What is difference between PWM and MPPT charge controllers?

PWM Charge Controllers: A Legacy Technology

PWM charge controllers have been around for decades, and they’re still widely used in many off-grid applications. These controllers work by simply switching the solar panel array on and off at a high frequency (typically between 50-100 Hz) to control the flow of energy to the battery. This approach can lead to energy losses, especially when the solar panel array is partially shaded. For example, if a PWM controller is set to charge a 12V battery from a 12V solar panel array at 10% capacity, it might only be able to deliver 1.2 amps, resulting in a 10% efficiency loss. This is because the controller is not optimized to handle partial shading or variable input voltages.

MPPT Charge Controllers: The Future of Charge Control

MPPT charge controllers, on the other hand, use advanced algorithms to constantly monitor the solar panel array’s voltage and current output, and adjust the charging rate to maximize energy harvesting. This approach can lead to significant efficiency gains, especially in partial shading conditions. For example, an MPPT controller can take a 12V solar panel array with 10% capacity and deliver 12 amps to a 12V battery, resulting in a 20% efficiency gain over PWM. This is because the MPPT controller can adjust its charging rate to match the solar panel array’s maximum power point, even in the presence of partial shading. When choosing between PWM and MPPT charge controllers, consider the size and cost of your solar panel array, as well as the type of battery bank you’re using (e.g. flooded lead-acid, lithium-ion).