The Ultimate Guide to Solar Charge Controllers:

MPPT and PWM Charge Controllers

Charge controllers are some of the most misunderstood components of solar installations. But it doesn’t have to be that way. In short, solar charge controllers sit between the solar panels and the batteries or inverters to regulate the amount of energy flowing from the solar panels. This makes them essential from a safety and efficiency standpoint.

There’s a few things to consider when shopping for solar charge controllers, including type and capacity, so you’ll also want to take the time to properly size your system to determine your energy needs. Additionally, your budget, climate where the system will be installed, how many solar panels you have, and your expected lifespan are all other factors to take into account.

In this guide, we talk about the basics of solar charge controllers, knowing the difference between PWM or MPPT controllers, and what to look for when shopping for charge controllers from Renogy.

What are solar charge controllers?

Charge controllers serve the important function of regulating the flow of energy collected from the solar panels and stored into the batteries. This is a safety feature and also preserves the life of batteries. Many people like to think of charge controllers as the gatekeeper or regulator for the system. They serve the following purposes: overload protection, low voltage disconnects, and block reverse currents.

Overload protection: If the current flowing into your batteries is much higher than what the circuit can deal with, your system may overload. This can lead to overheating and cause fires. Charge controllers prevent this from happening.

Low voltage disconnects: Charge controllers have an automatic disconnect of non-critical loads from the battery when the voltage falls below a predefined threshold.

Block Reverse Currents: Solar panels pump current through your battery in one direction. At night, panels may naturally pass some of that current in the reverse direction without a charge controller to limit this. This can cause a slight battery discharge. Charge controllers prevent this from happening by acting as a valve.

And just like solar panels, there’s not a one-size-fits-all charge controller, so it’s important to understand how they work, what functions they serve, and what’s available in the marketplace.

In this section, you’ll learn more about the nitty gritty of charge controllers and how they work.

Selecting a solar charge controller

Charge controllers come into two main forms: Pulse Width Modulation (PWM) and Maximum Power Point Tracking (MPPT) controllers. PWM charge controllers are an older technology and are cheaper, but are also less efficient than MPPT charge controllers. Also, it’s important to point out that it’s not a matter of which is best all-around, but often what is best for your unique case.

Are you living in a remote cabin? An RV? In a hot climate? All these things will impact which solar charge controller should be purchased.

Also, we highly recommend purchasing a high quality charge controller since controllers only account for a small portion of the total system cost. Read the following posts to learn more about the specifics of these charge controllers and what makes them unique.

Solar charge controllers at Renogy

Renogy has a range of solar charge controllers available for purchase. They’re available in both PWM AND MPPT options, as well as in varying amp readings of 10 to 60 amps. Charge controllers are rated and sized depending on your solar array's current and the solar system’s voltage. You typically want to make sure you have a charge controller that is large enough to handle the amount of power and current produced by your panels.

When it comes to charge controller sizing, you also have to take into consideration whether you’re using a PWM or MPPT controller. MPPT controllers limit their output, so you can make an array as large as you want and your controller will limit that. However, this means your system isn’t as efficient as it could be. Even if your panels have the potential to produce 80 amps of current, a 40 amp MPPT charge controller will only produce 40A of current, no matter what.

PWM controllers are unable to limit their current output. They simply use the array current. Therefore, if the solar array can produce 40A of current and the charge controller you’re using is only rated to 30A, then the controller could be damaged. It’s crucial to ensure your charge controller is matched, compatible with, and properly sized for your panels. Review some of Renogy’s bestselling charge controllers below.

Put it all together

Charge controllers may be confusing at first, but hopefully by now you have a better understanding of both the crucial functions of charge controllers, as well as what might be the best controller for you. These gatekeepers of solar installations serve an important role in creating a safe and effective system, and we wish you all the luck!