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Preliminary Design Review 1 Team Members: Chris Douglas Project Manager David Hooker Lead Research, Webmaster James Randall Liaison, Budget Manager Sponsors: Naval Surface Warfare Center: Acoustic Research Detachment, Bayview ID Advisor: Dr. Gregory Donohoe, University of Idaho Mentor: Dr. Herbert Hess, University of Idaho

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Problem Statement, Specifications, Deliverables Current System, Situation Design Concepts Trade Study Equipment Return on Investment Timeline/Future Work Challenges 2

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The Large Scale Vehicle 2 (LSV2) is an autonomous electric submarine used to study acoustic properties of propulsion systems. The Acoustic Research Detachment 3 (ARD) has requested improvement of capacity retention over the course of the propulsion batteries life cycle.

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Document current charging configuration with scheme advantages and disadvantages Research of potential changes to system to extend capacity retention Develop a cost-benefit analysis of implementing a new charging scheme Produce computer simulations of current and alternate configurations Construct lab scaled model of current and alternate schemes 4

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Current System Report Trade Study Selected Choices Summary Overview of Rejected Proposals Cost-Benefit Report Lab Test Report Proof of Safety Report Computer Simulation 5

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6 1. CC(45A/string) until 2.35V/cell 2. CV until 6.25A/string 3. CC for 3 hours with 2.50V/cell voltage limit2.50V/cell voltage limit Main Charge Overcharge 1680 2V batteries divided into 4 parallel strings Approximately 15min checks Batteries decommissioned @ 4 years(approx. 80% capacity)

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Human charge control can lead to undercharge or overcharge Both OC and UC can lead to battery life degradation Charging infrastructure maxed Chargers working at max current wiring from chargers to sub at max current Power grid already overloaded Aux. battery charge ~ 12 hours Two types of chargers readily available 7

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Extend useful life of batteries Reduce expenses over long term Reduce submarine downtime over long term resulting in higher return for taxpayer dollars Reduce the capacity loss of batteries over current service life Maintain underway duration over service life 8

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Automate System Free up technicians for other purposes Reduce risk of error of human control Improve Oxygen recombination efficiency(ORE) Reduce outgassing Decrease energy waste 9

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Zero Delta Voltage (ZDV) Concept Max current charges until 70% return of charge Constant Current (C/5) until ZDV is reached ZDV is defined as a limit in change in voltage between two readings A reading is defined as 30 second averages of voltage readings 10 Voltage

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Pros Accurately detects end of charge cycle Reduces human error during charge cycle Reduces possibility of detrimental undercharge/overcharge Possible 100% increase of battery life Cons Will need to be tested on multiple battery system Variable voltage termination limit over life of batteries 11

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Current Interrupt (CI) Concept Used after primary charge has completed (overcharge) Charge algorithm consists of a pulsed current CI is employed until 10% overcharge has been achieved 12...

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Pros Allows cooling period for batteries preventing excessive thermal degradation Allows for chemical reactions to stabilize during the off period leading to higher ORE Can be used independently of main charge method Cons Unknown change in charge time Setup of system may be complex Normally employed after a fast charge algorithm has delivered 100% of depleted charge 13

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Fast Charging Start with large current pulses (up to 4C) Monitor voltage and step down current each time voltage limit is reached 14

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15 Pros Is an extremely fast charge method Increases capacity retention throughout life Cons Requires enormous amounts of current (up to 600A) Generates large amounts of heat

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16 ItemMethodWeight CI/CVZDVCIFC Cat Caps Software Complexity0.270.240.2 0.33% Power Requirements0.450.540.30.10.66% Shore Power Considerations1.5 0 15% Rewiring of both Barge and Vessel0.20.180.20 2% Difficulty of Implementation0.450.350.40.20.45% Charge available for Underway1.21.61.821.620% Expected EOL Capacity0.30.60.910.810% External Interfacing of Controls?????8% Reduction in Charge time?????1% Cost of Implementation?????5% Long term Costs reduction?????25% Higher score is better4.375.015.23.45.4100% 39%

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CI and ZDV require testing Charge module capabilities unknown Testing is required to determine charge time Long term effects to be determined 17

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Software capable of accurately simulating cycle life has yet to be discovered State of health simulation is unfeasible at this time due to: Varying discharge rates during each test run Varying internal characteristics and chemical composition over battery life Varying and unknown cell temperatures for charge and discharge cycles Development contingent upon lab data 19

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20 ItemDescriptionQty Base Cost Total BatteriesNew LSV2 battery (2025 Lead) 6 $340.00 $2,040.00 Charge/Discharge System Arbin BT2000 / AeroVironment ABC- 150 or ABC-5 1 PENDING Catalyst CapsOxygen Recombination Catalyst 3 $35.00 $105.00 Total PENDING

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CONTINUED USE OF SYSTEM BENEFITS OF NEW SYSTEM $593,000/4 years for Main battery replacement Labor costs of replacement process Extending battery service life by at least 50% yields savings of $50,000/year (not including man hours) Length of underways can be maintained over longer period of time yielding more data collected per run 21

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State of health simulations non-existent Time constraints for cycle life testing Managing multiple test cases Access to charger control module Access to /Purchase of testing equipment 22

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Schedule with design of charge/discharge system Alternative budget to be determined 23

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