MPPT vs PWM Charge Controllers: What's the Difference?

In this article, we will introduce: how do MPPT and PWM work, what is the difference between MPPT and PWM? and give some examples to make it easier for you to understand. But before that, we will briefly introduce solar usage trends, benefit and characteristics and solar charge controller, let's get started!

As we all know, we could harness the sun’s energy and convert it to electricity by using Photovoltaic Panels or simply Solar Panels. One of the most common ways that an individual can contribute to reducing the carbon footprint in the environment is by conserving the consumption of electricity and switching to renewable energy.  The use of solar energy is a good thing because it is free and unlimited as it comes from the sun.

Did you know that the energy coming from the sun is labeled as the energy of the future? The International Energy Agency said that solar energy significantly contributes to finding solutions to the most common environmental problems like climate change and energy security. Just considering the American household, about 5 metric tons of carbon dioxide emissions were lessened when they started to use solar energy in providing electricity to their homes. In 2019, carbon dioxide emissions increase to 70 million metric tons annually, equating to planting 1.2 billion trees. That is why the use of solar energy has become evident throughout different countries in the world and with the advancement of technologies and creative minds, not just businesses and companies have gone solar but even residential houses! It may require you to invest quite a cost, but it is truly worth it because it is environment-friendly and will save you from paying electric bills.

The non-renewable resources are now unstable, and no one is certain of their availability. In the long run, utilizing the energy that the sun gives us is a good source of power. So how do you convert solar energy to be used as electricity in a simple household? The basic process would be using one or more solar panels which, when the sun hits the panel, energy is transformed into DC, and is then converted to AC energy using an inverter. The AC energy can now be supplied to the household since the widely used type of energy of a common household device is in AC form. This is how a photovoltaic system works.

There are a lot of things to consider before installing solar panels especially when you are going to have a DIY project. From the structure of a building or a house, costs, environmental factors, and the solar panel itself. One significant thing to take into consideration is choosing your solar charge controllers. How does it work, and do you need one in your solar system setup? In this article, we will go through everything you need to know about solar charge controllers and their variations. So, if you are currently planning to go solar, then this might be a help!

What are solar charge controllers?

A photovoltaic system is not a perfect system. The sun’s energy could be varied depending on your location. The weather condition also has a huge impact on your system due to the different weather and seasons that you have. One example of a device that can help you maximize solar energy is a solar charge controller. It is a device that is connected between your solar panel and battery storage.

For better understanding and easy reading, let us first define solar charge controllers. Solar charge controllers are one of the important components to have in solar power installation. It is a device that limits energy flow from the solar panels to the batteries to protect them from overcharging and over-discharging. It also keeps the batteries from any damage which can be used for a longer time. In short, it is a charge regulator that protects the batteries from a solar panel by regulating its energy flow. Solar charge controllers have different features, it contains reverse current protection that prevents the panels from discharging the batteries during nighttime, during the absence of sunlight.

Solar charge controllers are categorized into two types. These are the MPPT and PWM charge controllers which we will further differentiate in the next topic. There is a variety of manufacturers that can be found online, and the cost of this device depends on its classification but you can get one for as low as $70.

Imagine having no solar charge controllers installed, the regulation of the energy from the solar panel to the batteries will be out of control and may damage the battery or the solar power system itself. Nevertheless, the use of solar charge controllers is not always required. It still depends on the solar setup that you have, and you can identify it by using a Mathematical equation! All you must do is get the quotient of the battery amp hour capacity and the solar panel maximum power amp rating. If you get above 200, then a controller is not needed. But if it’s less than 200, you would need a solar charge controller.

You can also get the maximum power from your solar panel by the relationship between the voltage and current of your controller by using the formula Power = (Voltage x Current).

What to consider when choosing a charger controller?

• Price;
• Your energy needs and number of solar panels;
• Battery type and voltage;
• The place your solar system installed;

Different types of charge controllers (MPPT vs PWM)

There are two types of solar charge controllers, these are the MPPT and PWM. They do the same job which is to regulate charge from the panel to the batteries, but they differ when it comes to function, advantages, disadvantages, and cost. In this part of the article, each type will be defined and discussed when it is most appropriate to use MPPT or PWM.

What is MPPT?

MPPT is short for Maximum Power Point Tracker, it was founded by Stuart Watkinson, from a small Australian Energy, and was first used in 1985. The key feature of an MPPT is it has two different kinds of circuits inside that is why it is described as a charge controller that uses DC to DC converter.

It also guarantees that your solar power system is always functioning at its best despite any conditions in your surroundings.

It is said that, normally, having two MPPTs is better than having one because dual MPPTs give a greater system design. Having too much wiring works in your setup can be inefficient and sometimes may lead you to an unsafe situation. The use of dual MPPT is it can connect panels that are placed on different tilted angles and wiring lengths.

