SBIR-STTR Award

It has long been known that batteries can be pressure compensated, i.e., modified to operate at depth [e.g., Work, 1968]. Unfortunately, these modifications bring along severe restrictions on vehicle handling as well as increased maintenance requirements, neither of which is acceptable for the new generation of small, low-cost, AUVs. Recent advances in polymer- electrolyte and all-solid-electrolyte lithium ion cells open the possibility of pressure-tolerant batteries, i.e., batteries that are intrinsically capable of withstanding the pressure with negligible modification. In this proposal we will demonstrate how such pressure-tolerant batteries can increase an AUV's energy capacity by 50% or more, with no reduction in vehicle payload and no increase in vehicle size. To get a corresponding increase in capacity through better electrochemistry or cell manufacturing would require many millions of dollars and many years of R&D effort, with no guarantee of success. For this Phase I effort we propose to perform the key tests required to demonstrate the feasibility of such pressure-tolerant batteries.

Benefits:
This work will result in significant increases in the effective energy density of underwater battery packs. Such systems will power AUVs in scientific and military applications, as well as the critical off-shore oil and sub-sea telecommunications industries. Our market study show that, by 2005, AUV applications alone will constitute a multi-million dollar market for these batteries. In addition, the prospects for non-AUV uses are at least as promising.

Keywords:
Autonomous Underwater Vehicles, Solid Electrolyte, Lithium Polymer, Pressure Tolerant, Pressure Compensation, Marine Power, AUV, battery

Recent advances in battery technology open the possibility of pressure-tolerant batteries, i.e., batteries that are intrinsically capable of withstanding ambient pressure in the open ocean with negligible modification. Pressure-tolerant batteries can increase an AUV's effective energy capacity by 50% to 100%, with no reduction in vehicle payload and no increase in vehicle size. To get a corresponding increase in capacity through improvements in electrochemistry or cell manufacturing would require investing many millions of dollars over many years, with no guarantee of success. In our Phase I effort we performed the first systematic testing of appropriate cells under deep ocean ambient pressure. Our results are promising. COTS cells underwent many electrical cycles at high rates (nominally C/2) while under isobaric conditions of over 6,700 psi, with no evidence of pressure-induced failures in either set of cells. Thus, there exist today COTS cells that can be used to build a high-capacity pressure-tolerant battery pack for Navy vehicles. For our Phase II effort we propose to engineer a pressure- tolerant battery pack based on the current state-of-the-art COTS cells. Furthermore, the pack will be designed to allow it to readily accept improved cells as they become commercially available

Keywords:
Batteries, Auv, Ocean, Marine, Energy, Pressure, Compensate, Bluefin