Project Description

Initially, I had this idea that I wanted to build a solar powered electric fence charger as a creative way to protect my chickens at home from the coyotes. I hypothesized that the circuit would be illustrated by the block diagram shown here.

I quickly discovered that this would be too large of a project for the amount of time I had available this quarter, so I decided to focus on the first 3 boxes which primarily revolved around designing a voltage regulator circuit that would enable me to use solar energy to maintain charge in a lipo battery. I decided that aiming to charge a 7.4V 2s Lipo battery with an 11V solar panel was my goal.

I chose the BQ24650 charging IC from Texas instruments because of its solar panel input voltage range from 5V to 32V, its specific application for charging Li-ion and Lipo batteries, and its built in MPPT function and integrated synchronous DC-DC buck converter.

Maximum power point tracking (MPPT) must be used in order to produce the most efficient charging results using the panel. While there are several different ways to implement MPPT, the IC that I decided to use already had MPPT built into it, therefore I did not have to worry about designing the hardware or coding the software, I just concerned myself with understanding it. The MPPT feature is described further on the Theory Page of this Wiki.

The aim of this class is to learn the basic methods of electric power analysis and design which includes learning the characteristics of various electronic power switches and learning about different switching topologies. To enforce these learning objectives, I have determined 3 objectives for this specific project:

1. apply the learned materials from class lectures and homework (primarily consisting of the mathematical reasoning behind MPPT and DC-DC buck converters)
2. design and build a solar charger circuit utilizing these concepts
3. have an operating solar charger for which I can test for switching efficiency and evaluate the effectiveness of the MPPT feature

Wiki Directory

• User Manual: Easy to follow instructions on using this project assuming each component is working properly.
• Theory: An overview of relevant theory to the project that was also discussed in class lectures.
• Schematic and PCB Design: A discussion of the motives behind each design concept.
• BOM : Useful information regarding the materials you need and corresponding prices and documentation.
• Build Plan: Detailed step by step build instructions
• Test Procedure: Updated test procedure I recommend following in order to mitigate errors.
• Results: Conclusions from the project thus far.

If you have any questions regarding the project, feel free to reach out to me. Cheers to a new project!