Solar System Controller: PWM V.S. MPPT

I. PWM solar system controller (pulse width debugging method)

pwm controller pulse width modulation (PWM) refers to the use of the digital output of the microprocessor to control the analog circuit, is a method of digital encoding of analog signal levels. Controlling analog circuits digitally can significantly reduce the cost and power consumption of the system. This comes into play when the battery pack is already full. During charging, the solar charge controller allows the current generated by the PV panel to reach the target voltage for the charging phase of the controller. When the battery reaches its target voltage, the controller will switch between the battery bank and the panel array. The battery array will then be disconnected, thus regulating the battery voltage and making it constant. This fast switching method is called PWM, and it works to ensure that your battery pack is charged while preventing overcharging.

The charging efficiency of the PWM controller is affected by the temperature, and the charging efficiency is best when the solar cell temperature is around 45~75℃.

II. MPPT solar system controller (maximum power point tracking)

MPPT or Maximum Power Point Tracking provides an indirect connection between the battery pack and the PV array. This indirect connection consists of a DC/DC voltage converter that receives the additional PV voltage and converts it to additional current at a lower voltage without losing power.

The MPPT controller detects the solar panel’s generation voltage in real-time and tracks the highest voltage-current value (VI), allowing the system to charge the battery at maximum power output. It is applied in solar PV system to coordinate the work of solar panel, battery and load, and is the brain of PV system.

PWM V.S MPPT Solar System Controller

Cost

MPPT solar controllers are a bit more complex and costly, usually several or even tens of times more expensive than PWM solar controllers, and are capable of adjusting the input voltage to obtain the maximum energy from the solar panels. charge the battery at maximum power output.

System

Compared to PWM solar controllers, MPPT solar controllers have a maximum power tracking function, which ensures that the solar panel is always at maximum power output during charging without being affected by temperature, and is naturally more efficient than PWM in terms of charging efficiency. In addition, PWM solar controller can only be used with the relevant voltage, such as 12V system panels can only be used with 12V controller and battery, suitable for some small off-grid systems below 2kw, simple structure, user-friendly wiring, the price is also relatively cheap.
In general, solar panel voltage between 12V-170V can be used, and battery voltage 12-96V is adjustable, which is more applicable and suitable for large off-grid power generation systems above 2kw, with high efficiency and flexible component configuration.

Temperature

If under cold temperature conditions, the MPPT controller will have more advantages than PWM. This is because as the operating temperature of the solar module decreases, the Vmp (maximum power voltage) will be lower than when the temperature is higher. With the MPPT controller, the power generation voltage of the solar panel can be monitored and the maximum voltage and current values can be tracked, allowing the system to charge the battery at the highest efficiency by outputting the power at the highest point. This makes MPPT controllers more effective than PWM controllers at low temperatures. However, when these when solar panels are used in higher ambient temperatures (40 degrees Celsius – 70 degrees Celsius), their Vmp will drop and the peak power point will operate at a voltage close to that of a 12V battery. Since there is no excess voltage to transfer in this case, the utility of MPPT will become unnecessary. This nullifies the advantage of MPPT over PWM.

In summary, to make it easier for you to choose the controller you need, here is a summary of how PWM charge controllers compare to MPPT charge controllers. In general, no one technology is the best and it is best to check the application, the conditions, the features you need, and your budget before choosing a controller for you.