Solar Charge Controller

What Is a Solar Charge Controller and How Does it Work?

Proper use and operation of a solar panel system requires a full understanding of its components. It's not only the panels, battery, and inverter that work together to generate electricity. More components contribute. One of the most essential yet overlooked components is the solar charge controller. 

If you’re unfamiliar with this, you’re in the right place. This article explains everything you need to know about solar charge controllers. This includes what they are, how they work, the types you can get, and why you might need one for your solar panels


What Is a Solar Charge Controller? 

A solar charge controller is a vital piece of equipment. It helps maximize the output of residential and commercial solar panel systems. It regulates the flow of energy from the panels into the battery. It’s responsible for three essential functions: 

  • Prevents the battery from overcharging
  • Regulates the charging current
  • Supplies appropriate amount of voltage for the battery

The solar panels sometimes collect more energy than their batteries can handle. This can lead to dangerous consequences. The controller manages that energy flow. This way, it ensures that the power the battery receives isn’t more than the load it can handle. 

Remember that solar panels can produce varying amounts of electricity. The amount depends on many factors, such as weather conditions. Without the charge controller, the whole system couldn’t operate at its full potential. Moreover, the battery would degrade. 


How Does It Work? 

The charge controller measures the voltage of the battery and the solar panels. It then adjusts the flow of electricity between the two accordingly. If the battery is 100% charged, the controller will reduce the amount of electricity flowing into the battery. But if the battery is low in charge, the controller will increase the flow instead.

Some charge controllers can track the weather and adjust the charging parameters of the battery. They track the amount of sunlight available. Based on that, they adjust the parameters to ensure the battery’s charging efficiency.  

Here’s how the controller regulates the charge and provides protection to the system: 

  • Prevents reversing of current from the battery to the solar panels when the system isn’t generating power
  • Switches off the battery once it reaches an excessively low voltage
  • Lowering the voltage when the temperature of the battery rises


3 Types of Solar Charge Controllers

Generally, there are two main types of solar charge controllers: Pulse Width Modulation (PWM) controllers and Maximum Power Point Tracking (MPPT) controllers. But, some also use another older type: the Simple 1- or 2-stage Controllers. 

Here’s how they’re different: 

1. Pulse-Width Modulation (PWM)

Pulse-Width Modulation (PWM)

PWM controllers are small and affordable charge controllers and often come as a standard with small solar systems, like RV ones. 

These controllers regulate voltage from the panels to the battery at a fixed rate. They gradually reduce the current output in the system as the battery charges. Once the battery is fully charged, the PWM controller will keep it full by providing small amounts of power without overcharging. 

Remember that PWM controllers are designed for solar panels that match the battery voltage. This means that if you want to charge a 12V battery, you need solar panels with a rated output of 12 volts. 

Compared to the other types, this type of controller is simpler, more affordable, and low maintenance. However, since it’s designed for smaller, simpler systems, you can expect it to be less efficient than the other main type – MPPT controller. 

2. Maximum Power Point Tracking (MPPT)

Maximum Power Point Tracking (MPPT)

MPPT charge controllers are also known as smart DC-to-DC converters. They’re more advanced than the PWM controllers since they can match a battery system with solar panels of higher voltages. MPPT controllers are better suited for larger and more complex solar panel systems than PWM controllers. 

These controllers can track the maximum power point of the solar panel and can work with any solar panel configuration. Specifically, an MPPT controller can: 

  • Keep solar panels at the ideal voltage and current for maximum output 
  • Keep a suitable charging voltage for the battery system

An MPPT controller can provide an extra 10% to 30% more power output than a PWM controller. However, these controllers come at a higher price, and installation may be more complex. 

3. Simple 1- or 2-Stage Controls

Simple 1- or 2-Stage Controls

These charge controllers use relays to control the voltage in one or two steps. These are the oldest types of controllers and are extremely basic compared to the other two types. A simple 1- or 2-stage controller shorts the solar panel when a specific voltage is reached. Although they’re not as efficient as the others, their affordability and reliability through time still attract some solar system owners. 


Why Do You Need Solar Charge Controllers? 

Solar charge controllers are crucial in operating and protecting solar panel systems. But, their necessity depends on the type of solar setup in use.

For grid-connected systems, a solar charge controller is unnecessary. Excess electricity generated by solar panels is automatically sent to the grid. This acts as a natural storage solution. Moreover, it eliminates the risk of battery overcharging or panel damage. It makes the grid a “virtual” charge controller.

Off-grid setups relying on batteries need a charge controller, regardless of their size. The primary function of a charge controller in such systems is to safeguard solar panels and batteries from overcharging. This can harm batteries or shorten their lifespan. It regulates the flow of electricity from panels to batteries. This ensures optimal charging without overcharging.

A solar charge controller is indispensable for off-grid systems with battery banks. Hence, it serves as a crucial protector that enables reliable off-grid power.



Solar panels offer a convenient way to collect and generate energy. But it’s not the only essential component of a solar system. Aside from the panels, battery, and others, a solar charge controller is also important. These controllers make sure that the panels and batteries work properly without overcharging. If you use an off-grid solar system, you need your charge controller. 

If you want to look at some options, you can check out our vast collection of solar charge controllers. We offer all types of controllers from high-quality brands for every system needs!