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1 AFRL-PR-WP-TR FEASIBILITY ANALYSIS FOR AN ENVIRONMENTAL NICKEL-METAL HYDRIDE AIRCRAFT BATTERY 4M,.- m JOHNR.FENTER V ^ GRC INTERNATIONAL, INC MANUFACTURING OPERATIONS 2940 PRESIDENTIAL DRIVE, SUITE 390 FAIRBORN, OH AUGUST 2000 FINAL REPORT FOR PERIOD 07 AUGUST AUGUST 2000 Apprved fr public release; distributin unlimited PROPULSION DIRECTORATE AIR FORCE RESEARCH LABORATORY AIR FORCE MATERIEL COMMAND WRIGHT-PATTERSON AIR FORCE BASE, OH

2 NOTICE Using Gvernment drawings, specificatins, r ther data included in this dcument fr any purpse ther than Gvernment prcurement des nt in any way bligate the U.S. Gvernment. The fact that the Gvernment frmulated r supplied the drawings, specificatins, r ther data des nt license the hlder r any ther persn r crpratin; r cnvey any rights r permissin t manufacture, use, r sell any patented inventin that may relate t them. This reprt is releasable t the Natinal Technical Infrmatin Service (NTIS). At NTIS, it will be available t the general public, including freign natins. THIS TECHNICAL REPORT HAS BEEN REVIEWED AND IS AP- PROVED FOR PUBLICATION. A.Siu^c^ii^t^^ JOHN K. ERBACHER BRIAN G. HAGER Prject Scientist Chief, Energy Strage & Thfejbal Sciences Branch Pwer Divisin Pwer Divisin fc fryt- *' C&CQCXP L. ERNO, Lt. Clnel, USAF feputy Chief Pwer Divisin D nt return cpies f this reprt unless cntractual bligatins r ntice n a specific dcument requires its return.

3 REPORT DOCUMENTATION PAGE Frm Apprved OMB N Public reprting burden fr this cllectin f infrmatin is estimated t average 1 hur per respnse, including the time fr reviewing instructins, searching existing data surces, gathering and maintaining the data needed, and cmpleting and reviewing this cllectin f infrmatin. Send cmments regarding this burden estimate r any ther aspect f this cllectin f infrmatin, including suggestins fr reducing this burden t Washingtn Headquarters Services, Directrate fr Infrmatin Operatins and Reprts, 1215 Jeffersn Davis Highway, Suite 1204, Arlingtn, VA , and t the Office f Management and Budget, Paperwrk Reductin Prject ( ), Washingtn, DC AGENC Y USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED 4. TITLE AND SUBTITLE AUGUST 2000 FEASIBILITY ANALYSIS OF AN ENVIRONMENTAL NICKEL-METAL HYDRIDE AIRCRAFT BATTERY 6.AUTHOR(S) JOHN R. FENTER Final Reprt fr 08/07/ /15/ FUNDING NUMBERS C:F D-5101 PE: 69199F PR: OAFP TA: 97 WU: PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) GRC INTERNATIONAL, INC MANUFACTURING OPERATIONS 2940 PRESIDENTIAL DRIVE, SUITE 390 FAIRBORN, OH SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) PROPULSION DIRECTORATE AIR FORCE RESEARCH LABORATORY AIR FORCE MATERIEL COMMAND WRIGHT-PATTERSON AIR FORCE BASE, OH POC: DR. JOHN K. ERBACHER, AFRL/PRPB, (937) PERFORMING ORGANIZATION REPORT NUMBER 10. SPONSORING / MONITORING AGENCY REPORT NUMBER AFRL-PR-WP-TR SUPPLEMENTARY NOTES 12a. DISTRIBUTION / AVAILABILITY STATEMENT Apprved fr public release; distributin unlimited. 12b. DISTRIBUTION CODE 13. ABSTRACTfMflM»»» 200 Wrds) Nickel-Metal Hydride prismatic cells have been designed, fabricated, and characterized fr perfrmance acrss the temperature range f-40 C t + 70 C. The ptimized designs were validated in cntrlled labratry cnditins and under simulated envirnmental testing cnditins. All aspects f the cells were evaluated and selected ptimizatin was designed int the cells t advance the Ni-MH technlgies t attain the prgram target gals. Electrde frmulatins, prcesses, electrlyte percentages, separatr materials and thickness, and assembly were evaluated in specific cell design cnfiguratins. The charging prcedure and algrithms were determined and implemented. These test and evaluatin cnditins were recmmended fr repeatable charging and safety limits t independently cnfirm the perfrmance f the prttype designed battery. One prttype battery was delivered having apprximately 64 Wh/kg using cells with 43 Ah capacity at C/2. Amng the key perfrmance variables fr this next generatin battery are brad temperature range and minimal self-discharge. Bth key perfrmance variables were enhanced sufficiently t make the Ni-MH battery technlgy a strng alternative battery pwer surce in military flight vehicles. 14. SUBJECT TERMS Aircraft Battery, Nickel-Metal Hydride, Rechargeable Battery 15. NUMBER OF PAGES SECURITY CLASSIFICATION OF REPORT Unclassified 18. SECURITY CLASSIFICATION OF THIS PAGE Unclassified 19. SECURITY CLASSIFICATION OF ABSTRACT Unclassified 16. PRICE CODE 20. LIMITATION OF ABSTRACT SAR NSN Standard Frm 298 (Rev. 2-89) Prescribed by ANS[ Std. Z

4 TABLE OF CONTENTS Sectin Page 1.0 Intrductin Design Studies Technical Directin SAFT - Prismatic EEI- Biplar Materials Electrdes Separatrs Electrlytes Early Cell Designs SAFT America - Prismatic Cell Design Electr Energy, Inc. (EEI) - Biplar Cell Design Interim Testing Cnclusins Characterizatin and Testing Methds Cell Capacity Discharge Perfrmance Charge Perfrmance Self-Discharge Ambient Life Cycle Tests Integrated Envirnmental Cyclic Tests Test Set Pre-Prttype Battery Assembly Summary References 26

