Solar Charge Controller – How to Choose the Correct Option?

Short on Time? Here’s The Article Summary

The article discusses the importance of a solar charge controller in a solar power system, explaining its role in regulating the current flow to and from the battery bank. It explores two main types of solar charge controllers, PWM and MPPT, detailing their differences and functionalities. The article emphasizes the need for a solar charge controller to prevent overcharging and reverse current flow, which can damage the battery bank. It also highlights key features of a solar charge controller, such as overload protection, low voltage disconnection, and prevention of reverse current issues.

Link to KINGSUN

Additionally, the article provides guidance on sizing a solar charge controller based on the current and voltage of the solar array and battery. It explains the sizing process for both PWM and MPPT controllers, recommending that the controller's capacity should exceed the maximum potential of the solar array to account for environmental factors. Lastly, the article recommends specific PWM and MPPT solar charge controllers for different solar power system setups.

Introduction

Sizing a Solar Charge Controller – How to Choose the Correct Option for Your Solar Power System

A solar charge controller plays a vital role in any solar power system. Essentially, the charge controller is the regulator that limits the rate of current that flows to and from the system’s battery bank. By controlling the flow of energy from your solar panel array, the solar charge controller can prevent overcharging issues and reverse the current flow when the solar panels are not generating electricity.

Despite the fact that the solar charge controller plays such an important role, few people know how to accurately determine the correct unit for their solar power kit.

How Can We Help?

To help you choose the correct solar charge controller for your specific setup, we will explain what function the controller performs and explore the two main types you can choose from. From there, we will go over the basics of charge controller sizing and explain how you can calculate array current and the load current, so you can determine your solar power system’s controller needs for yourself.

Why Do You Need a Solar Charge Controller?

In simple terms, a solar charge controller manages the power flowing into the battery bank from a solar array. They protect the expensive battery bank in a solar power system by preventing overcharging during daylight hours. They also prevent power from flowing backwards to the solar panels at night, which reduces the impact of phantom battery drain.

While some solar charge controllers have additional capabilities, like load control, managing the flow of power is their primary function. If you have invested in a battery bank for solar to store the energy, your system will require a solar charge controller.

What are the Two Types of Solar Charge Controllers?

Solar charge controllers are available in two separate configurations – PWM and MPPT. Understanding the differences between the two will help you determine the best option for the particular needs of your solar power system.

Pulse Width Modulation Charge Controller (PWM):

PWM solar charge controllers tend to be less expensive, as they feature less advanced technology. Essentially, a PWM acts as a simple switch, which turns on and off at set parameters to prevent overcharging issues.

Using a PWM, the solar panel, or panels, need to be at the same voltage as the battery, as you connect them (more solar panel connectors types) directly to the battery with just a switch separating them. Since the type of battery bank you are using will determine the output the solar panels can generate, there is a considerable loss factor, usually in the range of 30%.

Maximum Power Point Tracking Charge Controller (MPPT):

MPPT charge controllers are considered ‘smart’ units, as they feature a built-in computer, which makes them programmable and much more adaptable than PWM controllers. They function by measuring the voltage of the panels and down-convert it to match the voltage of the battery.

Since the power flowing into the battery from the charge controller is dropped to match the battery bank, the current can be raised, which means more of the available power is flowing from the panels to the battery. Basically, you can use a higher voltage solar array than the voltage of the battery, which opens up a wide range of options and allows you to make your solar power system far more effective and even scale it up.

The Key Features of a Solar Charge Controller:

• Overload Protection – Prevent excessive current that exceeds the amount the circuit can handle from flowing into your battery. This prevents overheating issues and the premature deterioration of your battery.
• Low Voltage Disconnection – Automatically disconnects non-critical loads from the battery when the voltage falls below the necessary amount. This prevents over-discharge issues.
• Prevention of Reverse Current Issues – When the solar panels are no longer generating power (usually at night), current can flow in the reverse direction, which means electricity will flow from the battery to the solar array. A charge controller prevents this from happening and prevents the unnecessary loss of power.
• Advanced Features – More advanced MPPT solar charge controllers often feature display screens, which allow users to monitor voltage and charge information. They can also permit multi-stage charging of the battery, meaning they will charge the amount of power sent to the battery based on its charge level, which helps protect the health of the battery.

Solar Charge Controller Sizing:

The first step in sizing your charge controller is determining whether you will be using a PWM or a MPPT controller, as they are sized differently.

Charge controllers are sized based on the current and voltage of your solar array and battery. You will want to choose one that is capable of handling the full current potential of your solar array, which will maximize your system’s efficiency and power potential.

