• Team:– Brad Jensen– Will Klema– Nate Schares

• Client:– PowerFilm, Inc.

• Advisor:– Dr. Ayman Fayed

Solar-PoweredMobile Power Station

(MPS)

• Create a portable device that allows users to store solar energy to operate and charge their devices in remote locations. The device must also be capable of charging from an external source (AC).

Problem Statement

Conceptual Sketch

Use-Case Scenario• Military:– Individual Soldier Power Source– Charge Laptop, GPS, etc.

• Commercial:– Camping/Remote Destination– Personal electronics charging

Functional Requirements• Optimized for standard Solar Panel input – 4A @ 15V (60W) Amorphous Silicon

Panel• 100W minimum Lithium-Ion battery capacity• 12V DC input (with AC-DC Adapter)• Outputs:

• 5V USB output (USB 2.0 output)• 12V DC output• 120V AC output with switch

• Circuitry must be able to function in a temperature range of -25° C and 60°C• Charging LED Indicators/state of charge indicators• Charge Balancing Circuitry to keep Li-Ion Batteries balanced to prevent over or

under charging• Temperature sensor for batteries with alarm LED• Achieve 80% or greater efficiency on all outputs• MPPT Charge controller with rating of up to 200W (12A @ 15V – PowerFilm

Solar Quad) (optional)

Non-Functional Requirements

• The MPS shall be designed mainly for military soldier use

• The MPS should also be designed with options for commercial use

• The unit should have a weight of less than 5 pounds

• Unit should be manufactured for a cost of under $500 per unit

• The unit should easily fit inside a military backpack

Potential Risks and Mitigation• Overheating• AC Inverter• Climate Conditions• Battery Charging

• Electrical Shock• AC Voltage

• Overcharging Li-Ion Batteries• Hydrogen gas build up• Explosions• Li-ion very sensitive to overcharge

• Mitigation• AC Circuit Breaker• Monitor Battery Temp.• Charge Balancer

DeliverablesUpon completion of the project, the team will provide:

• Project Plan• Design Document• MPS prototype and PCB – Populated and tested for functional

requirements • Schematic diagram• Operational manual• Final report

Work breakdown

Team Leader: Nathan Schares• Organized meetings, Weekly Updates• Ordered Parts• Buck Converter Design• Research MPPT & Buck Converter

Communication Liason: Brad Jensen• Worked with PowerFilm Engineers• Buck Converter Design• Research MPPT & Buck Converter• Schematic Design

Webmaster: Will Klema• Designed & Updated Website• MSP430 setup • UART Communication• PWM• MPPT Algorithm

Cost Estimate

Costs to Date

Schedule

System Decomposition• Fart

Li-ion Batteries

Buck Converter

Microprocessor (MSP430)

Power Distribution

Circuitry

Solar Panel

Source

5VDC (USB)

12VDC

120VAC

External Power Sources (5VDC, and 12VDC)Voltage and

Current Sense

PWM Control Signal

Charge Control(BQ78PL114)

Feedback Voltage Sense

Maximum Power Point Tracking

• Optimized for standard Solar Panel input – 4A @ 15V (60W) Amorphous Silicon Panel

Buck Converter• Convert panel voltage (14-17) volts to approx. 12.5 volts for

charging 3 cell Li-Ion batteries• Impedance matching for maximum power• Capable of delivering up to 4 Amps from solar arrays (8A output)• 100 KHz switching frequency• Microprocessor controlled (MSP 430 , Texas Instruments)

Buck Converter Schematic

Buck Converter CalculationsVoltage and Current ripple calculations:

MSP 430• 16 bit ADC (3 channels)

• PWM generation with Timer A• UART communication• MPPT algorithm development

MSP 430

Voltage Sense:

Current Sense:

Charging Circuitry• BQ78PL114 Li-Ion charging chip , Texas Instruments

• Originally built for charging electric car batteries

• Capable of charging and delivering high currents

Schematic

Test Plan• An open circuit will be created on both the input and the output of the buck converter to enable measuring Input and Output current Power efficiency can be deduced Target is 90%• An oscilloscope and LabView software will be used to measure both the output current and voltage ripple to ensure operation is within the specified limits• Two full discharge/charge cycles will be run on the batteries to assure that the Li-Ion charging chip meets safety standards load is provided by Powerfilm as well as a purely resistive load.• Using the oscilloscope and LabView software we will measure the PWM output of the MSP430 to test the control loop stability and input/load regulation.

Project Milestones•May 7, 2010 – Test buck converter using microprocessor

and Li-Ion charging evaluation board (Testing functionality)

•Summer Break – Work on improving MPPT Algorithm, Finalize schematic layout and begin PCB layout

•September 10, 2010 – Test the design using phase one testing procedure

•October 29, 2010 – Finalize design, create deliverables

•November 19, 2010 – Submit Final Report

Current Status• Evaluation module phase

Built Buck Converter Tested Buck Converter with varying duty cycles

• Microprocessor Coding PWM generation with Timer A USART Setup Began MPPT Algorithm

• Li-Ion Charging Program and test Li-Ion charging chip during Finals week

Plan for next semester• Charging Chip

Program Battery Parameters Integrate into buck-converter

• MSP430 Implement MPPT algorithm Ensure buck-converter stability Determine MPPT sweep frequency

• MPS Inputs/Outputs Select DC/DC output converters Select 12V DC to 120V AC inverter Integrate input charging priority system