Are MPPT charge controllers the best option for my solar installation?

Charge controller technology has advanced greatly over the past decade, making it possible for more individuals to have powerful, affordable, and efficient charge controllers for their solar installations. Maximum Power Point Tracking (MPPT) charge controllers are some of the most popular controllers available and keep your solar installation running safely and efficiently and ensure your batteries are supplied with a steady and optimum level of power.

What is an MPPT Charge Controller?

Maximum Power Point Tracking (MPPT) charge controllers are highly efficient at using the full power of your solar panels to charge your batteries. MPPT charge controllers perform the important function of limiting the output from your solar panels to your batteries to ensure your battery bank doesn’t get overcharged and subsequently damaged. They convert the higher voltage DC output from solar panels down to the lower voltage needed to charge batteries. Essentially, they actively monitor and adjust their input to regulate your solar system’s current. The overall output will increase as a result and you can expect efficiency ratings of 90% or higher. 

What are the differences between MPPT and PWM charge controllers?

PWM controllers are the other main controller technology available in the market and are suitable for smaller systems or where efficiency isn’t very important. The main difference between the two is that PWM controllers are much simper and draw the current from the solar panels at just above the voltage of the battery.

An MPPT controller draws the current from the panel at the maximum power voltage. You can think of an MPPT controller as a“smart DC-DC converter.” Like a regular DC-DC converter, the current is increased in the same ratio as the voltage is dropped. A MPPT charge controller will monitor the maximum power point of the panel, which varies throughout the day due to sun intensity, angle, shading, and panel health.

What are the pros and cons of MPPT solar charge controllers?

Pros:

• Highly efficient due to actively monitoring conditions
• Perform better if you’re in cold, cloudy environments
• Suitable for larger systems where the additional energy production is valuable
• Perform best when the battery is in a low state of charge
• Ideal in situations where the solar array voltage is higher than the battery voltage

Cons:

• More expensive than PWM controllers and cost between about AU$100 and $500. PWM controllers can cost as little as about AU$30.
• Tend to have a shorter lifespan due to more components present in the technology.

What are the limitations of MPPT charge controllers?

Because MPPT controllers limit their output, you can build an array as large as you want and a controller will limit that output. However, this means your system isn’t as efficient as it could be since you have panels that aren’t being properly utilized. All MPPT controllers have an amp reading, for example a 40 amp MPPT Controller. Even if your panels have the potential to produce 80A of current, a 40 amp MPPT charge controller will only produce 40A of current, no matter what.

Where can I mount the charge controller? 

Excess voltage will be converted into heat and dissipated into air. Therefore, it’s crucial that you keep your charge controller mounted in a well-ventilated space with at least 9 inches of clearance around the charge controller.

How should I wire my panels with an MPPT charge controller? Your solar panels can be wired either in series or parallel or combination of series/parallel using MPPT charge controller. This makes MPPT charge controllers a highly versatile component.

Do I need a charge controller in every solar application?

You will typically need a charge controller in most household or caravan applications. You don’t need a charge controller with small 1 to 5 watt panels. If a panel puts out 2 watts or fewer for each 50 battery amp hours, you probably don’t need a charge controller. Anything above that and you do.

How to size your charge controller?

Overall, charge controller sizing is not as difficult as you may think. When it comes to charge controller sizing, you should first take into consideration whether you’re using a PWM or MPPT controller. An improperly selected charge controller can result in up to a 50% loss of the solar generated power.

If your solar system's volts are 12 and your amps are 14, you would need to install a solar charge controller that is at least 14 amps. However, due to factors such as light reflection, sporadic increased current levels can occur, you need to factor in an additional 25%, bringing the minimum amps that your solar charger controller must have to 17.5 amps. We’ll round up in this case. In the end, you would need to purchase a 12 volt, 20 amp solar charge controller to meet the needs of your solar installation.

How do I know what size system I need?

To determine what size system will best fit your needs, make a list of all the appliances and devices you plan on running. We recommend using the Renogy solar panel calculator to properly design a solar installation that will meet your energy needs. You’ll need to know what total watts your electronics will consume, how long you plan on running devices, your charge controller efficiency, and average sun hours per day.

Conclusion

With more and more households adopting smart technology, from thermostats to lighting, investing in an MPPT charge controller is a great way to make your solar installation just as smart. MPPT charge controllers are highly efficient at using the full power of your solar panels to quickly and safely charge your batteries. By actively monitoring and adjusting their input to regulate your solar system’s current, you’ll be able to see increased solar system efficiency and output. In short, MPPT controllers are a wise option for many households looking to be smart, green, and efficient.