Advanced Terminal Design for Prismatic Li-Ion Cell

Advanced Terminal Design for Prismatic Li-Ion Cell

Eric Quee, EaglePicher Technologies

Mike Pollack and Rich DiDomizio, EnvirOptics, Inc.

2015 NASA Aerospace Battery Workshop November 17-19, 2015

Huntsville, Alabama

2 Copyright© 2015 EaglePicher Technologies, LLC

Outline

•  Existing Terminal Design Issues •  Advanced Terminal Design Objectives •  Qualification Test Plan and Initial Results •  Summary


Existing Terminal Design

•  Spade type terminal •  Positive Terminal 1100 Aluminum with Nickel plating •  Negative Terminal 101 Copper with Gold plating •  Terminal through hole bolt torqued to 20 in-lb •  Positive terminal known to relax under compression

–  Reduced terminal to lead contact force –  Increased resistance at the terminal interface

Terminal Tightened


Advanced Terminal Design •  Design Objectives

–  Provide robust electrical connection, not through threads –  Torque to 40 in-lb without backup nut –  Capable of resisting 60 in-lb of torque without movement

or loss of hermetic seal –  Mechanically stable over mission life, up to 15 years –  Fit in Gen 1.1 cell format –  Applicable for both positive and negative terminals

•  Design Features –  3/8-24 UNF 2A male thread 1.0” long –  0.600 diameter shoulder for direct electrical contact with

lugs –  Seal leak rate < 1.0 x 10-8 atm-cc/sec

–  Maintain hermetic seal at -40 to +75°C –  Terminal resistance less than 30 µΩ –  Nickel plating on both terminals


Qualification Test Plan •  Three separate tests

–  Initial baseline •  Insulation resistance •  Leak rate •  Resistance •  Torque resistance •  Tensile strength

–  Normal qualification •  -40 to +75°C, 6 hour dwells, leak test at temperature, two cycles •  CW torque after temperature exposure •  CW torque to failure

–  Accelerated life testing – 35 Amp current flow reversed daily •  0 to 75°C at > 80% RH, 11 hour dwells, 10 cycles

–  Accelerated ground storage •  5 to 75°C at > 80% RH, 15 minute dwells, 1020 cycles

–  Accelerated ground integration, testing •  -40 to 75°C no measurable humidity, 15 minute dwells, 756 cycles

–  Accelerated LEO mission


Test Flowchart Summary


Initial Testing and Normal Qualification Flowchart

Initial Testing for all Seals and Terminals

Destructive Lot Acceptance Testing Specified by EPT on each production order


Accelerated Life Test Summary


Accelerated Life Test Detail


Accelerated Life Test - Terminals


Accelerated Life Test - Controls


Test Results to Date

•  Tensile Test – Terminal only Sy = 25,300 psi

•  Torque Test – Terminal only No deformation at 65 in-lb torque

•  Bend Test – Terminal only Failure at 95 in-lb

•  Terminal Resistance –  13 samples tested –  Resistance measured between a

fixed length of 0.870 “ –  Resistance measured at 0° and 90°

rotated then averaged –  Resistance range 10.3 to 10.65 µΩ


Summary

•  New positive terminal has been designed to address material relaxation

•  Terminal assemblies are being tested including –  Initial characterization –  Normal qualification testing –  Accelerated life testing

•  Accelerated life testing to simulate on ground and LEO mission requirements

•  Initial results are positive


Thank You

Documents

Advanced Terminal Design for Prismatic Li-Ion Cell