There are two main types of solar controllers (also known as solar charge controllers) : MPPT solar controllers and PWM solar controllers.

PWM- pulse width modulation solar controller: It is a type of current control, will switch the input current of the photovoltaic array in PWM pulse mode. As the battery tends to be full, the pulse width will shorten.

MPPT- Maximum power tracking solar controller. Multiply the voltage U and current I of the solar cell to get the power P, and then judge whether the output power of the solar cell reaches the maximum at this time. If the operation is not at the maximum power point, adjust the pulse width, modulate the output duty ratio D, change the charging current, and conduct real-time sampling again to determine whether to change the duty ratio. This optimization process ensures that the solar cells are always operating at their maximum power point to make full use of the energy output of the solar array.

Both solar controllers have their own advantages, as follows:

PWM

When the solar cell temperature is medium to high (between 45°C and 75°C), the PWM solar regulator is a good low-cost solution suitable only for small systems

MPPT

To realize the full potential of the MPPT solar controller, the array voltage should be much higher than the battery voltage. The MPPT solar regulator is the preferred solution for higher power systems (due to the smaller cable cross-sectional area and therefore the lowest overall system cost). The MPPT solar regulator will also gain more power when the solar cell temperature is low (below 45°C) or very high (above 75°C) or when irradiance is very low.