Solar Powered Battery Charger Kevin McDowall, Joshua Ivaldi, Muhammad Mustaqeem Khatri, and Alfredo Elias Department of Electrical and Computer Engineering University of Connecticut Advisor: Dr. Sung Yeul Park Date 19 April 2013

Outline Motivation Specifications Buck Converter Topology Sensors Microcontroller Algorithm Design Details Results Cost Conclusion Questions

Motivation Decided to leave IFEC work and start new work on Solar Battery Charger for better design experience Design topologies are similar so will help us in transition

Specifications The goal of the project is to harvest energy from a 220W solar panel and use it to charge a standard 12V, lead-acid battery. Lead-acid battery characteristics.

Buck Converter Topology 24V ≤ Vin ≤ 48V Vout < 13.8V Buck converter is a step-down DC to DC converter Therefore, buck converter topology was chosen Block Diagram

Sensors Need sensors for feedback purposes The input voltage and current are monitored, as is the output voltage and current. This is done with current sensors and operational amplifier comparators.

Microcontroller Board The microcontroller chip is TMS320F28335, coded in C++. The board monitors input current, input voltage, output current, output voltage and current battery charge.

Control Algorithms The control board is coded to operate three different algorithms; Constant Current, Constant Voltage and Maximum Power Point tracking. Constant Current – The first stage of the charging process. Will charge battery to about 95% completion

Constant Voltage The second stage of the charging process. The battery is supplied 13V across its terminals until the full charge is reached.

MPPT Maximum Power Point Tracking (MPPT) – Sunlight conditions change, so there is need to constantly calculate maximum power available from PV panel

Design details: Power Circuit Schematic Isolator for signal transfer

Design details: Voltage Supply Schematic 12 Volt Supply 5 Volt Supply

Design details: Sensor Schematic Comparator Comparator Current Sensor

PCB Layout Altium Designer 4 layers Top Layer 5V Layer 3.3V Layer GND Layer

Results Slight errors in sensor readings Modification required in the gate driver Able to run all algorithms successfully

Board Cost The total cost to produce the power board is: $162.06 Cost of control board: $102.80 The cost of a 220W solar panel is: ~$350

Conclusion and Learning Experience We have achieved all specification and design requirements Learned: PV Model Battery Charging algorithms Design of schematic and PCB board Able to combine knowledge from courses such as microcontrollers, power electronics, and digital control systems

Questions???