5 LIST OF FIGURES Figure Page 1 Explded View f a NIMH Cell Shwing Assembly Detail 4 2 Biplar Cell Schematic 4 3 Cell Capacity vs Discharge Temperature fr a C/2 Rate f Discharge 10 4 Cell Vltage at 50% Depth f Discharge vs Discharge Temperature fr a C/2 Rate f Discharge 11 5 Cell Capacity vs Discharge Temperature fr a 1C Rate f Discharge 11 6 Cell Vltage at 50% Depth f Discharge vs Discharge Temperature fr a 1C Rate f Discharge 12 7 Cell Capacity vs Discharge Temperature fr a 2C Rate f Discharge 12 8 Cell Vltage at 50% Depth f Discharge vs Discharge Temperature fr a 2C Rate f Discharge 13 9 Discharge Capacity vs Cell Charge Temperature fr C/2 Rate f Charge Discharge Capacity vs Cell Charge Temperature fr 1C Rate f Charge End f Charge Cell Vltage vs Charge Temperature fr 1C Rate f Charge Discharge Capacity vs Cell Charge Temperature fr 2C Rate f Charge End f Charge Cell Vltage vs Charge Temperature fr 2C Rate f Charge Self-discharge Over 7 Days vs Test Temperature fr all Fur Cell Designs Capacity Check Every 50 Cycles Measured by Cell Capacity vs Cycle Number fr Each Cell Design Cell Vltage at 50% Depth f Discharge During the Cell Capacity Check fr each Cell Design Test Scheme fr Flight System Prfile (fr Vented Ni-Cd Battery Charger Perfrmance) Bttm Curve: Cell Vltage after Discharge Cycle at Crrespnding Temperature. Tp Curve: End f Charge Cell Vltage Prir t Next Cycle at Crrespnding Temperature Cell Capacity Check at +23 C after Designated Cycle Number Test Set f Fur Ni-MH Prismatic Cells Frm SAFT Layut and Intercnnectins f the 20 Cells in the Pre-Prttype Battery Fully Assembled and Sealed Ni-MH Pre-Prttype Battery With Cnnectr 24

6 LIST OF TABLES Table Page 1 SAFT NIMH Battery Parameter Values Achieved ix 2 Envirnmental Ni-MH Battery Perfrmance Parameters 1 3 Cncept Studies Subcntractrs 2 4 Cell Capacity Measurements(after cell frmatin) 9 5 Descriptins f Test Cnditins fr Flight System Prfile with Reference t Figure 17 (Aircraft Battery System, Spec #16ZE3743B, 18 June 1993) 21 6 SAFT Ni-MH Battery Parameter Values Achieved 25

7 FOREWORD The Air Frce Strategic Envirnmental R&D prgram supprted this effrt t demnstrate an envirnmentally safe alternative frm, fit, and functin battery fr the F- 16 Pre-Blck 40 main aircraft battery. The technical perfrmance target was t achieve a specific energy density f 75Wh/kg fr the Mre Electric Aircraft Generatin II prgram. The prject was cntracted under the Advanced Manufacturing Technlgy Feasibility Demnstratins, cntract F D-5101, in the Materials and Manufacturing Technlgy Directrate, Air Frce Research Labratry. Dr. Jhn K. Erbacher, Air Frce Research Labratry, Prpulsin Directrate, Battery Technlgy Branch prvided technical guidance. Mr. Timthy Prvens, Aernautical Systems Center, Envirnmental, Safety, and Health Pllutin Preventin Branch prvided funding fr the three-year effrt. Nickel-Metal Hydride (Ni-MH) prismatic cells have been designed, fabricated, and characterized fr perfrmance acrss the temperature range f -40 C t +70 C. The ptimized designs were validated in cntrlled labratry cnditins and under simulated envirnmental testing cnditins. All aspects f the cells were evaluated and selected ptimizatin was designed int the cells t advance the Ni-MH technlgies t attain the prgram target gals. Electrde frmulatins, prcesses, electrlyte percentages, separatr materials and thickness, and assembly were evaluated in specific cell design cnfiguratins. The charging prcedure and algrithms were determined and implemented. These test and evaluatin cnditins were recmmended fr K- peatable charging and safety limits t independently cnfirm the perfrmance f the prttype designed battery. Amng the key perfrmance variables fr this next generatin battery are brad perating temperature range and minimal self-discharge. Bth key perfrmance variables were enhanced sufficiently t make the Ni-MH battery technlgy a strng alternative t cnventinal battery pwer surces in military flight vehicles. Nickel-Metal Hydride battery technlgy is a technically cmpatible and envirnmentally imprved alternative t existing nickel-cadmium and sealed lead-acid batteries in many Air Frce system applicatins.

8 ACKNOWLEDGMENTS The wrk perfrmed under Cntract F D-5101, Delivery Order 23, was supprted by the Prpulsin Directrate f the Air Frce Research Labratry and funded by the USAF Strategic Envirnmental Research, Develpment, and Pllutin Preventin prgrams, Aernautical Systems Center, Wright-Pattersn AFB, Ohi. Mr. Timthy Prvens frm the Aernautical Systems Center, ASC/ENVV, prvided funding fr the effrt. Dr. Jhn K. Erbacher f AFRL/PRPB, as the Air Frce prject manager, prvided technical supprt and guidance. Mr. Jhn R. Fenter f GRC Internatinal, Inc. was prject manager; and Mr. Bryan C. Mazey f GRC Internatinal, Inc. prvided technical assistance.

9 EXECUTIVE SUMMARY Fr military airbrne and grund applicatins, the mainstay in rechargeable batteries has been the vented nickel-cadmium (Ni-Cd) battery. Unfrtunately, due t the heavy maintenance and upkeep requirements, use f these batteries is csting the Air Frce an estimated $50 millin per year. In additin, these batteries, and pssible lead-acid alternatives, use hazardus materials targeted n the EPA 17 list fr eliminatin frm use in the US. The Secretary f the Air Frce supprts the minimizatin and/r eliminatin f these materials in the SAF/AQ Acquisitin Plicy Memrandum 94A-003, 23 Aug Currently, there are n envirnmentally acceptable alternative batteries that meet EPA requirements, cmply with the HQ USAF plicy and meet user perfrmance requirements. Recently, AFRL/PRPB funded Small Business Innvative Research (SBIR), in-huse, and ther research effrts t develp nickel-metal hydride (NiMH), lithium-in and lithium plymer batteries as ptential envirnmentally acceptable aircraft battery systems. Availability f cmmercial NIMH batteries, the envirnmental alternative t the Ni-Cd battery, prmpted AFRL/PRPB t evaluate the capability f Ni-MH batteries t meet military aircraft requirements. This test prgram defined shrtcmings f cmmercial Ni-MH batteries and areas f develpment needed fr applicatin t the Mre Electric Aircraft (MEA) and/r as a pssible alternative t existing aircraft Ni-Cd and lead-acid batteries. The cmmercial batteries that were tested did nt meet the military perating upper temperature range, charge/discharge capacity and high self-discharge requirements. This feasibility prject addressed the limitatins f the cmmercial metal hydride batteries and cnducted perfrmance demnstratins leading tward the insertin f metal hydride technlgy as an imprved envirnmental alternative using the F-16 Pre-Blck 40 Main Aircraft Battery (MAB) as the baseline cnfiguratin. The prject identified and analyzed a number f design cncepts. The GRCI team, Electr Energy, Inc., Eagle-Picher Technlgies, Inc., SAFT America, Inc., and Yardney Technical Prducts as subcntractrs, assessed imprvements t the F-16 MAB design using bth biplar and prismatic baseline battery cncepts. Based n the mdified designs, material studies t validate the design changes were identified. Tw cntractrs, Electr Energy, Inc. fr biplar designs and SAFT America fr prismatic designs, were selected t cnduct material studies and validate their designs. The materials studies were cnducted t cnfirm the baseline cell and battery designs fr bth the biplar and prismatic cncepts and frmulate a test plan fr single cell and battery tests fr perfrmance cmparisns. Multiple metal hydride allys, electrlytes and nickel electrde frmulatins were selected and tested t ascertain cell capacity and temperature limitatins and t determine the ptimum electrchemical cnfiguratins t maximize single cell perfrmance. Characterizatin f individual cells and analysis f the test results shwed the perfrmance f bth the biplar and the prismatic cncepts were prmising. Bth Electr Energy, Inc. and SAFT America were selected fr further scale up and design imprvements. By pursuing tw different design cncepts, Electr Energy, Inc. n the biplar cncept and SAFT America n the prismatic cncept, the technical risk fr success was cnsiderably lwer. Hwever, nly ne design cncept was planned t be selected fr design ptimizatin

