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

Motivation

Specifications

Buck Converter Topology

Sensors

Microcontroller

Algorithm

Design Details

Results

Cost

Conclusion

Questions

Outline

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

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

Current Sensor

Comparator

Comparator

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???