What Is a Solar Charge Controller & Why Is It Important?

Renewable solar energy is becoming a trend in the country. Many households are already using photovoltaic modules to meet their energy needs. But finding the installer company and arranging to install a solar structure is not enough. To properly operate a solar station, it is important to understand some of the design features of the installation. One of these important elements is the charge controller for solar panels.

Do all solar projects need this detail? What is a charge controller for solar panels, and what device types are there? The answers are in the article’s material.

Who Uses a Solar Charge Controller?

First, you need to designate what is a charge controller. The device that prevents solar panels from overcharging is called a charge controller. Each battery is manufactured to a specific voltage; if exceeded, this will damage the battery and cause it to lose functionality.

To prevent overload, a charge regulator for solar panels is in use. It acts as a gateway between the energy coming from the solar array and the battery storage system. The controllers are a guarantee that the energy storage system will not be overcharged or damaged.

The widespread use of solar voltage controllers does not apply to solar installations. Regulators are necessary only in some cases:

• When installing an autonomous solar station.
• If continuous charging solar panels with a power of 1 to 5 watts are in use.
• In batteries with little maintenance.

The basic rule about using a solar load controller is that if the panel power is up to 2 W / 50 Ah, then there is no need for a device. Suppose the owner has not completely disconnected from the utility grid. In that case, there is no point in buying a controller: excess energy will be redirected to the network, and battery overload will be excluded.

Most solar installations mounted on rooftops or ground structures with battery backup are connected to the grid. If you need to install an autonomous solar station of any size, you cannot do without a solar charge controller ethernet.

Solar Charge Controllers: How Do They Work?

The functions of the solar charge controller are very simple. Controller:

• Blocks reverse current
• Prevents battery overcharging
• Reflects energy flow and battery status (if equipped with a monitor)

Source: Elprocus

The working principle of the solar panel voltage controller is to detect and monitor the voltage level in the battery and precisely regulate the current flowing from the PV modules to the battery. 

There are three steps to recharge the battery:

• Bulk or volumetric: When the battery is low, the solar charge controller transfers much power to the battery for fast charging, up to about 80%.
• Absorption: If the charge approaches the maximum, the controller reduces the current flow so that the battery charges more slowly until it reaches 90%.
• Floating: When the battery is fully charged, the controller maintains a “jet” charge and reduces the output voltage to maintain a full charge until use.

This principle of operation of the solar panels’ charge controller was developed for lead-acid type deep cycle batteries. If a lithium battery is used in the solar system, the regulator can pass a high current until it charges.

Most Charge Controller Types

Having figured out how a solar charge controller works, it is worth moving on to the device types.  The smallest charging controls are 4.5A, and the programmable 60-80A and optionally equipped with a computer interface. Among the control elements, PV charge controllers from 4 to 60 A are more popular.

If the choice falls on autonomous solar energy and there is a disconnection from the grid, you need to choose between three main types:

• 1 and 2-stage regulators
• PWM
• MPPT

Each type of charge controller for solar has its characteristics. To monitor the charge, the controllers have LED indicators or counters that show the voltage in the battery, the current coming from the modules, and the load consumed by the terminals.

1 & 2-Stage Controllers

To control the voltage in 1 or 2 steps, shunt transistors or relays are used in this kind of charge controller for solar panels. When the battery level reaches a maximum, the regulator short-circuits and turns off the solar module.

This type of regulator is rarely in use. However, you might find it in old-style solar installations. Considering how a solar charge controller works, it is the cheapest option in terms of price and inefficient. Its only advantage is the minimum number of components, which reduces the risk of breakage.

Pulse Width Modulation (PWM)

A PWM controller is used mostly in the solar panel with a built-in charge controller. The cost of this type of device is also small – from 20 to 125 dollars, and that’s the cheapest controller among automatic charge controls between batteries and solar panels.

A PWM controller in the solar system guarantees that the battery charge will not exceed the maximum allowable voltage. The regulator turns on and off the energy flow a couple of hundred times per second, which reduces the average voltage of the current coming from the photovoltaic panels. Here are some examples:

• From the solar module to the solar charge controller ethernet receives a charge of 18 W.
• The regulator adjusts the pulses to turn on 82% of the time and turn off 18%.
• Such actions lead to a decrease in the average voltage by 18% or 14.8 W.
• In this sequence of pulses, the battery is half charged; when the charge level is already beginning to approach full, the PWM controller shortens the pulses, for example, by 77% (13.4 W), which prevents the battery from overcharging.

