m depths. The system has already been successfully implemented in the oil & gas sector followed by an immediate reorder confirming its value and dependability.
FLEXIBLE POWER APPLICATIONS
SubCtech’s vehicle batteries and subsea systems support a wide range of defense and industrial use cases:
- XXL-AUVs for surveillance, mine detection, and deep-sea intelligence (up to 12 modules at 100 kWh each, totaling >1 MWh at up to 1,000 V, in serial or parallel configurations)
- AUVs with 416 mm, 310 mm or 260 mm diameter battery modules for underwater inspection or monitoring
- Docking-enabled AUVs and ROVs, autonomously charging at seabed stations without the need for surface recovery
The ESS also provides buffering for renewable energy sources like wave, wind, and solar power and powers subsea compression, injection, and monitoring equipment—key to the offshore energy transition.
ENGINEERING FOR EFFICIENCY
By minimizing the need for vessel-based operations, SubCtech’s systems dramatically reduce both operational costs and emissions. The ESS can replace long umbilical connections, reduce cable infrastructure (especially long tiebacks or CCS) and extend autonomous deployment durations—all while maintaining high safety and reliability standards.
The redundancy concept ensures uninterrupted supply to critical subsea loads. The use of smart telemetry systems enables wireless underwater communication of up to 6,000 m via Acoustic Telemetry Modems (ATM).
GLOBAL GROWTH, LOCAL EXPERTISE
With 88 employees and tripling production expansion in early 2026, SubCtech continues to scale responsibly. Their UN-certified battery systems are airfreight-compatible and shipped globally, supported by a professional international sales network.
Our mission is to provide sustainable technologies for the marine environment. With our proven battery and ESS platforms, we’re enabling the energy transition while supporting strategic subsea operations around the world.
This feature appeared in ON&T Magazine’s 2026 January Special Edition, The Future of Ocean Technology Vol. 6, to read more access the magazine here.
