Development of a pressure tolerant Lithium Sulfur battery pack for Marine Autonomous Systems (MAS)

01.04.2017
The MAS project is a two year programme, supported by Innovate UK and DSTL, to develop a pressure tolerant battery pack capable of powering autonomous vehicles to ocean depths of 6,000m using next generation Lithium Sulfur cells.

With just 6 months remaining until completion, the consortium, led by Steatite, and consisting of OXIS Energy, MSubs and the National Oceanography Centre (NOC) has made tremendous advances in battery capability through extensive design and testing. The project is now moving towards full open water trials in two deep dive vehicles.

Battery development
A number of 24V 600Wh battery units are currently being produced, and will undergo further tests in the NOC pressure chambers.

The prototype packs consist of 24 Oxis Energy Li-S cells in a 12S2P arrangement controlled by Steatite's multi-chemistry Battery Management System. The packs each occupy a volume of around 7 litres and will be used in different combinations in the upcoming tests and trials to confirm the capabilities of the system. Further design optimisation will reduce the pack volume in preparation for production. A flexible and extendable system design ensures that batteries can be customised for optimal integration and performance for each application.



Open water trials
During the Summer of 2017, these prototype packs will be integrated into submersible systems for trials. Two different UUVs will be deployed representing distinct mission profiles and energy requirements.

The NOC's Autosub Long Range, which is optimised for low-power long-endurance missions, and the Deepbots system, a vehicle capable of taking higher-draw payloads to significant depth under autonomous operation.

Battery Management System
A major aspect of the MAS project is the development of Steatite’s Battery Management System (BMS). This ground breaking BMS and associated charger technology is pressure tolerant and capable of use with all mainstream battery chemistries, including the latest Lithium Sulfur cells in a highly scalable set of series and parallel combinations.

One BMS PCB can be used with any combination of cells up to 35V and 30A continuous. To scale beyond this level an additional BMS board is added each time voltage and current limits are reached for each sector.

Any number of BMS boards can be added, with a nominated board acting as a master controller. This provides a single interface regardless of the size of the system.



Looking ahead
The project continues to progress at pace. Cell and BMS testing have successfully advanced to a point where a number of prototype battery packs can be constructed and integrated into UUV’s for open water trials.

Following these vehicle trials in mid 2017, the technology will be made production capable, capitalising on Steatite’s custom build capabilities which will enable Li-S battery packs to be seamlessly integrated into a range of diverse applications.

Although the focus of the project is firmly on developing a prototype battery pack for marine and oceanographic applications, the sectors in which this technology can potentially be implemented are far reaching, including areas such as energy storage, unmanned and autonomous systems.

The inherent safety of Li-S cells combined with superior Wh/kg, greatly increased pressure and temperature tolerances, 100% depth-of-discharge, and more environmentally friendly chemistry make Li-S a dependable alternative to existing chemistries, such as Li-ion.



It is these significant benefits that the project is successfully optimising and pairing with our all new BMS, to produce a new generation of battery systems.

Advances in cell energy density beyond the recently announced 400Wh/kg level, together with further optimisation of the battery pack design, mean we are on target to achieve robust energy systems with improvement in gravimetric energy density for underwater applications over the most capable Lithium-ion alternative by a factor of between 2 and 3.
To receive more detailed updates on the MAS battery project please register at www.steatite.co.uk/masupdates


Location: UK









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