1. ARL/Northeastern University Progress Report / Visit to ARL Brad Lehman (PI) Visiting Grad Students: Rosa Ciprian, Florent Boico, Jennifer Savage Dept. Elect. & Comp. Engin. Northeastern University Lehman@ece.neu.edu (617)373-3052 Tuesday May 31, 2005 Project 1: Field Sustainment Power Conditioning (Wes Tipton) Project 2: High Temperature DC/DC Converter (Damian Urciuoli)

2. ARL/Northeastern University Progress Report / Visit to ARL Have we aged since October 27, 2004?

3. Overview of Projects Field Sustainment Power Conditioning –Awarded Q4FY03 –NU approximately $80k/year Model, design and build solar battery chargers for NiMH batteries Test solar arrays and batteries ARL funding for 1 grad student, but usually 2-3 work on the project (student projects, matching internal funds, etc.): Florent Boico, Jennifer Savage, Dung Nguyen –Clark Atlanta University approximately $20k/year for simulation support High Temperature DC/DC Converters –Awarded Q4FY04 at approximately $190k/year Funded 2 students, but 3 grad students are actually working on project (matching funds): Rosa Ciprian, Ting Qian, Wei Song –Results to date include Prototype half-bridge: copper board prototype and pcb design for 2-stacked board design, 1/2 –brick size (on order) of 2.4” x 2.3”x ~1” Simulations in Spice: evaluations of various topologies Thermal simulations: CFD and simplified electro-thermal models Invention of new two-stage topology for high voltage applications

4. Technical Challenges: Problems reported by CERDEC of damaged batteries when charging with portable solar arrays; Basic research: charging batteries in (relatively) high temperature with changing power source has not been investigated before; Applied research: developing and building prototype chargers. Field Sustainment Power Conditioning Major Accomplishments: Team Members Brad Lehman (NEU), Khalil Shujaee (CAU), Wes Tipton, (ARL) Project Objective/Description 1.Explain reasons for: Reduced battery capacity, damaged batteries and reduced life-cycle; 2.Design, develop, and test solar battery charge controllers that: Fully charge batteries, maintain battery capacity and life- cycle.  Explained performance degradation of batteries when charging with solar array is due to high temperature overcharging ;  Designed, built, and tested solar array NiMH battery charger control algorithms; -- New temperature differential charge control algorithm developed in 2005; -- Max. Power Point Tracker for charger (2005); -- Preliminary patent disclosure (2005);  2005 IEEE PESC paper to appear in June. Note: 2005 Renewal funding received 5 months late: delayed research in solar charging of Li-ion batteries. Charger

5. Technical Challenges: High power density desired but… Large number transformer turns ratio 85 degree Celsius Year 1 with no air flow (increase to above 100 deg. Celsius in Y2) 3000V input-output isolation Primary switches are the source of heat/power loss Synchronous Rectification? High Temperature DC/DC Converter Some Year 1 Accomplishments: Damian Urciuoli Team Members: Brad Lehman, Northeastern University (NEU), Damian Urciuoli, (ARL) Project Objective/Description 1.Design a high power density converter with target size of ¼ brick (perhaps a little taller if place on two stacked boards) 2.Vin = 600 V; Vout = 28V, 1% load regulation 3.Year 1: Ambient temperature -10 o C ~85 o C  Simulations --- Spice analysis of candidate topologies: half- bridge, asymmetrical half bridge, invented topologies, … --- Thermal CFD and simplified steady state electro-thermal models  Prototype Half-bridge --- Open loop power efficiency above 89% --- Gerber files for ½ brick, two stacked board prototype have been shipped out for fabrication  Invented new two stage isolated DC-DC converter for high-voltage applications Primary Turns404752 Secondary Turns677 Vi(V)618623614 Ii(A)0.1780.1770.179 Vo(V)28 Io(A)3.53.506 Efficiency(%)89.189.089.3 Prototype half-bridge