10 and integratin int a battery cnfiguratin after cmpletin f cmparative testing and evaluatin. New materials and cmbinatins were evaluated fr the psitive Ni electrde, the negative metal hydride electrde, and the separatr. The electrlyte was mdified where apprpriate. The cell size was scaled up frm labratry test samples t a size needed fr battery integratin. The test plans and cnditins were specified t allw cmparisn between the technlgies and the designs. A cmmn test matrix fr bth cell cncepts was defined fr cell capacity measurements, ambient life cycle, and envirnmental life cycle measurements. A number f cell designs were evaluated under life cycle testing, charging and discharge perfrmance versus temperature, and charge retentin r self-discharge ver 7 days versus temperature. Sample cells f each ptimum cell cncept were delivered fr perfrmance verificatin testing. With the assistance f a Technical Advisry Cmmittee, SAFT America was selected t cntinue based n cell perfrmance and reduced technical risk fr battery assembly and integratin. Using the final design f the best cell at this juncture, a number f first article test sets cmpsed f fur cells were delivered fr test. A detailed test plan, test prcedures, and characterizatin f the test sets prvided data fr analysis leading t the battery design. The characterizatin data verified the earlier design predictins, develped perfrmance data fr charging and discharging against temperature and fr self-discharge perfrmance. The characterizatin data and test prcedures frmed the basis t define a test plan. The test plan f fur cells fr labratry testing crrelated as much as pssible t the F-16 battery lad prfile r t knwn critical use cnditins. All final design changes were incrprated int the pre-prttype, baseline, nickel-metal hydride battery. Charge mnitring guidance fr the pre-prttype baseline battery was determined fr safety and handling. One preprttype battery with a test plan was delivered fr verificatin f perfrmance parameters shwn in Table 1. Table 1 SAFTNi-MHBattery Parameter Values Achieved Nminal Vltage (V) 24 Rated Capacity (Ah) 43 Current (A) 48 Operating Temperature Range ( C) Typical Battery Energy at C/2 (Wh) 1,126 Typical Specific Energy Density (Wh/kg) 64 Typical Vlumetric Energy Density (Wh/I) 127 Ttal Battery Weight (kg {lb}) 17.7 {39} Maintenance Interval Self-Discharge (<25% ver 7 days) -40 t +71 (with heaters) Maintenance Free 25%frT<40 C

11 1.0 INTRODUCTION Nickel-MetalHydride battery technlgy is a technically cmpatible and envirnmentally imprved alternative t existing nickel- cadmium and sealed lead-acid batteries in many Air Frce system applicatins. One particularly viable alternate technlgy t the Ni-Cd and Pbacid batteries is Nickel-MetalHydride (Ni-MH). Ni-MH batteries are under evaluatin fr ptential applicatin as a replacement pwer surce fr the existing Ni-Cd and Pb-Acid batteries currently used by the USAF. Besides being envirnmentally friendly and psing n threat in the event f peratr expsure, advantages f metalhydride batteries ver the presently used Ni-Cd and Pb-acid technlgies include; higher efficiency per unit vlume, higher energy density, lwer peridic maintenance requirements, and higher specific pwer utput. This Air Frce spnsred prject with GRC Internatinal was t develp and demnstrate a sealed, maintenance free, vlt, Ni-MH aircraft battery that meets the fllwing K- quirements: An envirnmentally safe alternative frm, fit, and functin battery fr the F-16 C/D Pre-Blck 40 main aircraft battery in accrdance with the existing battery perfrmance specificatin, A desired energy density f 75 Wh/kg fr the Mre Electric Aircraft. The Air Frce Research Labratry and the Air Frce Strategic Envirnmental R&D prgram supprted this effrt with the target perfrmance parameters fr a final battery as listed in Table 2. Table 2 Envirnmental Ni-MH Battery Perfrmance Parameters Nminal Vltage (V) 28 Capacity (Ah) 50 End f Life Capacity (Ah) 18 (Maintained at 14.5) Current (A) 48 (Maximum) Operating Temperature Range ( C) r -40 t +71 Battery Energy at C/2 (Wh) I,32~5 Specific Energy Density (Wh/kg) 75 Vlumetric Energy Density (Wh/1) 177 Ttal Battery Weight (kg {lb}) 18.18(40} Mean Time Between Failures (MTBF) >6000 h Maintenance Interval Maintenance Free fr Three Years Self-Discharge (<25% ver 7 days) All Operating Temperatures

