HIGH-RELIABILITY POUCH CELL CONNECTION AND COST ASPECTS OF A ROBUST BMS SOLUTION

Transcription

1 HIGH-RELIABILITY POUCH CELL CONNECTION AND COST ASPECTS OF A ROBUST BMS SOLUTION 3rd Israeli Power Sources, Batteries, Fuel-Cells, Smart-Grid & EV Conference May 29 th / 30 th 2013, Herzelia Dr. Uwe Wiedemann Alwin Lutz Can Kurtulus Dr. Volker Hennige Dietmar Niederl Martin Langmann AVL List GmbH Hans-List Platz Graz, Austria

2 FIVE ELEMENTS OF THE POWERTRAIN IC Engine Battery Transmission Electric Motor Controls / Electronics

3 OVERVIEW OF AVL s BATTERY ACTIVITIES Test equipment for pack testing turnkey solutions for battery labs + Testing & Benchmarking System validation Validation target: km cycle life 12 years calendar life EMC targets fulfilled System interaction ok Thermal & Mechanical Simulation; Cell Modeling Electrical & Mechanical Design Engineering Prototype, Generation 1&2 build-up BMS & MCU development (SW & HW)

4 CONTENT BMS requirements being a cost driver? BMS algorithms beyond SOC calculation Requirements for innovative connection method for pouch cells Results of connection solution Summary 4

5 BMS COST DRIVER - REQUIREMENTS Option A Option B Option C ASIL B BCM-MCU communication = CAN isolated HV & current measurement on board active/passive balancing ASIL B BCM-MCU communication CAN isolated HV & current measurement off board active/passive balancing ASIL B single PCB non-isolated low voltage standard I/O low cost cell interface 5

6 COST DRIVERS AND ALTERNATIVES OPTION A REQ: CAN bus between MCU and BCM for reliability COST: isolated CAN chips & local µc required BENEFIT: use distributed computing for system safety HV - HV + Ign, Batt,GND,HVIL and Vehicle CAN Bus Contactors & Pre-Charge Contactor Ctrl BCM BCM Communication and Control Thermal Control L P T Electronic System Cost 8% Communication (Isolated) 8% Connectors & Misc 12% Micro Controller 10% Sensor & Actuator I/O 12% Power Supply 50% HV & Cell Measurement + Balance Current Measurement (Safety) Current Measurement BCM 6% Communication (Isolated) 9% Connectors & Misc 13% Power Supply 15% MicroController 21% Sensor & Actuator I/O 36% High Voltage Measurement Fuse & Disconnect MCU MCU... MCU MCU Communication and Control MCUs 8% Sensor & Actuator I/O 10% Connectors & Misc 11% MicroController 14% Communication (Isolated) 17% Power Supply 40% Cell Measurement & Balance 6

7 COST DRIVERS AND ALTERNATIVES - OPTION B REQ: reliable communication, standard ECU, concentrated HV design COST: reduced µc count, low cost standard ECU, generic HV design BENEFIT: generic usage across multiple platforms HV - HV + Ign, Batt,GND,HVIL and Vehicle CAN Bus Contactors & Pre-Charge Contactor Ctrl BCM BCM Communication and Control Thermal Control L P T Electronic System Cost (33% reduction) 3% Communication (Isolated) 8% Micro Controller 9% Connectors & Misc 10% Power Supply 15% Sensor & Actuator I/O 55% HV & Cell Measurement + Balance Current Measurement (Safety) Fuse & Disconnect MCU MCU... MCU MCU Communication and Control Voltage & Current & Isolation Measurement BCM (40% reduction) 4% Communication (Isolated) 15% Connectors & Misc 22% Power Supply 24% MicroController 35% Sensor & Actuator I/O 0% High Voltage Measurement MCU (40% reduction) 7% Sensor & Actuator I/O 9% Connectors & Misc 0% MicroController 2% Communication (Isolated) 6% Power Supply 76% Cell Measurement & Balance 7

8 COST DRIVERS AND ALTERNATIVES OPTION C REQ: 60V max; compact packaging; no isolation required COST: distribute actuators and sensor to optimize system cost BENEFIT: easy integration into existing 12V systems Communication and Control Thermal Control L Contactor Ctrl P Contactors & Pre-Charge T Pos Current Measurement SMART MCU 12% Sensor & Actuator I/O 5% Connectors & Misc 16% MicroController 5% Communication 12% Power Supply 50% Cell Measurement & Balance SMART MCU On/Off CAN Communication and Control 8

9 OUTLOOK: FUTURE BMS ARCHITECTURE low cost communication for HV to LV system communication highly integrated system ICs for cell voltage measurement and balancing function including ISO safety support simplified contacting system for cell to electronic interface multipurpose smart module controller for < 60 V systems mechanical contactors replaced by smart electronic switches low cost current measurement system 9

10 CONTENT BMS requirements being a cost driver? BMS algorithms beyond SOC calculation Requirements for innovative connection method for pouch cells Results of connection solution Summary 10

11 BMS APPLICATION SOFTWARE NEW CHALLENGES State of the art BMS ASW usually calculates: state of charge state of health (basic version) state of function (i.e. power limitations) thermal behavior These are essential functions for vehicle operation of a production level BMS, but How do we determine when a pack seems to be in relatively good condition, whereas in reality it is about to fail? How do we know how long our pack will last? 11