Charge controllers are typically available in 12, 24, and 48 volt varieties. Amperage ratings will range from 1 to 60 amps.

Basically, you just need a charge controller that can handle more than your solar panels can generate. For example, if you use 12v solar panel at 14 amps, you would need a charge controller that could handle at least 14 amps. However, it is a good practice to exceed this minimum, as environmental factors can cause surges and spikes.

Sizing a PWM Charge Controller:

Since they cannot limit their current output, you need to match and preferably exceed the current of your solar panels. When searching for a PWM controller, look for the amperage and voltage rating and make sure these numbers exceed your solar array’s rating and that of your battery.

After you have identified the voltage of your system and found a charge controller that matches or exceeds that value, you need to look at your battery’s rated current. This is where we recommend choosing a charge controller that can exceed the amp rating of your solar array, as it can spike. A good practice is to exceed the amp rating by 25%, which means multiplying the amp rating of your solar panels by 1.25 and finding a charge controller with an amp rating that exceeds that number.

If finding a charge controller that matches and exceeds the nominal voltage of your system, the rated current of your battery, and the maximum solar input seems like a complicated task, do not worry, it is actually fairly straightforward once you have your numbers. However, it is worth noting that the entire process is easier if you opt for an MPPT charge controller.

Sizing a MPPT Charge Controller:

As explained above, MPPT charge controllers regulate output, so they do not need to be matched to the maximum output of the solar array. However, you will still want your MPPT charge controller to exceed the current potential of your solar array, so it can maximize the efficiency of your system.

Since MPPT controllers can lower voltage to match the battery bank’s voltage and increase current to make up for the loss of power, they are far more adaptable.

Want more information on 30 Amp Solar Controller? Feel free to contact us.

You will still want to make sure that your charge controller can allow your system to run as efficiently as possible, so divide the total wattage of the system by the lower voltage value between the solar array and battery. Follow Watts/Volts to determine the amps. So, if you were running a 900W solar array with 48V and your battery’s voltage was 24V, you would divide 900W/24V to get a value of 37.5A. Adding an additional 25% for potential current spikes would give you a total of 46.9A.

This would mean choosing a MPPT charge controller that could handle at least 24V and 50A.

Recommended Solar Charge Controllers:

If you are running a smaller scale solar power system and you are looking for a solid PWM charge controller, we recommend the:

The Zamp Solar - 30A 5-Stage PWM Charge Controller

For those looking for a more advanced option, we recommend the following MPPT solar charge controllers:

Outback Power - FlexMax FM60 MPPT Charge Controller

Victron - SmartSolar 100/50 Bluetooth MPPT Charge Controller

The Ultimate Solar + Storage Blueprint (Mini Course)

Struggling to understand how solar + storage systems actually work? Looking to build or buy your own solar power system one day but not sure what you need? Just looking to learn more about solar, batteries and electricity?

Join 15,000+ solar enthusiasts breaking free from their energy dependence with this short step-by-step video course that will make you a solar + storage expert. Start your journey to energy independence today.

Learn More Now

Who is ShopSolar.com?

Solar charge controllers are an invaluable piece of equipment that help maximize solar output in residential and commercial photovoltaic systems, ensuring effective usage of these forms of renewable energy. In this comprehensive guide, we'll discuss essential basics related to solar charge controllers, such as what they are, how they work, their types, and other information you need to know.

What Is a Solar Charge Controller?

A solar charge controller is an essential element in any solar-powered system, whether it be a home or an RV. This gadget regulates the power flow between the solar panel and the battery, ensuring that the battery remains at a consistent state of charge. 

Since solar panels produce different amounts of electricity depending on factors such as weather conditions, the charge controller ensures that excess power doesn't damage the batteries. Without a charge controller, a solar-powered system wouldn't be able to function optimally, and the batteries would quickly degrade. Besides, a charge controller can prevent overcharging, which will prolong the life of your battery and prevent damage to your system.

How Does a Solar Charge Controller Work?

The solar charge controller works by measuring the voltage of the batteries and the solar panels and adjusting the flow of electricity accordingly. When the batteries are fully charged, the controller will reduce the amount of electricity flowing into the batteries to prevent overcharging. On the other hand, if the batteries have a low charge, the controller will increase the flow of electricity to recharge them. Some controllers can also track the weather and adjust the charging parameters based on the amount of sunlight available, ensuring optimal charging efficiency.

Main 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.

PWM controllers: PWM controllers regulate the voltage from the solar panels to the battery at a fixed rate. They're well-suited for smaller, simpler solar systems and come with a number of useful features, including low cost and low maintenance. However, their functionality is limited to fixed solar panel configurations, and they tend to be less efficient than their MPPT counterparts..

