Mid Semester Presentation

Team Members Chapman, Jonathan Duties: Recharging Circuit Major: Electrical Engineering Dang, Quoc Duties: Power Circuit, Website Major: Computer Engineering Grice, Quintin Duties: Power Circuit Major: Electrical Engineering Teeple, Richard Duties: Communication Major: Computer Engineering Smith, David Duties: Fault Protection, Documentation Major: Computer Engineering

Project Origin This project stemmed from the curiosity of Dr. Marshall Molen and the EcoCar competition. 8 Lithium ion cells CAN-bus

Overview: Problem Solution Constraints Technical Practical Approach Progress References Questions

Problem When dealing with Lithium ion technology, the following aspects must be taken into consideration: Safety Communication System Life

Solution A cost efficient rechargeable battery system that offers the following: selective charging over-all current monitoring individual cell temperature and voltage monitoring CAN-bus communication

Technical Constraints: Name Description Battery Technology The technology used to output voltage from the REBATEM must be lithium ion cells. AccuracyVoltage must be measurable between 0 and 5 volts with a tolerance of ± 0.1 volts. Current must be measurable between 0 and 80 amperes with a tolerance of ± 10 milliamps. Temperature must be measurable between -30 and 200 degrees Fahrenheit with a tolerance of ± 2 degrees. Cycle Life / Capacity The REBATEM must maintain at least an 80% state of charge for the individual cells and a minimum of a 400-cycle life. Fault ProtectionThe control mechanism must disconnect the cells from the system when the temperature rises above 175 degrees Fahrenheit or when the current through the cells passes 80 amperes. It must also prevent overcharging a cell by slowing the charge rate when the cell’s state of charge reaches 80%. OutputThe REBATEM’s output voltage must be within the range of 14 to 16 volts. Its current hour rating must be between 3.4 and 3.8 amp hours. CommunicationThe battery management system must communicate cell voltages, temperatures and current to external devices.

Economic If mass produced on its current scale, the REBATEM must be affordable to the general public. A target cost of $250 provides a small profit of approximately $100. Parts alone must cost no more than $150.

Safety The device must meet the standards of UL 1642, which states that users must be protected from risk of explosion or fire due to any instability of the Li-ion cells [1]. Cell monitoring must ensure that the temperature remains within a safe operating range to uphold this UL specification.

Cell Geometry Prismatic Cylindrical VS [1][2]

Advantages Disadvantages Can be shaped to fit packaging restrictions Better dissipater heat lower energy densities Higher manufacturing costs No venting system to release internal pressure build-up Must use heavier metal to prevent bulging from pressure build-up Prismatic

Advantages Disadvantages High energy density Good mechanical stability Can withstand high internal pressure build-up Resealable venting system Poor dissipater of heat Packaging must be designed around available cell sizes Cylindrical

Types of Lithium ion Cells Cobalt ChemistryNominal Voltage Charge Voltage Limit Energy density Wh/kg Cobalt3.6V4.20V Manganese V4.20V Polymer3.7V4.20V Phosphate V3.6V Pros and Cons: [5] Manganese Polymer Phosphate

Cell Configuration Series of eight Eight in parallel Series of four in parallel Series of two in parallel

Evaluation: Output Voltage Continuous Current Peak Current Amp Hours Series of eight V A A Ah Eight in parallel V A A Ah Series of four in parallel V20 – 40 A76 – 80 A3.8 – 4.2 Ah Series of two in parallel V40 – 80 A152 – 160 A7.6 – 8.4 Ah

Temperature Sensing Resistance Temperature Detector (RTD) Integrated Circuit (IC) Pros and Cons: Supply Voltage Supply Current Temperature Range Cost (each) RTD< 10V< 1mA ˚F> $2 IC V A-50 – 300 ˚F<$2

Charging Integrated Circuit (IC) Independent Voltage and Current Loops Stand Alone or Uses Low-Cost μC Built-In Linear Regulator Power μC Charging-Current-Monitoring Output

Cell Geometry Prismatic Cylindrical [1] [2]

Type of Cell Hi-Polymer Li-ion cells [3] Specifications Capacity mAh Cycle life> 500 Charge rate1.9 A Max. Discharge Rate 38 A Max. Size6.0X35X96 mm Weight1.4 oz (40 g) [3]

Temperature Sensor RTD [7] Integrated Circuit [6]

Timeline JanuaryFebruaryMarchAprilMay Research Ordering Parts Hardware Design Constructing and test Prototype Working Prototype

References: [1] "Li - ion Battery." [Online] Available: network.com/b2b/88/89/445/page6/48031/li_ion_battery.html. [2] "INOVA T4 Tactical Flashlight." [Online] Available: [3] [Online] Available: [4] “Battery packaging - a look at old and new systems ”[Online] Available: [5] “The high-power lithium-ion” [Online] Available: [6] [Online] Available: [7] [Online] Available: nXLEDpLtU15A%3d

Any Questions?