The efficiency of this type of controller is up to 80%. The reason for this indicator is the loss of solar energy to reduce the output voltage.

Features of PWM controllers are the following:

• They gradually reduce the amount of energy that goes to the battery.
• When the battery is fully charged, PWM technology continuously delivers small pulses of energy to maintain a full charge.
• When using a PWM-load controller solar, the solar panel and the battery will have the same voltage (if the solar panel design is small).

The disadvantage of 3-stage solar panel battery charge controllers is that they are only used if the nominal voltage in the solar modules matches the battery voltage. Another caveat – PWM controllers are suitable for use in warm and hot climates.

A PWM version of the controller is suitable for small autonomous solar stations, where several photovoltaic modules and a pair of batteries are connected. If the solar installation has a more impressive size and power output, it is better to use another type of charge controller – MPPT.

Features of MPPT

MPPT is one of the most expensive types of the charge controller. They often come with LCDs and Bluetooth connectivity. They, like PWM regulators, protect batteries from overcharging and reduce the power of energy when it approaches the storage tank.

Source: Victron Energy

MPPT stands for Maximum PowerPoint Tracking. Regulators of this type meet the highest quality standards. MPPT solar charge regulators start at $28 to $350. Compared to MPPT PWM controllers:

• It doesn’t matter if the input voltage from the solar modules matches the voltage of the batteries.
• They adjust their input to get maximum power from the panel.
• They can change the input power depending on the allowable voltage of the connected battery.

These features indicate the greater efficiency of MPPT controllers than the two previous types. The efficiency of the MPRT regulator is from 94 to 98%, which exceeds the similar indicators of 1, 2, and 3-stage controllers from 10 to 30%. Another advantage of MPPT devices is the ability to work in any climate.

Typical Charge Controller Features and Settings

Having figured out what is a solar charge controller and what varieties it comes in, you can move on to the typical functions of the device. Regardless of the type of regulator, all actions are aimed at reaching the following goals:

• Charge support: Even when the batteries are not in use, the controller maintains a charge to be ready for use if necessary.
• Overcharge Prevention: When solar panels generate power, current flows into the batteries even after sunset, and the regulator does not allow overcharging.
• Blocking of reverse currents: The controller can block the flow of electricity between solar modules and batteries (at night, the device blocks the outflow of energy from the battery to the panel, and during the day, it doesn’t allow excess energy to flow into the battery).

It’s also important to understand how to program solar charge controllers. On the regulators, you can set the voltage indicator, upon reaching which the charge rate will change. With the ideal setting of this parameter, there will be some compromise between a moderate recharge of the battery and a fast charge before the end of daylight hours.

Source: Amazon

The controller settings must consider the controller model, battery type, and temperature for the solar panel with a built-in charge controller to work effectively. Temperature sensors in controllers come in several varieties, and here are some of them:

• Some regulators already have a temperature sensor built in: It is suitable for installation in places where the temperature is similar to the batteries.
• In the best models of controls, the temperature sensors are remote: They are connected to the battery and controller via a small cable.
• The alternative option for automatic controllers: It implies the manual adjustment of setpoints. Enough to adjust the temperature twice a year – in spring and autumn.

Another type of controller setting is voltage regulation in batteries of various types. If wet batteries are used, the standard voltage is intended for them. With sealed “maintenance-free” batteries, the allowable voltage indicator must be reduced slightly.

The main rule is that you cannot use a controller unsuitable for a particular type of battery.

How To Choose the Right Type of Controller

You must know how to use the solar charge controller and choose the right element type. It depends on the following factors:

• Panel Types: 12V panels work well with PWM controllers; 24V will require an MPPT.
• Dimensions of solar installation: PWM is ideal for small solar power plants, and MPPT is suitable for large ones.
• Expected Temperatures: At lower temperatures, MPPT performs better;
• Budget: MPPT is more expensive than PWM but also more efficient.

It is up to the consumer to decide which type of controller to purchase to control the current from solar charge, but it is better to consult with a specialist not to harm either the panels or the battery.