MPPT controllers: MPPT controllers are efficient and versatile, better suited for larger and more complex solar systems. They can track the maximum power point of the solar panel, providing up to 30% more power than a PWM controller, and can work with any type of solar panel configuration. However, their increased performance comes at a higher price point compared to PWM controllers. Despite the price, solar charge products with MPPT controllers are more popular on the market, such as the Anker Solar Generator 757. This generator consists of a Wh-capacity portable power station and three 100W solar panels. The power station features a built-in MPPT solar charger controller, which optimizes the charging process through solar panels for maximum efficiency.

How to Choose the Right Size of Charge Controller?

Solar charge controllers are available in different sizes suitable for solar arrays with varying voltages and currents. Choosing the incorrect size can lead to both power loss and inefficiency. Thus, it's crucial to choose the right size for your solar array, as this will help ensure optimal performance.

• Firstly, you need to check the voltage rating of the charge controller. Typically, PWM controllers are designed to operate with either 12 or 24 volts, whereas MPPT controllers can handle systems with 12, 24, 36, and 48 volts.

• And most charge controllers have an amperage rating. PWM controllers with smaller capacities may be rated at 10, 20, or 30 amps.While MPPT controllers for larger solar arrays, are often rated at higher amperage - typically 80 to 100 amps.

• Then, to calculate the potential amperage output of a solar array, we need to take a simple calculation according to this formula: Amps = Watts / Volts.

• Suppose we have a solar array which provides 800 watts of power while operating at 12 volts. In this case, we could readily calculate the amps output by such an array through the formula: Amps = 800 watts / 12 volts = 66.67 amps.

• Thus, this solar array can produce up to 66.67 amps. Accordingly, it's recommended to use a charge controller rated at 70 amps to avoid overloading and possible malfunction.

Other Things You Need to Know About Solar Charge Controllers

Apart from the above-mentioned information, there are a few other important things you need to know about solar charge controllers if you're planning to use one.

Why Are Displays and Metering Important?

The display provides real-time information about the charging process, the battery voltage, and other crucial parameters. And these information are important in effectively monitoring and managing your solar system. Metering, on the other hand,  measures the amount of energy coming into the solar system from the solar panels. This information enables you to calculate important metrics, such as the system's efficiency and energy consumption.

Control Set Points vs. Temperature

The temperature plays a critical role in battery charging. The charging process is more effective in warm temperatures, where batteries can efficiently conduct energy. On the other hand, low temperatures hinder the battery's ability to distribute energy, resulting in slower charging speeds.

Therefore, most charge controllers have control set points for room temperatures. And to regulate the voltage for various temperatures, most charge controllers feature temperature compensation. What’s more, some charge controllers even support custom control set points based on temperatures.

Common Features and Settings on a Charge Controller

Generally, charge controllers used for residential purposes equip an LCD screen that delivers essential information. And some charge controllers offer the facility for personalized system set points to work cohesively with your battery and climatic conditions. In addition, many charge controllers come with built-in safeguards to protect against various electrical issues like overload, short-circuiting, and reverse polarity.

What’s more, premium controllers with advanced technologies now come equipped with the capability of remote monitoring through smartphones and Bluetooth. Using software like the Anker smart app enables you to manage these features directly from your smartphone with ease.

Conclusion

In conclusion, solar charge controllers are an invaluable tool when it comes to utilizing solar energy efficiently and safely. Whether you’re looking to power your home or your business, this guide will help equip you with the knowledge necessary to make the best choice possible. By taking into account your specific needs and preferences, you can easily find the right type of controller to ensure that your system runs smoothly with the minimum amount of maintenance and cost.

FAQ

Is a Solar Charge Controller Always Necessary?

For off-grid solar installations with batteries, a solar charge controller is always necessary. The only exception is when using very small 1 or 5-watt trickle chargers. Conversely, grid-tied residential systems do not require a charge controller as the utility grid governs the electricity flow and manages the spare power.

Do 100-Watt Solar Panels Require Charge Controller?

If a 100-Watt solar panel is used to power a battery, a solar charge controller is necessary. Some small solar systems include only a single 100-watt panel and a battery. These systems need solar charge controllers to regulate the current entering the battery.

Are Charge Controllers Needed for 7-Watt Solar Panels?

You don't need a charge controller for a 7-watt solar panel. These panels are specifically designed for low-voltage trickle charging, which means you don't have to worry about regulating the electrical flow.

If you are looking for more details, kindly visit Amorphous Solar Panel.