A Saft HEL 14-1920 lithium battery is currently providing power to the
first node of a seismic network installed on the floor of the Ionian Sea,
some 2,000m below the surface where the water pressure is in excess of
210 atmosperes. The node, which is designed to operate autonomously for
200 days, has been submerged since October last year and its battery is
reported to have operated reliably at this extreme depth.
The nodes are being constructed for Italy's National Institute for
Geophysics and Vulcanology (INGV) by the Italian offshore engineering
group, Tecnomare. Each weighs 1,500kg at sea level (about half this when
submerged), and contains a variety of sensors. Along with its four Saft
lithium-thionyl chloride batteries (containing more than 400 cells), its
components include a broadband seismometer, gravitometer, hydrophone,
current meter and a sensor that measures local physical parameters such
as conductivity (salinity), temperature and depth/pressure.
While during the initial stages of the project, the nodes remain
autonomous, they will eventually be linked back to the shore via a subsea
cable. The Saft batteries will then take on a back-up role, providing
power for basic functions, including data acquisition and local data
storage.