The solar charge controller adjusts the charging process of the battery to ensure that the battery is charged correctly and not overcharged. The rating of the solar charge controller depends on the maximum input voltage and maximum charging current. These two levels determine how many solar panels can be installed.
The PWM or pulse width modulation solar charge controller has a direct connection from the solar cell array to the battery and uses basic fast switches to modulate or control battery charging. The switch (transistor) is turned off until the battery reaches the absorption charging voltage. Then, the switch begins to open and close quickly (hundreds of times per second) to reduce the current and maintain a constant battery voltage. Yes, but the problem is that the voltage of the solar panel is pulled down to match the battery voltage. This in turn pulls the panel voltage away from its optimal working voltage (Vmp) and reduces efficiency.
The PWM solar controller is a good low-cost option for small systems where a single solar panel is used for simple applications(Waterproof and Intelligent MPPT Solar Charge Controller).
Another type of solar controller can make the solar panel run at the optimal voltage to achieve the maximum power output, this is the MPPT maximum power point, tracking controller. The efficiency of the MPPT solar charge controller can be increased by up to 30%, depending on the battery voltage and the type of solar panel connected.
The functional principle of the MPPT solar controller is very simple-due to the varying degrees of sunlight (irradiance) falling on the solar panel during the day, the panel voltage and current will continue to change.
The maximum power point tracking controller is an efficient DC-to-DC converter used to maximize the power output of solar panels(high voltage dc converter). In order to generate maximum power, the maximum power point tracker scans the panel voltage to find the "best position" or the best combination of voltage and current to generate maximum power.