12 2.0 DESIGN STUDIES The develpmental nature f this prject required a brad assessment f industry activities and state-f-the-art Ni-MH batteries. In rder t btain an assessment f different designs, materials, and fabricatin experience, an early study and analysis was cnducted t define the benefits and limitatins f differing appraches and t determine the cmpanies having the strngest technical grup t bring the technical advances tgether int a military aircraft applicatin. A slicitatin fr a design and cnceptual study was initiated with fur cmpanies listed in Table 3. Table 3 Cncept Studies Subcntractrs Yardney Technical Prducts, Inc. Pawcatuck, CT (860) Eagle-Picher Industries, Inc. (EPI) Jplin, MO (417) Electr Energy, Inc. (EEI) Danbury, CT (203) SAFT America, Inc. Cckeysville, MD (410) The gals and verall prgram bjectives were presented t each f the fur cmpanies. Althugh all fur cmpanies cncluded that Ni-MH culd cnceivably supply the high energy and pwer applicatins demanded by the F-16 aircraft battery, their specific apprach, design, and material cmpsitin required t fulfill this bjective differed greatly. A Technical Advisry Cmmittee (TAC) was established t advise GRCI and the prgram managers as a means t evaluate the wrk prpsed by each f the subcntractrs. At the cnclusin f Cncept Studies, the TAC cnferred fr a frmal surce selectin review and evaluated the technical presentatin materials frm each f the subcntractrs. The surce selectin prcess evaluated the capabilities f the subcntractrs using the fllwing factrs t determine technical merit and likelihd f successfully cmpleting the effrt. 1. Technical Aspects; Cell design, battery design material studies, single cell studies, baseline battery studies, and prttype MHAB. 2. Merit f Technical Apprach; These factrs included infrmatin such as previus studies, findings, data results f battery, single cell and material research alng with current avenues f chemical and battery technlgy being explred. 3. Specific Aspects f Metal Hydride Battery and Cell Operatin; Cathde, ande, electrlyte, case materials, lad prfiles, pwer requirements, charger interface, and perfrmance-ver-temperature range. 4. Risk Mitigatin Strategies; Such as alternative appraches and materials. 5. Planning Requirements; Schedule by phase and task alng with manhur allcatin, materials estimate, and travel requirements.

13 6. Prgram Management Factrs; Overall prgram rganizatin, ptential risk areas t be addressed, expected future utcme and the ptential effects n schedule, success, and delivery. 7. Other/Additinal Factrs; Cst share (if any), amunt and type f cst share, and supplemental wrk prpsed, if any. Based n the surce selectin cmmittee's scring results and subsequent discussin and review f all materials, the TAC was unanimus in their decisin that Electr-Energy Inc. and SAFT America prvided the strngest technical appraches while simultaneusly giving the prject reduced technical risk with tw design alternatives.

14 3.0 TECHNICAL DIRECTION The tw design types were chsen t cver alternative designs and material pssibilities and als prvided tw technical appraches fr military applicatins. One was a cnventinal cell design by SAFT America called prismatic having flat rectangular electrdes and separatrs that give a cmpact design with flexibility fr assembly int batteries meeting differing perfrmance requirements. A secnd design by Electr Energy is called biplar. The biplar cncept fr Ni-MH batteries are cells stacked tgether withut intercnnecting terminals in a cmpact arrangement. Bth cncepts were cnsidered technically sund and capable f maturing tward the prductin f envirnmental friendly, rechargeable, aircraft batteries. 3.1 SAFT - PRISMATIC The SAFT design was a cnventinal battery design called prismatic having flat rectangular electrdes and separatrs that give a cmpact design with flexibility fr assembly int batteries meeting differing perfrmance requirements (Figure 1). 3.2 EEI - BIPOLAR The Electr Energy design is called biplar. The biplar cncept fr Ni-MH batteries has been described in a number f patents ver the last few years. Biplar cells are stacked tgether withut intercnnecting terminals which prvide higher energy density and ptentially lwer cst than the cnventinal designs (Figure 2). 3.3 MATERIALS I«) Psitive Cntact Face Psitive Electrde.^y^ Separatr Negative Electrde Insulating Brder Seal Figure 2 Biplar Cell Schematic Figure 1 Explded View f a Ni-MH Cell Shwing Assembly Detail The metal hydride material cnstitutes the negative electrde. The metal hydride f chice fr this prject is the class f intermetallics knwn as AB5 where A is a strng hydride frming cmpnent and B is a weak hydride frmer. The A cmpnent is lanthanum r a less expensive ally f the lanthanide series called mischmetal: an unrefined mixture f rare earth metals including lanthanum, cerium, prasedymium, and nedymium. Cmpsitins f mischmetal depend

15 n the surce f the re and are nt expected t be identical between batches. The B cmpnent is nickel r an ally f nickel and the transitin metals, cbalt, manganese, and aluminum. These metals frm an AB 5 ally that absrbs hydrgen. Cerium imprves the crrsin resistance f the metal hydride and reduces the capacity decay when cycling. Cbalt imprves the high temperature delivered capacity f the psitive electrde. Thin electrdes give enhanced perfrmance fr lw temperature delivered capacity. Lw temperature perfrmance is impacted by the particular metal hydride ally used which cntrls the transprt f hydrgen in the lattice Electrdes The electrdes were cmpsed f a cnductive netwrk that was prcessed with a slurry f either psitive electrde material, Ni(OH)2, r the negative electrde material, the lanthanum-rich mischmetal hydride cmpsitin f rare-earth transitin metal hydrides. The strips cntaining the slurry are dried and laminated t a specified thickness. The thickness and weight f active material in the electrdes are critical t perfrmance as are the relative number f negative t psitive electrdes Separatrs Separatr materials were purchased frm different surces. The materials hld the electrlyte but are inert t the electrchemical activity f the cell. The thickness and weight are critical t the perfrmance f the cell Electrlytes The electrlytes were based n KOH.

16 4.0 EARLY CELL DESIGNS After 18 mnths int the effrt, the results f the tw subcntractrs were reviewed and evaluated. Supprt frm the TAC prvided additinal expert pinin and insight int the perfrmance demnstrated t date and the prjectins fr further advancement by each subcntractr. The fllwing paragraphs summarize the early cell design results f SAFT America and Electr Energy. 4.1 SAFT AMERICA - PRISMATIC CELL D ESIGN SAFT evaluated many materials and defined several prismatic cell designs that satisfied all the perfrmance requirements. The characterizatin data f cell charge and discharge capacity versus temperature, ambient cyclic testing at 50% depth f discharge, integrated envirnmental cyclic testing as simulatin f aircraft use cnditins, and self-discharge perfrmance, was very gd. The discharge perfrmance fr three ut f the fur design grups varied 7.7% frm the nminal capacity fr the 0.5C, 1C, and 2C discharge rates between -20 C and +50 C. The charge perfrmance f all fur grups varied 3.7% frm the nminal capacity at charge rates f 0.5C, 1C, and 2C in the temperature range between -20 C and +23 C. Analysis f the test data led SAFT t select and prpse ne cell design t satisfy the perfrmance requirements. The full perfrmance range was prjected t be achieved in the battery by using a heater blanket fr the lw temperatures and building in excess battery capacity fr the higher military temperature range. Bth f these engineering design methds were acceptable. 4.2 ELECTRO ENERGY, INC. (EEI) - BIPOLAR CELL D ESIGN The EEI cell data were questinable due t incnsistent results frm a sealed test fixture fr the larger 7x10 inch biplar cells, questinable test methds indicated by the similarity f test results fr different designed cells being tested tgether, and the significantly incnsistent test results amng cell sets with identical designs and fabricatin methds. 4.3 INTERIM TESTING CONCLUSIONS The effrt n the Ni-MH battery technlgy was intended t advance nly ne cncept f a cell and battery design, either prismatic r biplar. Bth battery designs had advantages: the prismatic design was mre mature but the biplar design affrded mre efficient packaging pssibilities. Althugh the prject was initiated with the strategy t select ne surce fr the effrt, when tw strng and viable cncepts were prpsed, the Air Frce decided t supprt bth t reduce the technical develpment risk. Hwever, as the prject prceeded, the need t select ne design fr further supprt and advancement became necessary because f funding limitatins. The effrt with SAFT America was cntinued. One prismatic cell design was selected and slight design changes were made based n the prir perfrmance data t give fur design alternatives. The data presented in the remainder f this reprt are limited t these fur designs frm SAFT America, called Serials, n the data graphs.

