1. PROJECT PRESENTATION Battery Swapping Reliability Wesley Lavender EMIS 7305

2. Presentation Outline Overview Scope Problem Analysis Overview Industrial Robots Performing Swap Charging Stations Results Conclusions Questions

3. Overview Battery swapping stations have been proposed by Better Place as a solution to the problem of electric vehicle batteries’ limited range. The Better Place switch stations are currently in the demonstration phase and use a mix of mature and immature technology. Better Place Switch Station

4. Scope Original Scope: Reliability, Maintainability, Supportability Analyzing the battery identification process, battery swapping process, and the charging of depleted batteries Refined Scope: Reliability only Analyze battery swapping process (including the clamping mechanism, the retrieving mechanism, and the moving tray) and charging stations

5. Problem Battery swapping is new and immature Little testing completed on reliability of battery swapping systems Complex system with a lot of moving parts

6. ANALYSIS Overview, Industrial Robots Performing Swap, and Charging Stations

7. Overview Selected Model: Exponential commonly used for electronic equipment constant failure rate model used in analyzing the ‘useful life’ period of an item’s life Failure rates and MTBFs used were measured during testing

8. Industrial Robots Performing Swap 3 Primary Components: Clamping mechanism: holds vehicle in place while swapping battery Retrieval mechanism: retrieves/inserts batteries Moving tray: contains clamping and retrieval mechanisms and moves batteries to and from vehicle Failure Rate (λ)MTBF (in hours) Clamping mechanism0.0000520,000 Retrieving mechanism0.000110,000 Moving Tray0.000062516,000 FIGURE 1: Industrial Robots failure rates and MTBFs

9. Industrial Robots Performing Swap Reliability Function: R(t) Clamping mechanism0.966 Retrieving mechanism0.905 Moving Tray0.911

10. Industrial Robots Performing Swap Components in a series configuration: Product Rule of System Reliability: R S (t) = (0.966)*(0.905)*(0.911) = 0.796 Failure rate: = 0.000213 MTBF S = 4,706 Clamping Mechanism Retrieval Mechanism Moving Tray

11. Charging Stations 5 identical, independent charging stations Need at least 3 in operation at all times R-out-of-N configuration (n=5, r=3) S1 3 out of 5

12. Charging Stations

13. Results R(t)Failure Rate (λ)MTBF (in hours) Industrial Robots 0.7960.0002134,706 Clamping mechanism0.9660.0000520,000 Retrieving mechanism0.9050.000110,000 Moving tray0.9110.000062516,000 Charging Stations 0.7960.000491,958 FIGURE 4: Summary of reliabilities, failure rates, and MTBFs

14. Conclusions Technology too immature for widespread commercial implementation Industrial robot system should use redundancy to improve reliability Charging stations should improve reliability of individual stations to improve overall reliability

15. Questions? References: "Better Place." Wikipedia. Wikipedia Foundation, Inc., 07APR2012. Better Place official website. www.betterplace.com. EMIS 7305 class notes.