Here is a simple circuit that I made to charge my 14.4V 4s LifePo4 battery with solar power. MPPT stands for Maximum Power Point Tracking. In a normal PWM solar charge controller, it is basically just a switch which turns on and off when the battery is full, the problem with this is the solar panel voltage drops near the battery voltage hence dropping the output power. With MPPT, it will allow the solar panel at maximum power with the maximum voltage.
About the Circuit
The circuit uses CN3722 chip which make it simple and easy to build. Most MPPT are using a microcontroller which needed to be programmed which makes it hard to build for beginners.
Instead of using a potentiometer for adjusting the MPPT voltage, I just used a bunch of resistors in series with a jumper pads in parallel with its resistor. this will allow you to adjust the MPPT from 16.5V to 18.5V in 0.5V steps.
Here’s the layout that I designed using kicad.