17 5.0 CHARACTERIZATION AND TESTING METHODS Each subcntractr prtected the technlgy and designs f the cells, materials, and manufacturing prcesses as prprietary. As a result, in the early phases f the prject, the test methds and cnditins were cnducted differently by each subcntractr. These issues caused the data generated by each subcntractr n the different designs t be nt cmparable. Specific test cnditins were discussed and identical test cnditins were defined fr each cntractr that wuld prvide perfrmance data useful fr direct cmparisn. Hwever, sme minr schedule slips and test fixture design differences resulted in sme areas nt being ne-t-ne cmparable but still reasnably similar. The data that were lacking r incmplete were nt critical t any pririty design determinatins nr prgrammatic decisins. Specific test cnditins were defined fr charge and discharge capacity versus temperature, self-discharge ver seven days, and ambient cyclic testing at 50% depth f discharge. The test schema and cnditins are included with the data charts in sectin 5.0. A simulatin f the flight checkut and engine starting cnditins was cnducted fllwing the Integrated Envirnmental Cyclic Test frm Lckheed Martin fr the F-16. Exceptins t the cnditins were taken t reflect expected use cnditins and the fact that a cell rather than a prductin battery was being characterized. 5.1 CELL CAPACITY The measurement f the capacity f the cell indicates the energy cntent available and an verall prjectin f perfrmance. The biplar and prismatic cell design alternatives early in the prject were measured by the manufacturing cmpany using their defined cell frmatin and test cnditins. In rder fr GRCI t cmpare perfrmance between the designs, a specific test plan was develped. Each manufacturing cmpany reviewed and agreed t prvide data in accrdance with the matrix shwn in Table 4. The upper and lwer test temperature range fr the discharge perfrmance are a +70 C high temperature test and a -30 C lw temperature test. The -30 C test data were required but the +70 C was necessary nly if needed t assist the discriminatin between cells at the higher temperatures. Likewise, discharge perfrmance at - 40 C was measured if data at the higher temperatures were nt discriminatry. After frmatin, the cell capacity measurement prcess cycle fr the SAFT cells was defined as fllws: Discharge Rate vs Temperature Charge at 2 hurs at C/2 + 3hurs at C/20 at +23 C Rest 5 hurs at the test temperature Discharge at the specified rate t 0.9V/cell Rest until reaching +23 C

18 Charge Rate vs Temperature Rest 5 hurs at the test temperature Charge at the specified time and rate Rest 5 hurs in rder t achieve +23 C Discharge at C/2 t 0.9V/cell As part f the cyclic test prcess, any residual charge in the cell was discharged at +23 C. Als, after each temperature test, a cell capacity check cycle was perfrmed as fllws: Capacity Check Cycle at +23 C Charge 2 hurs at C/2 + 3 hurs at C/20 Rest 15 minutes Discharge at C/2 t 0.9V/cell Rest in rder t achieve +23 C The charging prcess and charge mnitring studies perfrmed later in the prgram prvided specific charging algrithms fr the test cells and batteries. Therefre, fr the capacity measurements cnducted later, the revised charging prcess determined fr the test sets and batteries was used, as apprpriate.

19 Table 4 Cell Capacity Measurements (after cell frmatin) DISCHARGE PERFORMANCE Standard Charge: Ambient Discharge Temperature -30 C -20 C 0 C Ambient +50 C +70 C Cell Capacity, Ah Discharge Rates t 0.9v/cell C/2 C 2C CHARGE PERFORMANCE Charge Temperature Charge Rate Cell Capacity, Ah (Standard Discharge: RT t 0.9v/cell) -20 C C/2 C 2C 0 C C/2 C 2C Ambient C/2 C 2C +50 C C/2 C 2C

20 The material cmbinatins and cell designs narrwed dwn as the prject prceeded. The best perfrmance was prjected frm fur specific cmbinatins f materials, designs, and prcesses. These fur designs were cnsidered mst prmising t satisfy the prgram bjectives and were labeled as: T3 - Serial 1 T3 - Serial 2 T3 - Serial 3 T3 - Serial 4 Fr each design a number f identical cells were fabricated. The cells then were put in either Grup 1 fr the cell capacity and self-discharge testing, r in Grup 2 fr the life cycle testing Discharge Perfrmance Fr each cell design, a set f six identical cells were fabricated frm which the cell capacity measurements were taken as described abve. The perfrmance f the cell designs under cnditins f discharging and charging ver the temperature ranges f interest were measured. Fr discharge perfrmance, Figures 3 t 8 give the cell capacity average and the cell vltage at 50% depth f discharge at each temperature. Figure 3 shws the excellent discharge perfrmance frm -30 C t +70 C fr all fur-cell designs. As the discharge rate increases frm C/2 t 2C, the cell capacity is cnsistently high at 40Ah fr three designs at - 20 C but drps t 30 Ah at +70 C at the 2C rate f discharge as shwn in Figure 7. The maximum cell capacity at each discharge rate remains at nminally Ah at 23 C. Perfrmance Single Cell Test C/2 rate discharge: cell capacity 50 _ Q. re O T3-Serial Discharge Temperature ( C) 70 Figure 3 Cell Capacity vs Discharge Temperature fr a C/2 Rate f Discharge 10

