1. 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

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

3. 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

4. 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.

5. 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

6. 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.

7. 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.

8. 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

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

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

11. Design details: Power Circuit Schematic
Isolator for signal transfer

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

13. Design details: Sensor Schematic
Comparator
Comparator
Current Sensor

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

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

16. 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

17. 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

18. Questions???