The MPPT is quite more intelligent than the PWM. It has better performance under any circumstances compared to the PWM which has only limited functions, but it does not make the PWM irrelevant when it comes to playing its role in the solar power system. It is commonly used in large solar power installments that have large panels with up to 400 watts. It is best functional in cold places or during cold weather because this is the time when there are few sun hours, and you need to charge batteries most of the time.  

Furthermore, MPPT solar charge controllers use the Vmp rating of the solar panels (which is usually higher than the rated voltage of the Panels) and down-convert it to a suitable voltage to charge your batteries, it raises the current to charge the batteries faster, opening a whole wide range of solar panels that now can be used for your off-grid solar system or your portable solar generator.

Example: With the Growatt INFINITY 1500, the maximum W input is 800W and a maximum PV input of 120V, which means that you can connect 4 x 200W Growatt solar panels in series to charge the batteries.

A great example of a portable solar generator that supports MPPT charging is the Growatt INFINITY 1500. It has a maximum Wattage rating of 800 Watts and a battery capacity of 1,512 Watt-hours of run time. Furthermore, it can support 4 x 200-Watt Growatt solar panels which provide a high conversion efficiency of 22%, and with leading 99% MPPT efficiency. Since it uses MPPT charging, the Growatt INFINITY 1500 can accommodate a higher number of solar panels and can be fully charged in just about 2.5 hours.

What is PWM?

Now, let us talk about the PWM or the Pulse width modulation. It is a type of solar charge controller that connects the solar panels and the battery. It just simply uses an “ON and OFF switch” to regulate the charging of the battery. The switch is on until the battery reaches its maximum level of charge without overheating, then it will start to on and off rapidly to regulate the current and maintain a constant battery voltage.

Since the energy that we can harness from the sun differs depending on the amount of sunlight, the voltage and current output of the panel also differs making irregular fluctuations. In this case, the MPPT solar generator can accommodate these variations by controlling the output voltage and current to produce its maximum power. Unlike the PWM controller, it only acts as a switch that can be turned on using a fixed voltage and current depending on its design. In this case, the solar input voltage must match the battery bank voltage which is why it is not suitable to have more solar panels connected.

To further differentiate the MPPT and PWM functions, below is the comparison of how an MPPT charge controller is more efficient than a PWM controller. As I’ve mentioned above, to get the maximum power of your panel you must consider the voltage and current capacity of your controller. Given the example below, if you use a PWM controller designed with 12V operating voltage and 8A current, by using the formula Power = (Voltage x Current) the output of your system power would be 96W. Since an MPPT generator can control its voltage and current, in the figure below it can regulate 12V the raises the amperage to 20.8 A which can produce 249.6W. This is equivalent to 99% of the designed output of your solar panels.

Pros and cons of PWM and MPPT?

MPPT has better features, is advanced, and is more efficient than the PWM so it is expected to be up to five times more expensive. If you are opting for a budget-wise while still serving its function, then you must make use of the PWM. Being a solar charge controller at a low cost does not make it low quality, it’s just that it provides us with simpler features.

The size of your solar power system installment is a huge factor in choosing what charge control is for you to use. MPPTs are most likely to use in professional applications while the PWM charge controller best works in smaller solar setups like solar-powered lights and some electric motors. When the conversion efficiency is the main concern, then you should choose the MPPT charge controller because it has a 95% efficiency compared to the PWM which has only about 75%. PWM charge controllers can also be appropriate in solar setups that have 300-400 watts or less.

MPPTs would not require you to do a lot of wiring work unlike in PWM. This technology can also be utilized for outdoor activities such as camping or fishing which have a limited source of electricity. Bringing an external source of electricity can be a huge help in providing a comfortable leisure time, given the location and condition of the environment.

Comparison Table of MPPTvs PWM

Conclusion

Now that we learned that the essential component of your solar power system is the solar charge controller, it would be better and more efficient to have it. There are two main types of charge controllers, the Maximum Power Point Tracking (MPPT) and the Pulse-width Modulation (PWM). These two have their different roles, depending on the circumstances, and learning about them would help you on what type of charge controller you must have.

Switching to the use of renewable energy, particularly solar energy, provides us with a lot of benefits. It’s like having a give-and-take relationship with the environment. Carbon footprints are reduced, and Mother Earth is happy! Who would not want to inhale healthy and clean air, right? The use of solar energy may sound easy, but it would require you to do a lot of research, and seeking advice from a professional in this field would also help. Expressing your solar ideas through innovations and DIY projects is a good thing but always keep in mind that it is important to learn about the appropriate equipment to use and to consider the conditions of your surroundings. Being serious about having your solar power system does not just require you to put a lot of money into it, you also need to give much interest in the components and their functions.

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