21 Single Cell Test: grup 1 cells C/2 rate discharge: cell vltage at 50% f DD Q Q w 105 Ö > 0.95 Test cnditins: -Charge 2 C/2 + C/20 at C -Rest 5 hurs at test temperature, -Discharge at C/2 rate t 0.9 V/cell T3-Serial 1 " T3-Serial 3 I I T3-Serial2 - T3-Serial Discharge Temperature ( C) Figure 4 Cell Vltage at 50% Depth f Discharge vs Discharge Temperature fr a C/2 Rate f Discharge Single Cell Test: grup 1 cells 1C rate discharge: cell capacity 45- _ 40 :.c < a 35^ < fe 30: i *; Q. 20 < O = 15-0) O 10: 5- i r 1 i i i Test cne itins: -Charge 2 C/2 + C/20 at C -Rest 5 hurs at test temperature, -Discha rge at 1C rate t 0.9 V/cell I!! I I I - -T3-Serial 1 T3-Serial 2 -*-T3-Serial 3-0-T3-Serial 4 ^^* > " u Discharge Temperature ( C) Figure 5 Cell Capacity vs Discharge Temperature fr a 1C Rate f Discharge 11

22 Single Cell Test: grup 1 cells 1C rate discharge: cell vltage at 50% f DD > D a O g Ü r CD O) S > ' V-A ' t ^ ^ g-sss ^ ^ Test cnditins " -Charge 2 C/2 + C/20 at +23*C -Rest 5 hurs at test temperature, -Discharge at 1C rate t 0.9 V/cell III! -*-T3-Serial1 T3-Serial 2 -*- T3-Serial 3-0- T3-Serial 4 III!! S Discharge Temperature ( C) Figure 6 Cell Vltage at 50% Depth f Discharge vs Discharge Temperature fr a 1C Rate f Discharge 50 Single Cell Test: grup 1 cells 2C rate discharge: cell capacity < d> 35 Ö) m <i> 30 > < >> 25 * * (0 Q. 20 r O a * -Charg 3 2 C/2 ^ 0/20 at +23 C -Rest 5 hurs at tes temperature, 1 1! - -T3-Serial 1 T3-Serial 2 -*- T3-Serial 3-0- T3-Serial 4 ^^"^ I! I I I i Discharge Temperature ( C) Figure 7 Cell Capacity vs Discharge Temperature fr a 2C Rate f Discharge 12

23 Single Cell Test: grup 1 cells 2C rate discharge: cell vltage at 50% f DD 1.25; > Q 1.20 : Q O 1.15 :! 1.10^ a> O) ra Ö > =S 1-00; Test cnditins: -Charge 2 C/2 + C/20 at +23 C -Rest 5 hurs at test temperature, -Discharge at 2C rate t 0.9 V/cell s k. t> ^ 3 T3-Serial 1 T3-Serial ; *-T3-Serial 3-0-T3-Serial 4 I I I I I Discharge Temperature ( C) Figure 8 Cell Vltage at 50% Depth f Discharge vs Discharge Temperature fr a 2C Rate f Discharge Charge Perfrmance Fr each cell design, the same set f six identical cells that were fabricated and used in the discharge capacity tests were used fr the charged capacity tests. Hwever, during the series f discharge tests, tw cells f the T3-Serial 3 design were damaged and were nt available fr charge perfrmance testing. Fr charge perfrmance, Figures 9 t 13 give the discharged cell capacity average and the end f charge cell vltage at each temperature. Figures 9, 10, and 12 have similar characteristics shwing stable charging perfrmance ver the lwer temperature range up t +23 C and drpping in charge perfrmance at +50 C with mre dispersin at the 2C rate f charge. The end f charge cell vltage, Figures 11 and 13, is similar fr bth the 1C and 2C rate f charge drpping frm 1.65 vlts at -20 C t 1.45 vlts at +50 C. 13

24 I 45 _ 40 : t 3 5 : 1 30 \ a. (0 " 25: T3 S) E> 20 : (0 1 15: Test cnditins: -Rest 5 hurs at Test Temperature 10 -Charge 0.5C -Rest 5 hurs at 23 C, 5: -Discharge at 0.5C rate t 0.9 V/cell Single Cell Test: grup 1 cells 0.5C rate Charge: Discharged Capacity H^ *^ ^5^N«^ L -*-T3-Serial 1 T3-Serial 2 -*-T3-Serial 3 - -T3-Serial 4 I I I I I I I I I I Charge Temperature ( C) Figure 9 Discharge Capacity vs Cell Charge Temperature fr C/2 Rate f Charge Single Cell Test: grup 1 cells 1C rate Charge: Discharged Capacity 45 : _ 40 : t 35 ^ 1 30 a ra " 25: T3 IB E> 20: (0 1 is i 5 10 : Test c ditins: -Rest 5 hurs at Te st Tempera tu re -Char e1h@1c -Rest 5 hurs at 23 c, -Disci" arge at 0.5C rate t 0.9 tfcell 5 : -^ r^w \ ^ > j i ~T3-Serial 1 T3-Serial 2 *~T3-Serial 3 "O T3-Serial 4 0 ^ I I I I I I Charge Temperature ( C) Figure 10 Discharge Capacity vs Cell Charge Temperature fr 1C Rate f Charge 14

25 Single Cell Test: grup 1 cells 1C rate charge: End f Charge Cell Vltage 1.70: 1.65: u 1.60: > ( : > «1.45: E? 1.40: ( : : UJ 1.25: Test cndit ns: -Rest 5 h urs at Test Te nperature -Charge 1h@ 1C -Rest 5 h urs at 23 C, -Discharc e at 0.5C rate t 0.9 V/cell I I I I I./U I I -4-T3-SeriaS 1 T3-Serial2 -A- T3-SeriaS 3 - -T3-Serial Charge Temperature ( C) Figure 11 End f Charge Cell Vltage vs Charge Temperature fr 1C Rate f Charge Single Cell Test: grup 1 cells 2C rate Charge: Discharged Capacity < 'Ü a r O u 0) O) r si u ut a 40 : 35 : <L J- " : 20: 15 : Test cnditins: -Rest 5 hurs at Test Temperature 10 : -Charge 2C _ T3-Seria! 1 T3-Seria! 2 -Rest 5 hurs at 23 C, 5 : -Discharge at 0.5C rate t 0.9 V/cell -*-T3-Serial 3-0-T3-Serial 4 0 ^ j. ß i 20 i 30 i 40 i 50 i Charge Temperature ( C) Figure 12 Discharge Capacity vs Cell Charge Temperature fr 2C Rate f Charge 15

