Question. Which controller is better PWM or MPPT?

If all you are doing is charging battery, and you are getting more power than you need from the solar panel(s), it really won't matter at all. A PWM controller just increases the current on the solar panel to try and reach the set charge current. If more than enough energy is coming from the panel, it is just a current limiter. With an MPPT controller, if the panel is also making more power than you need to hit your charge current, again, it just becomes a current limiter. Both need to just throw away the excess power because it is ding it's job of controlling the charge current into the battery.

Now what happens when there is not enough sun on the panel?

The MPPT controller will constantly adjust the current draw on the solar panel, looking for the point where the combination of current and voltage reaches the maximum power. This requires an intelligent search function. As less light is hitting the panel, the available current will fall. With a fixed load, the voltage would also fall. A good MPPT will try adjusting the current, and sometimes a bit less current will allow the voltage to climb up and make more power, other times, pulling more current will make more power, even if the voltage drops some. The controller has to be constantly adjusting and testing the result to know which way it needs to go to get the maximum power.

A PWM controller will just ramp up current until it sees the output current set point. If the panel starts falling short, the controller will just swing to maximum current draw, which essentially ends up just shorting the solar panel straight to the output. You will get a bit less than the short circuit current with the panel being pulled down to the voltage of the battery.

Both controllers should also monitor the battery voltage. As the battery reaches the maximum absorption voltage, they will both again start reducing the current they pull from the solar panel, which in turn will put less current into the battery. The current should fall to the point where the voltage will just stay at the absorb voltage as the battery tops up.

So with full sun and a low charge current, they are the same, and at near full charge, they also act about the same. The big difference is when the batteries can accept more power than the solar panels are producing. In that window, which could be most of the time on a high power system, the MPPT will be able to put much more of the solar panel power into the batteries. You will charge faster with MPPT.

Most controllers either PWM or MPPT only use a switching "buck" converter. They both can reduce the voltage from the panel down to the battery voltage. And in both cases, they will trade off a lower voltage to a higher current. The only real difference is the MPPT having intelligent control to keep adjusting the set point to get the maximum power. Straight PWM does not search, and when the current from the panel falls low, it just keeps trying to pull more current, but the panel can't produce it, so the efficiency goes to crap. This is where you want the solar panel VMP to be close to the battery absorb voltage. With that setup, the poor PWM just defaults to putting the solar panel straight to the battery, and the loss is not too bad. Where with an MPPT controller, you can easilly use much higher voltage, run smaller wire, and the smart current search will run the "Buck" regulator at the proper duty cycle to reduce the VMP of the panel to the battery voltage, and continue to get the current increase advantage.

Say a panel has a VMP of 30 volts. On the PWM controller, it still gets jumped right to the battery and it stalls out at just 2 amps into the 12 volt battery. Call it 13.5 volts as it is still charging. This is putting 27 watts into charging the battery. Put this same panel through an MPPT controller, and it "finds" the maximum power up at 30 volts, at a slightly less 1.85 amps. It uses the buck converter to translate the 30 volts down to 13.5 volts at the battery. In this extreme case, the MPPT could put about 4 amps into the battery, or 54 watts. Double the charging power from the same panel. In most cases, it won't be that much difference, but I wanted to prove a point. If the panel VMP is close to the battery, PWM is just fine, but the more the VMP is above the battery, the better an MPPT controller will do. But at full current or close to full charge, both have to limit power to protect the battery.

Smart controllers can separately monitor the charge power and load and increase current from the solar to supply the load as long as the charge current is not over the set maximum. This can be very helpful on smaller systems. If it always limits to just the charge current, if you are pulling 10 amps to an external load, that is 10 amps less charge current going to the battery. And if it is limiting power to reach the charge current, there could be solar power that could help run the load and get back to higher charge current.

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There are two different methods used by the controller to regulate the power from the solar panel to charge the battery.

• MPPT (Maximum Power Point Tracking)
• PWM (Pulse Width Modulation)

MPPT charge controllers means that they can continuously track the maximum power point of the solar panel array to ensure maximum power output under varying conditions like shading, temperature changes, and panel degradation. The PWM controller regulates the charging current by rapidly switching the connection between the solar panel and the battery bank, maintaining the battery voltage at a constant level.

PWM charge controllers are an older technology and are cheaper, but less efficient than MPPT charge controllers. Both are widely used and perform similar functions of preserving the life of your batteries. 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. Also, we highly recommend purchasing a high quality charge controller since controllers only account for a small portion of the total system cost. Both pulse width modulation and maximum power point tracking charge controllers have a lifespan of about 15 years, although that will vary based on the specific controller.

What is PWM Charge Controllers

The pulse width modulation controller was the original charge controller used and are simpler and less expensive than MPPT controllers. PWM controllers regulate the flow of energy to the battery by reducing the current gradually, called "pulse width modulation". When batteries are full, PWM charge controllers continue to supply a tiny amount of power to keep batteries full. PWM controllers are best for small scale applications because the solar panel system and batteries have to have matching voltages. This becomes a much more difficult with larger installations.

