At first, alkaline chemistry seemed a logical choice for this system: It was relatively inexpensive and easy to both transport and dispose. But engineers needed more from their power source for this mission-critical application. Although the up-front cost of Alkaline was low compared to other chemistries, there was a significant portion of the research budget spent on the logistics of replacing the alkaline battery pack at the conclusion of its modest life cycle. These growing costs prompted one designer to look to primary lithium as a power source for these critical devices.
Lithium offers nearly triple the energy density at 900 Wh/L versus alkaline's 320 Wh/L. Electrochem's lithium chemistry can also deliver up to 3.9 V whereas alkaline can only provide 1.5V. Beyond this, lithium can deliver in a temperature range of -55°C to +200°C where alkaline's boundaries are a much more narrow range of -20°C to +54°C.
Working together, Electrochem and the marine engineers designed a custom pack to fit the tsunami system's specifications. The superior nature of the Electrochem cells allowed the buoy and ocean floor unit to receive the same amount of power from the primary lithium pack at less than half the volume of alkaline. In addition, it was obvious that longer deployment would mean less replacement costs and more continuous data collection. For a D size cell, alkaline will provide approximately 22.5 Watt hours where as primary lithium chemistry will deliver for 59 Watt hours.
The decision was made to create a custom lithium pack that would deliver more than twice the capacity of alkaline for the same volume that was previously in the device. The resulting lithium pack configurations consist of 16, 20, 24, and 48 cell combinations of DD size cells. These cells leverage Electrochem's spiral wound technology and enhanced bromine chloride chemistry to deliver up to 240 amp hours of power per pack to the system.
With a vital tsunami detection system such as this, the cost of device failure due to power loss can be as high as death. The engineers in California credit the Electrochem team with providing researchers with a power solution that fits all their needs. With this trusted power source in place, marine engineers can set their concerns aside and concentrate on advancing the science of early tsunami detection.
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