MPPT solar charge controller 24 A

Greetings to all, my name is Valentina Ramirez, I am currently a student of electronic engineering at the University of Buenos Aires, today I want to show you my degree project, which is a solar charge controller based on Maximum Power Point Tracker.

I decided to develop this project due to the inefficiency presented by the use of chargers called PWM which, due to poor energy management, end up wasting around 25% to 35% of energy produced by solar panels, this is largely produced by the behavior that solar panels have to give their maximum power, which must have a specific voltage and currents in order not to saturate the cells of the panels.

but what differentiates a normal solar charger from an MPPT solar charge controller?

The answer is found in the objectives of the different solar chargers and how they are executed, as I had already explained, due to the behavior of the solar panels they are not a normal current source, but instead need a voltage and a specific current so that they can work at their maximum power, therefore if we connect a normal DC-DC source, which is also called a PWM charger, it will take out in a very abrupt way and without any control, all the energy it has, producing an abrupt drop in voltage in the solar panel that will ultimately be reflected in solar production.

On the contrary, the MPPT charge controller will seek to charge the battery with all the energy that is being generated, but the key is that it does so in a manner controlled by a microcontroller, thus finding the point where the panel voltage drops. abruptly and avoiding it, in order to find the exact point where the voltage and current are maximum to achieve the maximum power.

I said a moment ago that MPPT chargers need a microprocessor to control it, so which one will we use? For this design we will use an Atmega328 that will monitor, at high speed, the solar panel voltage, battery voltage, solar panel current and battery current, this microprocessor will be powered from the battery with a DC-DC source 5V based on LM2596

Moving on to more technical words, all this will be possible thanks to two resistive dividers that will be sensing the voltage of the batteries and that of the solar panels, additionally we will have two current sensors type ACS712-30A which will be capable of measuring currents of up to 30 amps. and transients of up to 100 amps, the reason for having both the voltage and the current of the solar panel monitored is because the system needs to calculate the current power by varying the cycle of the source PWM to modify the load and find the point full power.

The reason for measuring the battery voltage and current is simply to control the maximum values ​​set in the program, which would be the maximum battery voltage and the maximum charging current, highlighting that this system can work to charge any type of battery. battery, already Li-ion, LiFePO4, lead acid, gel, open batteries, among others, of course modifying the desired charging algorithm for charging the different types of batteries, in addition to that the system is open to BMS implementations for example To control the cell-by-cell charge in lithium batteries, thank you for your attention, if you have questions about the design or anything else, write in the comments, I will be happy to answer you.