Mining Contract: Battery Technology

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Contract #	200-2014-58752
Start Date	9/1/2014
End Date	1/21/2017
Research Concept	In an emergency situation in a mine, a communications and tracking system that uses battery power may be necessary for personnel to communicate with the mine operations center. For batteries used in these systems, end of battery life is presently determined by chronological age. Battery life is affected by the number of charging cycles, temperature, and the charging voltage. These parameters contribute to grid corrosion, sediment build-up, top lead corrosion, and sulfation, leading to premature and indeterminate end of life. Battery characterization overcharge and discharge cycles will provide a more accurate method of determining battery end of life.
Topic Area	Electrical Safety

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

The objective of this research is to develop technology that is broadly applicable to mobile and battery-driven equipment in hazardous environments. Off-the-shelf batteries do not include integrated current-limiting circuitry required by the Mine Safety and Health Administration (MSHA), or voltage, current, and temperature monitoring circuitry necessary to predict battery health. Every battery model needs its own characterization to predict its state of health because construction methods affect internal resistance, grid corrosion, and sulfation effects.

Innovative Wireless Technologies (IWT), Inc., has developed an intrinsically safe backup battery for use in its SENTINEL™/ACCOLADE™ communications and tracking system. This battery uses a series resistor and fuse to limit the current available at the battery terminals during charge and discharge cycles. The current-limiting components limit the input and output energy of the devices to meet MSHA ignition curve requirements. The current-limiting circuit components are selected to meet ratings and requirements of intrinsic safety criteria.

Under this contract, IWT will initially demonstrate and subsequently commercialize the viability of this technology through a highly reliable battery backup and charging system for the SENTINEL™/ACCOLADE™. The battery backup system will include an intrinsically safe Smart Battery control that monitors the battery during the charge and discharge cycles, a compatible battery charger for an intrinsically safe Smart Battery, and an algorithm for determining the Smart Battery’s health. The intrinsically safe Smart Battery includes a fuse and current-limiting series resistor (or equivalent active circuitry) to meet MSHA certification requirements. Off-the-shelf chargers do not compensate for the intrinsically safe circuitry and terminate the charging cycle before the battery is completely charged. To address this issue, IWT will design a custom charger that compensates for the intrinsically safe circuitry and allows a complete charging cycle. The custom charger will measure the battery voltage, current, and temperature during the charging cycle and adjust the charging current to prevent the possibility of thermal runaway.

The Smart Battery, Smart Battery Charger, and Smart Battery characterization concepts can be applied to all types of batteries employed in the mining environment. These capabilities can be applied in other scenarios/markets including rescue teams, first responders, and industries that employ toxic and explosive gases. By employing standard components and manufacturing processes, the battery technology design will support a fast transition to production.