Gary J. Loeber

Lithium-ion testing for spacecraft applications

The Air Force Research Laboratory is developing lithium-ion batteries for low earth orbit (LEO) and geosynchronous earth orbit (GEO) spacecraft applications. As a part of this lithium-ion battery development effort, a testing program is underway to determine the viability of lithium-ion batteries for LEO/GEO applications. For LEO, lithium-ion battery cycle lifetimes of >60,000 cycles at 25% depth-of-discharge (DOD) are projected. For GEO, lifetimes of >14 years at 80% depth-of-discharge are projected.

Testing of Lithium-Ion 18650 Cells and Characterizing/Predicting Cell Performance

The performance of lithium-ion cells, as determined from in-house testing, is primarily a function of cell design/materials, charge/discharge rate, ambient temperature, and the number of charge/discharge cycles. Testing of lithium-ion 18650 cells was performed in order to characterize their behavior and to eventually predict the performance of lithium-ion cells of various sizes. AC impedance spectroscopy was used to determine the interfacial resistance of the lithium-ion cells as a function of temperature, state-of-charge, and cycle number. From these results, a nonisothermal mathematical model was developed and preliminary results are presented.

Aircraft Battery Design Concept for Improved Ultra Low Temperature Performance

Abstract : The AFRL, Electrochemistry and Thermal Sciences Branch has evaluated numerous aircraft battery designs and chemistries since the 1960s. Recent experiments on advanced battery chemistries have shown poor performance at ultra low temperatures below -20 deg C. Aircraft battery designs stress low weight and volume and maximum capacity. One design concept uses lower capacity cells in a series parallel configuration to reduce overall battery resistance and should also improve ultra low temperature performance. Our organization has begun experiments with series-parallel cell designs to evaluate the concept and to solve low temperature performance issues. Progress, observations on the effect of different chemistries, and the impact on aircraft battery characteristics are discussed.

Advances in Low Temperature Performance of Nickel-Metal Hydride Aircraft Batteries

The Air Force Research Laboratory (AFRL), Energy Storage and Thermal Sciences (PRPS) Branch has been developing nickel-metal hydride (Ni-MH) rechargeable batteries as an environmental replacement for existing valve regulated lead-acid (VRLA) and vented/sealed nickel-cadmium (VNC/SNC) batteries since 1995 and has evaluated cylindrical, prismatic and bipolar designs for this application. Recent advances in cell chemistry and design have resulted in a significant improvement in ultra low temperature performance indicating the suitability of these batteries for military aircraft applications over the temperature range from -40 °C to +65 °C. Results of the latest in-house tests of developments in bipolar and prismatic cell and battery designs indicate the current prismatic cell formulations are limited to temperatures above -25 °C while those used in bipolar designs operate over the full military aircraft temperature regime.

Nickel-metal hydride (Ni-MH) technology evaluation for aircraft battery applications

Available cylindrical and prismatic commercial Ni-MH batteries using AB/sub 5/ and AB/sub 2/ cathodes were evaluated for possible application to military aircraft batteries. Commercial AB/sub 5/ technology is further advanced than AB/sub 2/ technology and would require less alloy, electrolyte and single cell/battery development for near term (3-5 years) applications. Tested AB/sub 2/ technology appears inadequate to meet the near term military requirements and would require a major development in the alloy to overcome the irreversible capacity loss at temperatures above 49/spl deg/C. In addition, significant advances in alloy, electrolyte and single cell/battery development would also be needed.