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How does a PWM solar charge controller work ?

A PWM solar charge controller regulates the voltage and current supplied to photovoltaic array to maintain optimal operations during different lighting conditions. They are widely used in automotive applications such as ignition control and transmission operations.

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In this post, I will explain the functions of a PWM solar charge controller, its working principles as well as its advantages.

What is a PWM Solar Charge Controller?

Normally, solar panels are designed to operate at a specific voltage. However, batteries operate best at a specific voltage. Therefore, a PWM solar charge controller is that which regulates the voltage for charging the batteries.

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A PWM solar charge controller regulates the current and voltage by using pulse width modulated techniques. The controller has a power semiconductor device, which is usually a voltage source inverter. It switches a power transistor on and off with a high frequency pulse-width modulated signal. The frequency can range from 100 to 1000 hertz. The longer the transistor is on, the more current it allows to flow. The shorter the transistor is on, the less current it allows to flow. The controller analyzes the voltage and current on the panels and sends a pulse width modulated signal to the transistor that controls the current to the panels. As a result, the voltage and current supplied to the PV array are kept at the optimal levels. A PWM solar charge controller can be analog or digital.

Functions of PWM Solar Charge Controller

The main function of a PWM solar charge controller is to protect the system from over-voltage and over-current. Another function of a PWM solar charge controller is to maintain a constant voltage and current to the photovoltaic array at all times. The solar charge controller regulates the voltage and current supplied to the photovoltaic array to ensure that the voltage does not rise above the safe level and current does not drop below the safe level.

Working Principles of PWM Solar Charge Controller

When the voltage at the terminals of the solar panel drops and current starts increasing, the PWM solar charge controller immediately responds. The controller starts decreasing the current flowing into the solar panel and keeps the voltage at the terminals of the solar panel at the optimal level.

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When the voltage at the terminals of the solar panel rises, the controller immediately responds. The controller starts increasing the current flowing into the solar panel and keeps the voltage at the terminals of the solar panel at the optimal level. As a result, the voltage and current supplied to the photovoltaic array are kept at the optimal levels at all times.

PWM solar charge controller

Advantages Of Using PWM Solar Charge Controllers

  • The efficiency of the PWM solar charge controller is higher than that of  MPPT solar charge controller.

 

  • PWM solar charge controllers are easy to install and require minimal maintenance and monitoring.

 

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  • They are relatively less expensive than MPPT solar charge controllers.

 

  •   They provide better performance than MPPT solar charge controllers.

 

  •   They are safe to use, unlike MPPT solar charge controllers that may lead to the risk of voltage or current excursion.

 

  • They are widely used in residential and commercial photovoltaic systems.

 

  • They can operate over a wide voltage range, from 12 V to 1000 V.

 

  • They can operate over a wide current range, from 0.1 A to 50 A.

 

  •  They require minimal wiring and can be easily integrated with batteries.

 

  • They can be connected to non-series strings.

 

  • PWM solar charge controllers can be used in both off-grid and grid-tied systems.

 

  • They can be used in high temperature environments.

 

  • They can be used with lead-acid , and lithium-ion and gel-cell batteries.

 

  • PWM solar charge controllers can be used with AGM, deep-cycle ,  nickel-cadmium and silver-zinc batteries.

Conclusion

PWM stands for Pulse-Width Modulation.The main function of a PWM solar charge controller is to protect the system from over-voltage and over-current

When the voltage at the terminals of the solar panel drops and current starts increasing, the PWM solar charge controller immediately responds. The controller starts decreasing the current flowing into the solar panel and keeps the voltage at the terminals of the solar panel at the optimal level.
The efficiency of the PWM solar charge controller is higher than that of  MPPT solar charge controller and they are easy to install.

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