Development and Experience of a Practical, Pressure-Tolerant, Lithium Battery for Underwater Use
For a number of years, lithium-ion batteries have promised energy and power densities that make them an attractive alternative to the silver-zinc batteries historically used in underwater vehicles. For AUV (Autonomous Underwater Vehicle) application, polymer-electrolyte cells offer the promise of pressure tolerance; this key attribute impacts vehicle design and operational logistics in a number of ways. Primarily, it facilitates the design of arbitrarily large battery packs by obviating many of the problems associated with large, heavy and expensive pressure vessels that would have been otherwise required to house batteries at depth. This allows a single AUV operator to recover the vehicle and remove and replace the batteries in minutes without the down time associated with servicing o-rings and seals. In a military context, this new operational paradigm has made back to back search and classify missions a practical reality. As with all new technologies there is a hiatus between availability, practical implementation and adoption. Many fundamental, logistical and practical engineering problems in design and manufacture have been solved in the past 5 years leading to a range of commercially available batteries with power densities exceeding 100Wh per neutrally buoyant Kg. This paper will explore these challenges, examining specific solutions derived from experience gained through the pressure testing of over 20,000 cells
Pressure-Tolerant Batteries for Autonomous Undersea Applications
Abstract : High performance power sources constitute a critical technology for our core business -- developing and building autonomous underwater vehicles. As these vehicles reach new levels of autonomy and reliability, and as their areas of application expand, the demand for improved energy supply grows continually. Using emerging Advanced Lithium Battery technology, Bluefin set out to advance the state of the art in subsea energy storage in the following areas: (a) Energy density with respect to weight and volume, including all housings, cabling, and support electronics and at temperatures typical of the sub sea environment; (b) Safety , user friendliness, and robustness in handling, operation, storage and shipping, charging (c) AUV design freedom and scalability to high energy requirements, no restrictions on vehicle attitude in operation etc.; (d) Ultimate life and life time cost of batteries. Our goal was to build a practical, high performance battery at a reasonable level of technical risk, for use in our own vehicles, as well as for sale to other subsea industries. The longer term goals include expanding into other markets, as well as continual technical advances that exploit the expected improvements in price, performance and safety of these cells. Consumer applications for these cells will drive availability up, price down, and performance ever closer to the theoretical limits in the years ahead.
The experience and limitations of using manganese alkaline primary cells in a large operational AUV
The authors describe how the use of manganese alkaline batteries for the Autosub science programme has enabled the project to progress swiftly from being a technological demonstrator to providing new ways of gathering environmental data not possible by other methods. Throughout the programme, all areas of the battery system have undergone development. that is: specification, design and manufacture of the pack; inspection and testing; packaging, storage and physical handling; electrical and thermal insulation; estimates of remaining endurance; and disposal of depleted packs.