The easiest way to identify PWM and MPPT solar controller

In the solar street light system, the control center is the solar controller (solar charger), which controls the charging and discharging and turns on/off the solar street light.

According to the different charging ways, we divide the controller into PWM controller and MPPT controller. So what's the difference?

In this article, we will show you:
What's the biggest difference between PWM and MPPT controllers?
How to calculate the charge efficiency of PWM and MPPT controller in an easy way?
How to choose the right solar controller for your lighting system?
How to identify if you have bought a real MPPT controller?

1. What's the biggest difference of PWM and MPPT controller?

The different charging ways lead to different charging efficiency, this is the biggest difference between PWM and MPPT solar controllers.

PWM controller:

PWM controller provides a constant voltage output, so when the charge current is limited, the solar panel can not charge the battery at full power. This is a traditional charging way and is widely used in the market. However, due to the constant voltage output, in most cases, the solar panel can not work at the optimal efficiency, and the charging efficiency is low.

MPPT controller:

MPPT is short for Maximum Power Point Tracking. It is a digital electronic tracking. The charge controller can figure out what is the biggest power that the solar panel can put out to charge the battery in real-time, so the MPPT controllers' efficiency is up to 96%.

2. How to calculate the charge efficiency of PWM and MPPT controller in an easy way?

We suppose it is noon and the sun is very strong. At that moment, the power of the solar panel can reach 100w.

If using a PWM controller, since it provides a constant voltage output, the calculate as below:

Solar Panel charge current: 100W/18V=5.55A
Battery charge current: 5.55A
Battery charge power: 12V*5.55A=66.6W
Solar panel charge efficiency: 66.6/100=66.6%.

In the real charging situation, the battery voltage may be 11V-14.2V, so the charging efficiency may be 61%-79%.

If using an MPPT controller, considering the tracking efficiency is 96%, the battery charge power will be 96w. The calculate as below:

Solar Panel charge current: 100W/18V=5.55A
Battery charge current: 96W/12V=8A
Solar panel charge efficiency: 96/100=96%.

It is clear that the MPPT controller has a higher charge efficiency.

Absolutely, we do the calculation in an ideal state. In fact, since the MPPT controller will generate more heat in the process of working, and high temperature will decrease its tracking efficiency, it will not have such a high efficiency in the actual process.

But generally, in winter, the efficiency of MPPT will be 20%-30% higher than the PWM; in summer, the efficiency will be about 10-15% higher.

3.How to choose the right solar controller for your lighting system?

So which controller we should choose for our solar street light？ The MPPT controller is always the best for your solar lighting system?

Absolutely not, we should choose the right controller based on price and working environment.

a. Consider the Price and the power of the solar panel
If the solar panel is less than 100w, choose a PWM controller but buying a 110-120w solar panel will save more money and the system will work better. If the solar panel is larger than 120w, using an MPPT controller will more cost-effective.

b. Consider the working environment
The MPPT controller has a large working current, and it always tracking in the process, so it generates more heat. In order to protect the controller from being damaged due to overheating, the controller is equipped with temperature protection. If the temperature is too high, the charging of the controller will be limited, and the charging efficiency will be reduced. This is why MPPT charging efficiency is high in winter and low in summer. So if the working environment temperature of the controller is high and the heat dissipation is not good, a PWM controller will work better.

That's the reason why the PWM controller works better than the MPPT controller in the two-in-one solar street light.

4. How to identify if you have bought a real MPPT controller?

We have calculated the charging efficiency in part two, we can see that the charging current of the battery is different when we choose a different controller.

Use the PWM controller, the charge current on the solar panel and battery is almost the same.

But using an MPPT controller, the battery charge current is larger than the solar panel charge current.

So the easiest way to identify the controller type is by testing the charge current.

If you have more questions about how to choose a solar controller, you can contact us. Soaring Lighting is a professional solar street light manufacturer. Our engineers have done lots of research on solar panels, batteries, controllers, and LED lights, and have professional testing equipment to do further analysis. We sure can provide you with more support.

Sales department: sales@soaringlighting.com
Tech department: tech@soaringlighting.com