26 Single Cell Test: grup 1 cells 2C rate charge: End f Charge Cell Vltage J, G > a O T Ü Test cndit ns: -Rest 5 h 3urs at Test Te nperature -Charge 0 5h@2C -Rest 5 h surs at 23 C, -Discharc e at 0.5C rate t V/ell - - T3-Serial 1 T3-Serial 2 -A- T3-Serial 3 -O T3-Serial 4 I 1 1 1, III! T 1, 1, 1, 1, Charge Temperature ( C) Figure 13 End f Charge Cell Vltage vs Charge Temperature fr 2C Rate f Charge 5.2 SELF-DISCHARGE Self-discharge perfrmance was measured n all fur-cell cnfiguratins ver the temperature range f-10 t +50 C. The test arrangement was t fully charge the cells, expse the pen circuit cells t the temperature f interest fr seven days, and then measure the residual capacity. Determinatin f self-discharge perfrmance required the fllwing: Determinatin f the initial capacity, Q, at +23 C: Charge the cell fr 2 hurs at C/2 + 3 hurs at C/20 Rest 15 minutes Discharge at C/2 t the cut-ff f 0.9V/cell Determinatin f the residual capacity, C r, after 7 days at the test temperature : Charge 2 hurs at C/2 + 3 hurs at C/20 at +23 C Open the circuit Age fr 7 days at the test temperature, -10, 0, +23, +50 C Rest in rder t achieve +23 C Discharge at C/2 t the cut-ff f 0.9V/cell at +23 C Calculatin f self-discharge percentage: Self-discharge % after 7 days = (Q_- C L ) x 100 Ci Figure 14 is the self-discharge percentage versus temperature. The graph shws all designs satisfy a self-discharge percentage belw 10% after 7 days at +23 C. Hwever, nly ne design has a self-discharge percentage belw 25% after 7 days at +50 C. 16

27 Single Cell Test grup 1 cells SeMscharge Perfrmance vs Temperature Test re a O) re requrepiert t 10 2D Test Temperature ( C) =F= 60 =F= Figure 14 Self-discharge Over 7 Days vs Test Temperature fr all Fur Cell Designs 5.3 AMBIENT LIFE CYCLE TESTS A crrelatin f cell and battery perfrmance t system requirements was required by the prject. Life cycle tests are cnsidered t be a labratry simulatin r expsure t the use envirnment. Tw types f life cycle tests were defined t be cnducted in sequence. Ambient Life Cycle Tests with a 50% depth f discharge were cnducted early t prvide data allwing a dwn-selectin f the best candidate cells fr use in the Integrated Envirnmental Cyclic Tests. Subcntractr defined Ambient Life Cycle Tests were cnducted early in the prgram by the manufacturing cmpanies n the biplar and prismatic cell design alternatives. The cmpanies tested their designs t different cnditins that were nt cmparable. One cmpany tested at 75% depth f discharge while the ther tested at 20% depth f discharge. In rder fr GRCI t cmpare perfrmance between the designs, a specific test plan was develped fr 50% depth f discharge. Specific design and perfrmance differences were recgnized t result in unique test cnditin requirements fr discharging and vercharging, fr example. Any cell design's specific test cnditins were described by the subcntractr and included in the Test Plans delivered with the test samples. T cmpare perfrmance data between the subcntractrs, the Ambient Cyclic Tests at 50% depth f discharge were specifically defined. Due t cell design and testing methds, the testing prcedures were nt identical. Hwever, each test cell attained ambient temperature between cycles t eliminate any thermal effects in subsequent cycles. T eliminate the thermal effects, a rest perid in the test sequence was required. In additin, active cling meth- 17

28 ds t attain ambient temperature in less time were acceptable and were specified by the subcntractr as part f the test methd. The test prcedure used by SAFT fr the Ambient Cyclic Tests at 50% depth f discharge was based n cells having an initial capacity f nminally 10 Ah. Each cell was fully charged using 2 hurs at C/2 + 3 hurs at C/20. The Ambient Cyclic Test prcedure was as fllws: Discharge fr 30 minutes at 1C Rest 30 minutes Charge fr 1 hur at C/2 + 1 hur at C/20 Rest 10 minutes Repeat Cycle The cells were fan-cled during the entire ambient cyclic test sequence. The rest perid allws the cell t attain ambient temperature prir t next test cycle. After every 50 cycles, a measurement f capacity was made using the fllwing methd: After the discharge at 30 minutes at 1C in the 50 th cycle, fully discharge the cell at C/2 t 0.9V/cell. Charge the cell 2 hurs at C/2 + 3 hurs at C/20 Rest 15 minutes Discharge at C/2 with cutff at 0.9V/cell The cells were fan-cled during the capacity check test sequence. Fllwing the capacity check, each cell was fully charged using 2 hurs at C/2 + 3 hurs at C/20. Then the cyclic tests were cntinued fr an additinal 50 cycles. The cell and battery perfrmance was cnsidered failed if the discharge capacity became less than 75% f the nminal r initial capacity. Likewise, failure was indicated if the vltage was less than 0.9V/cell r 75% f the battery nminal vltage. The cyclic perfrmance ver 200 cycles fr the cell designs is given in Figure 15 and Figure 16. N degradatin f perfrmance was apparent during this testing sequence. A full cyclic test scheme f a minimum f 600 cycles was planned but nt accmplished due t the time available within the prgram. With the perfrmance f the cells in ther tests at ambient temperatures shwing n detrimental respnse at +23 C, there was limited risk in the assumptin that further testing wuld result in a decrement f cell capacity perfrmance. Hwever, full cyclic testing shuld be accmplished n the final cell cnfiguratin r the cmplete battery design t establish a prjectin f cyclic lifetime.

29 Single Cell Test: grup 2 cells Cycling 50% DD: Capacity check j»- k p i ) O) ) r ; a = 15.0 ': ': -_ - ': Cycling cnditins : -Charge 2 C/2 + C/20 (Initial charge) -Discharge 30 1C -Rest 30 minutes -Charge 1 C/2 + 1 C/20 -Rest 10 minutes Even/ 50 cycles; caacitv check cvcle. -After 30 minutes 1C, residual dische -Charge C/2 + C/20 -Rest 15 minutes C/2 t 0,9 V/cell. rge@ C/2t0.9V/cel! End f life criteria -»-T3-Serial 1 T3-Serial 2 -*-T3-Serial 3 ) - -T3-Serial 3bis - -T3-Serial 4 j " 0.0,,,, i,,,, I,,,,! Cycle Number Figure 15 Capacity Check Every 50 Cycles Measured by Cell Capacity vs Cycle Number fr Each Cell Design Single Cell Test: grup 2 cells Cycling 50% DD: Vltage at 50% DD during Capacity Check Cycle I...I a O) =>- 3 a LI >. O O LI ^ 0) in m O) m f Cyciing cnditins: -Charge 2 C/2 + C/20 (Initial charge) -Discharge 30 1C -Rest 30 minutes -Charge 1 C/2 + 1 C/20 -Rest 10 minutes Every 50 cycles: capacity check cycle. -After 30 minutes 1C, residual C/2 t 0.9 V -Charge C/2 + C/20 -Rest 15 minutes C/2 t 0,9 V/cell. -T3-Serial3bis End fcf life criteria Cycle Number Figure 16 Cell Vltage at 50% Depth f Discharge During the Cell Capacity Check fr each Cell Design 19