12 BMS APPLICATION SOFTWARE HOW TO DETECT EARLY CELL FAILURES AVL s cell wear detection function monitors cell SOC deviations compared to the average monitors cell resistance deviations compared to the average. early detection of impending cell faults (unexpected SOC or resistance deviation warning before pack failure to avoid vehicle breakdown cell voltage cell voltage - average cell voltage negative slope indicating a lower cell resistance average cell voltage open-circuit voltage time offset related to higher SOC level average cell over-voltage cell voltage red: higher SOC, lower resistance cell voltage blue: higher SOC level, higher resistance over-voltage Fig. a) cell voltage charging. cell voltage red: higher SOC, lower resistance cell voltage blue: higher SOC level, higher resistance Fig. b) linear model for cell voltage deviations. 12

13 BMS APPLICATION SOFTWARE MID-TERM LIFE PREDICTION tracking of capacity and resistance changes in modules tracked over time tracking function compensates influencing factors like temperature mid-term life prediction based current resistance and capacity evolution. pack degradation and performance input for warranty life time assessment validations pack life time cost model validations geographical and usage effects on pack life 13

14 BMS APPLICATION SW CELL WEAR WARNING Measurement data showing response to failing cells in a pack. Error manager: warning flag due to 30% higher cell resistance (detected after 100s) After two weeks of battery operation, the detected cell failed completely: +100% increase in resistance... 14

15 CONTENT BMS requirements being a cost driver? BMS algorithms beyond SOC calculation Requirements for innovative connection method for pouch cells Results of connection solution Summary 15

16 CLINCHING AS CELL CONNECTION TECHNOLOGY Clinching 16

17 CELL TAB CLINCHING State of the art: Ultrasonic / Laser Welding AVL innovation: Cell Tab Clinching Testmodule (2P config.) complex busbars are necessary busbar made out of Al and Cu interconnection of AL and CU required very accurate positioning of busbar and cell terminal necessary parameters difficult to obtain no busbars required between cells, direct connection possible (1P configuration.) insensitive to positioning tolerances of the cell tabs during joining process 17

18 CLINCHING AS CELL TERMINAL JOINING PROCESS easy and fast operation stemp binder parts anvil Detailed mesh for considering contact zones due to clinching result connection accessibility part thin walled detachable undetacheble one sided double sided with prepunch without prepunch 18

19 TESTS ON CLINCHING CONNECTION METHOD electrical inspection vibration electric resistance thermal behavior resistance over temperature salt water spray test mixed gas test electrical assessment section cuts pull test peeling test

20 CONTENT BMS requirements being a cost driver? BMS algorithms beyond SOC calculation Requirements for innovative connection method for pouch cells Results of connection solution Summary 20

21 TESTS ON CLINCHING CONNECTION METHOD vibration test ok electrical resistance tests R Clinching ~ 200 A for one tab to tab connection R of tab material (20mm) ~ 60µΩ (measured with Micro Centurion II Raytech) ok thermal behavior tests Aluminum tab heats up more than the clinching points ok 21

22 RESISTANCE TEST OVER TEMPERATURE CYCLE WITH DIFFERENT MATERIAL COMBINATIONS material combinations Al-Al-Cu Cu-Al-Al Al-Cu-Cu Al-Cu-Al Cu-Cu-Al Cu-Al-Cu time [min] 22

23 RESISTANCE TEST OVER TEMPERATURE CYCLE WITH DIFFERENT MATERIAL COMBINATIONS Climatic cycle test with controlled profile. ok Resistance continuously measured. ok 23

24 SALT WATER SPRAY AND MIXED GAS TEST Mixed gas test: NO2: SO2: CI2: H2S: nitrogen dioxide sulfur dioxide chlor hydrogen sulfide Temperature: 25 ± 1 C Relative humidity: 75 ± 3 Time: 21 days Salt water spray test: Temperature: 35 C ± 2 C Amount: 1.5 ± 0.5 ml/h Sodium chloride: 50 5 g/l ph-value: 6,5-7,2 Time: 7 days

25 SALT WATER SPRAY AND MIXED GAS PULL AND PEELING TEST results shown in force-time graph measured: peak-force 25

26 SALT WATER SPRAY AND MIXED GAS MICROSECTION Measured the rest ground height ok Measured the undercut ok Interference after salt spray test and mixed gas test ok 26

27 CLINCH TOOL for each clinch 4 clinch points made parallel clinching is possible Process monitoring by force-displacement characteristics cycle time for 10 clinches: ~10sec manipulation time: ~5sec current prototype tool dimensions 27

28 CLINCHING AS CELL CONNECTION TECHNOLOGY SUMMARY cost-effective tool (<< 1/5 of laser welding) no heat input insensitive to positioning tolerances short cycle time (parallel execution + multiple points) different material combinations and multiple layers can be connected with the same tool (e.g. 1p and 2p connections) cost reduction by eliminating parts of the cell connector process monitoring by force-displacement characteristics possible direct combination of different materials (e.g. Al / Cu) no pre-treatment of the tabs required vibration module 28

29 CONTENT BMS requirements being a cost driver? BMS algorithms beyond SOC calculation Requirements for innovative connection method for pouch cells Results of connection solution Summary 29

30 SUMMARY & CONCLUSION Lower cell price increases pressure to reduce system cost High cost saving potential in BMS by choosing appropriate requirements New BMS algorithms maximize usage of battery system Innovations in pack engineering and thermal integration show good potential for further cost reduction. 30

31 AVL BATTERY SOLUTIONS THANK YOU FOR YOUR ATTENTION! For more information 31