Cost: $20-$60

Pros of PWM charge Controllers

• Cheaper than MPPT controllers

• Best for smaller systems where the efficiency is not as critical

• Typically longer lifespan due to less components that may break

• Best for warm sunny weather

• Performs best when the battery is near the full state of charge

Cons of of PWM charge Controllers

• Less Efficient than MPPT controllers

• Because solar panels and batteries have to have matching voltages with these controllers, they are not ideal for larger, complex systems

Best for: Those with smaller systems (vans, RVs, tiny homes), those living in warmer climates

What is MPPT Charge Controllers

Maximum Power Point Tracking controllers are efficient at using the full power of your solar panels to charge your batteries. They limit their output to ensure batteries don&#;t get overcharged. MPPT controllers will monitor and adjust their input to regulate your solar system&#;s current. MPPT controllers step down the voltage and boost the current. The overall output will increase as a result and you can expect efficiency ratings of 90% or higher. MPPT charge controllers are more common nowadays

For example, if it becomes cloudy, your MPPT charge controller will decrease the amount of current drawn in order to maintain a desirable voltage at the output of the panel. When it becomes sunny again, the MPPT controller will allow more current from the solar panel once again.

Cost: $100-$729

Pros of MPPT charge Controllers

• Highly efficient

• Best for larger systems where the additional energy production is valuable

• Ideal for situations where the solar array voltage is higher than the battery voltage

• Best in colder, cloudier environments

• Performs best when the battery is in a low state of charge

Cons of MPPT charge Controllers

• More expensive than MPPT controllers

• Typically shorter lifespan due to more components

Best for: Those with larger systems (cabins, homes, cottages), those living in colder climates

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What is the Difference between MPPT and PWM Charge Controller

Here are some main key differences between MPPT and PWM Solar Charge Controller:

Efficiency

MPPT controllers are more efficient than PWM controllers, particularly in varying weather conditions. They ensure that the solar panels operate at their maximum power point, which translates into more energy being harvested and stored.

Complexity and Cost

PWM controllers are simpler and less costly, making them suitable for small-scale and budget-conscious applications. MPPT controllers, on the other hand, justify their higher cost with improved performance and energy efficiency, ideal for larger or more demanding systems.

Performance in Different Conditions

MPPT controllers outperform PWM controllers in cold temperatures and low-light conditions. They are adept at adjusting to fluctuating environmental conditions, whereas PWM controllers tend to be less flexible.

Application Suitability

PWM controllers are often sufficient for small, simple solar setups, such as basic residential systems or small off-grid applications. MPPT controllers, due to their higher efficiency and versatility, are better suited for larger systems, including commercial installations and complex off-grid systems.

How to size your charge controller (mppt vs pwm)

Overall, charge controller sizing is not as difficult as you may think. 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.

Typically, charge controllers come in 12, 24 and 48 volts. Amperage ratings can be between one and 60 amps and voltage ratings from six to 60 volts.

If your solar system's volts were 12 and your amps were 14, you would need a solar charge controller that had 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 our solar charger controller must have to 17.5 amps. We&#;ll round up in this case, so in the end, you would need a 12 volt, 20 amp solar charge controller.

When it comes to charge controller sizing, you also have to 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.

What to consider with MPPT charge controllers: Because MPPT controllers limit their output, you can make 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. MPPT controllers will have an amp reading for it, for example a 40 Amp MPPT Controller. Even if your panels have the potential to produce 80A of current, an MPPT charge controller will only produce 40A of current, no matter what.

What to consider with PWM charge controllers: 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.

What is the upper voltage limit?

All solar charge controllers have an upper voltage limit. This refers to the maximum amount of voltage the controllers can safely handle. Make sure you know what the upper voltage limit of your controllers is. Otherwise you may end up burning out your solar charge controller or creating other safety risks.

How to Choose the Right Solar Charge Controller

The following factors should be considered when buying a charge controller:

• Your budget

• Lifespan of the technology

• Climate where your system will be installed

• How many solar panels you have and how high your energy needs are

• Size, number, and type of batteries you&#;re using in your system

Common Charge Controller Mistakes and Errors

Because of all the different components of a solar installation, it can be easy to make a misstep in the installation process. Here are a few commonly made mistakes when it comes to solar charge controllers.

• Do not connect AC loads to the charge controller. Only DC loads should be connected to the charge controller&#;s output.

• Certain low-voltage appliances must be connected directly to the battery.

• The charge controller should always be mounted close to the battery since precise measurement of the battery voltage is an important part of the functions of a solar charge controller.

Conclusion

Both MPPT and PWM solar charge controllers have their advantages and considerations. MPPT controllers offer higher efficiency, faster charging times, and increased energy harvest, making them suitable for larger solar systems. PWM controllers provide a cost-effective and reliable solution for smaller systems. By understanding the differences and evaluating your system requirements, you can make an informed choice.

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