30 5.4 INTEGRATED ENVIRONMENTAL CYCLIC TESTS The Integrated Envirnmental Cyclic Test is a set f 80 cycles defined by the Lckheed Martin Spec #16ZE374B, 18 June The 80 cycles simulate the battery cnditins experienced during flight checkut and engine start ver the thermal cnditins prjected in wrldwide peratins fr the F-16. Figure 17 is a graphical representatin f the 80-cycle test sequence, test cnditins, and the type f test t be cnducted. Table 5 is extracted frm the specificatin and explains the different types f tests. Fr this effrt, the test cnditins were adjusted frm thse defined in the battery specificatin t adapt t the size f the biplar and prismatic cells. Earlier, the capacity data shwed the cells had minimal if any discharge perfrmance at - 40 C. In additin, the cells wuld nt be used singly but nly in a battery cnfiguratin that wuld have a heating blanket. As a cnsequence, the test temperatures fr the lwer temperatures in the Integrated Envirnmental Cyclic Test were changed as fllws: -29 C changed t - 18 C, and -40 C changed t -29 C. The defined test sequence was nt changed. The defined rest perid between cycles was recmmended in the specificatin t be between 4-24 hurs. The thermal respnse f the equipment and the test samples was evaluated. Fr the single cell tests, a tw-cell test +70 C and cled t -40 C in a climatic chamber. The cell was mnitred and allwed t reach equilibrium at each temperature then the chamber was set t +23 C. The test sample reached the test temperature in nminally 5 t 6 hurs with a thermal delay f the chamber being 25 minutes t reach +70 C and 45 minutes t reach - 40 C. When the chamber was set t +23 C, the test cell stabilized at +23 C in less than 4 hurs fr bth temperatures. Therefre, the rest perid fr the test prcedure was nt less than 4 hurs. As an example fr the Integrated Envirnmental Cyclic Test, assuming the cell is fully charged, the cyclic set f cnditins at -18 C fr a single cell wuld be Rest 4 hurs t stabilize the cell at - 18 C. Discharge at- 18 C at 20A fr 10 minutes r until cut-ff f 0.9V/cell. Charge at- 18 C accrding t the determined cnditins fr the cell. Repeat the cycle in accrdance with the test plan. The test prcedure fr the peridic capacity check at +23 C fllwing the last cycle f a set was Rest fr 4 hurs t stabilize the cell temperature at +23 C. Discharge at 20A until reaching the cut-ff f l.ov/cell. Charge at 20A accrding t the determined cnditins fr the cell. Begin the next set f cyclic testing cnditins. Figures 18 and 19 present the Integrated Envirnmental Cyclic Tests data in terms f cell vltage and cell capacity, respectively, fr the cmplete 80 cycle sequence. N irregular data were generated. The cells perfrmed well and satisfactry under the entire cyclic test sequence. 20

31 Integrated Envirnmental Cyclic Tests Aircraft Battery System, Spec #16ZE374B, 18 June 1993 Nte: After each discharge, immediately recharge fr 80 minutes, and then rest fr 4-24 hurs Test Cycle Figure 17 Test Scheme fr Flight System Prfile (fr Vented Ni-Cd Battery Charger Perfrmance) Table 5 Descriptins f Test Cnditins fr Flight System Prfile with Reference t Figure 17 (Aircraft Battery System, Spec M6ZE3743B, 18 June 1993) #1 Nrmal Discharge a. Discharge battery at 20 Amps fr 10 minutes. (3.3 Ah) b. Immediately recharge fr 80 minutes. c. Rest fr 4-24 hurs. #2 Capacity Check a. Discharge battery at 20 Amps t 20 vlts. The discharge time must be greater than 27 minutes, b Immediately recharge fr 80 minutes, c. Rest fr 4-24 hurs. #3 Cld Temperature Discharge a. Discharge battery at 20 Amps fr 10 minutes. (3.3 Ah) b Immediately recharge fr 80 minutes, c. Rest fr 4-24 hurs. #5 Extreme Cld Temperature Discharge a. Discharge battery at 20 Amps fr 10 minutes. (3.3 Ah) b Immediately recharge fr 80 minutes, c. Rest fr 4-24 hurs. 21

32 ', l Single Cell Test Integrated Envirnmental Cyclic Tests: Flight System Prfile r > yßm f ~~»HMW*^ Specified Minimum Ceil Vitage (V) i- 60 f a> D I i i 11 i i i i i 11 i i i i i 11 i i 11 i i i i 11 i i 11 i i i i I ~ Cycle Number Figure 18 Bttm Curve: Cell Vltage after Discharge Cycle at Crrespnding Temperature. Tp Curve: End f Charge Cell Vltage Prir t Next Cycle at Crrespnding Temperature <, >> 35 '5 a 3 O Ml*, «M! I I I I Single Cell Test Integrated Envirnmental Cyclic Tests: Flight System Prfile IIS ; a I i L _ \ i Mi nimum Cell Capacity specified during capacity check cyple (Ap) illlhimi Cycle Number Figure 19 Cell Capacity Check at +23"C after Designated Cycle Number O 20 g

33 6.0 TEST SET Independent evaluatin and cnfirmatin f cell perfrmance was required by the Air Frce. The battery test labratry f the AFRL Prpulsin Directrate has the capability fr evaluatin f test cells. Fur prismatic cells were assembled tgether as a test set, Figure 20. Stiffened end plates and cmpressin straps held the fur cells tgether and sandwiched a thermistr between each cell fr temperature mnitring during testing. Three sets f fur cells were delivered fr test and evaluatin. Special handling and safety requirements were used during all characterizatin. Figure 20 Test Set f Fur Ni-MH Prismatic Cells Frm SAFT 23

34 7.0 PRE-PROTOTYPE BATTERY ASSEMBLY The Ni-MH batteries included 20 individual cells assembled int a case with a cnnectr and heater blanket. The pre-prttype battery was delivered with a test plan definitin similar t that prvided with the test cells. Figure 21 is the assembled battery shwing the cells and the intercnnectins between the cells. Figure 22 is the fully assembled and sealed Ni-MH preprttype battery. Figure 21 Layut and Intercnnectins f the 20 Cells in the Pre-Prttype Battery Figure 22 Fully Assembled and Sealed Ni-MH Pre-Prttype Battery With Cnnectr 24