What Kind of Charge Controller Does My Solar Panel System Need?

Setting up charge controllers to your solar panel system requires far more planning and equipment than simply plugging all of your solar panels directly into your household electronics. You need the proper tools to help transport, store, and use the electricity your panels generate.

Charge controllers are one of the most important pieces to your solar panel setup, and knowing how to select the right one can feel daunting at first. Luckily, knowledge is half the battle! This guide will explain all of the basics you’ll need to start searching for a charge controller perfect for you.

WHAT IS A CHARGE CONTROLLER?

A charge controller does exactly what the name suggests: it controls the amount of electricity that flows from the device. The charge controller takes the electricity produced by your solar array and sends it to your battery storage.

The main job of a charge controller is to limit how much electricity can go in or out of the batteries or appliances. It is an essential part of your solar setup because it keeps your batteries and appliances safe and continuously charging, while also simplifying and optimizing the battery charging process for you. 

HOW DOES IT PROTECT MY BATTERIES?

Batteries can be damaged if they are overcharged or undercharged so, if your battery is going to be overcharged, the charge controller regulates how much energy goes in. A charge controller only gives enough to keep your batteries topped off. If a battery is going to be over drained, the controller cuts off the battery’s connection to your electronics, keeping the batteries at a 50% capacity to prevent damage.

When your solar panels refill the battery bank to a higher level, the controller will automatically reconnect your electronics to the batteries to be used again freely.

Charge controllers also act as a safety measure for reverse currents. Electricity doesn’t always want to flow one way, and the current may try to flow back into your solar array whenever it can. The charge controller stops this, only allowing electricity to flow from your solar array to your battery bank and preventing damage to the system.

To put it simply, the charge controller works day and night to keep your batteries charged, safe, and long-lasting.

WHAT KINDS OF CONTROLLERS ARE THERE?

The market has tons of different options for charge controllers varying in size, shape, and price. There are two major styles of charge controllers used in the market today:

PWM (Pulse Width Modulation)

MPPT (Maximum Power Point Tracker).

I DON’T KNOW WHAT THAT MEANS!

That’s okay, it looks scarier than it actually is, I promise.

Basically, a PWM is a charge controller in the simplest of terms, literally turning on and off the current going into your battery. PWM does the job to a tee, cutting off the current when the battery is full, and trickling electricity in.

Think of the PWM as a “bare-bones” version of a charge controller. It’s older, it doesn’t limit the output of the current coming from the solar array and can only be used with battery banks matching the voltage of the solar array. Despte that, the PWM is still cheaper and will protect your system just fine.

An MPPT, on the other hand, is a modern and more advanced charge controller. Along with the basic charge controller features, the MPPT makes calculations and conversions to get as much as possible out of your solar array. It does this by converting all of the extra voltage generated by your array into amps. This increases efficiency since you’re getting more electricity into your battery bank, thereby charging it faster.

On average, an MPPT can produce 15 to 30 percent more electricity than a PWM. The MPPT is not limited to matching the solar array’s or battery bank’s voltage, giving you more flexibility in your initial selection of panels and batteries.

If you want a deeper dive, check out this article about designing your solar panels system.

WHICH ONE SHOULD I GET?

Deciding what to get depends on quite a few factors: your setup, your budget, your total watt usage, your location, or even how far away your setup is from your home makes a difference in the selection process.

MPPTs are more common for solar charge controllers and are more flexible to work with. They also giving you a boost in efficiency.

Since PWMs are the older models and are generally cheaper, they only work best in certain scenarios. For example, smaller setups work well with PWMs since the loss in voltage isn’t too much overall. Living in a location with lots of sun and having your battery bank very close to your panels also means a PWM would be a more accessible option. 

PWMs are usually only compatible with solar arrays connected in parallel. Wiring your panels in parallel is an option for smaller systems, but larger and widely-spaced systems usually run panels in a series.

Wiring in parallel increases your total amps, while wiring in a series increases your total volts. Wires used in a parallel system have to be very large since the amperage is so much higher, and the further your battery bank is from your solar array, the more expensive your wires will be, adding to your initial setup bill.

The wires for series are much smaller and cheaper. You’ll likely save time, effort, and money with an MPPT.

It’s safe to say,there is no “one size fits all,” it entirely depends on what your system needs. Ask yourself questions like:

How many panels am I using?

Do I know how many volts are being transferred?

Is my battery bank big enough?

What total PV wattage does the controller need to handle?

For example

If your solar array produces 12 volts and 20 amps, you need a controller that handles more than that. You can’t have it cover volts but not amps. You also need to consider total watts (volts x amps).

Charge controllers have limits on how many watts they can safely transfer to your batteries. You need to:

Calculate your maximum panel output (total watts)

Plan how your setup will transfer that power (series or parallel)

Find which charge controller will fit the job.

For more information on calculating, check our guide here and our solar calculator here.

Always leave some room, and select a charge controller at least 25 percent larger than your maximum output. Otherwise, your system is always at risk, and any deviation above could cause overheating or electric problems. This is a safety hazard, and a fire waiting to happen.

WHAT OTHER FEATURES CAN THEY HAVE?

All charge controllers can have a variety of features, depending on what you want. This can include a visual monitor or Bluetooth connection to observe the charge controller’s efficiency and other similar stats.

You could add a system feature allowing you to charge batteries with a higher voltage than the panels. Even simple things like having extra ports for larger systems are a possibility.

WHAT IF I STILL DON’T KNOW FOR SURE?

You might still have questions on which controller is best for your potential setup. Fortunately, we have experts dedicated to helping you find the best fit for whatever solar setup you’re planning.

Check out our website for product options, professional advice, and more! We also have plenty of other blogs that can help you with all things solar, so if you’re looking for information and help, please check them out here!