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What Is A PWM Controller

What Is A PWM Controller

Do you intend to understand what the PWM controller is? This article has every information you require to quench your curiosity.

In this modern time, a charge controller helps you run your batteries more efficiently by reducing the amount of electricity flowing into them. In addition, it aids in the safe and long-term maintenance of your battery.

For the sake of clarity, I will start with an overview of the PWM controller. Then, I will give details on how it works.

Subsequently, the following sections will contain the difference and specifications of PWM and MTTP charge controllers. After which, I will discuss the basic operation and sizing of the PWM controller.

Furthermore, I will discuss the 3 stages of charging a PWM controller, applications of the PWM controller, factors to consider before buying a PWM controller, and the rating of charge controllers respectively.

Then, I will list the pros and cons of PWM controllers. After which, I will give my recommendations for the 5 best PWM controllers.

In conclusion, I will give answers to some frequently asked questions on solar charge controllers.

I strongly suggest you read through the reviews of these PWM solar controllers in this article to get a pretty idea of which one is good.

What Is A PWM Controller: Overview

What does PWM charge controller mean_

First thing first, the word PWM stands for pulse width modulation.

A PWM is an effective control measure that allows you to control the speed of motors, heat output, etc., in an energy-efficient manner.

A PWM controller is a switch between the solar panels and the battery. You can easily switch it on or off.

A current regulator prevents batteries from overcharging or over-discharging when charging by gradually reducing the current.

For clarity, a PWM controller is a device that uses very fast switching many times in a second. For this reason, it controls the current flow from a PV panel to a battery for charging.

As in a standard battery charger, PWM can quickly adapt to different types of batteries for your charging.

What Is A PWM Controller: How It Works

What Is A PWM Controller - How It Works

Generally, a solar panel’s voltage is higher than the battery’s voltage. As such, it is good when the battery needs a lot of recharging, but not so nice if it is closer to full charge.

The PWM controller monitors your battery voltage and decides the amount of current it can safely feed into.

Furthermore, the circuit then uses up the voltage into pulses of the same voltage. For instance, if the pulses are long, the average voltage and the charge current are higher.

Likewise, if the pulses are shorter, the voltage and the charge current will be low.

For more clarity, the pulses are always longer at the beginning of the charging cycle when more current is required for fast charging. It also becomes shorter towards the end of the charge.

Using a PWM charge controller, a 12-volt solar panel is required to charge a 12-volt battery.

Therefore, a PWM charge controller with a 12V battery on a 48V solar panel will not collect extra energy. Instead, it collects only 12V.

Conclusively, PWM connects your solar array directly to the battery bank. So as your battery chargers, the battery voltage rises, which increases the solar panel voltage that is charging the battery.

Difference Between PWM And MPPT Solar Charge Controllers

The significant difference between pulse width modulation (PWM) and maximum power point tracking (MPPT) are:

The PWM controller absorbs current from outside the panel above the battery voltage.

The current is absorbed outside the panel using an MPPT controller at the solar panel’s maximum power voltage.

As panel voltage rises, an MPPT controller will return higher than a PWM controller.

Using MPPT controllers gives you an increase in energy collecting. However, the percentage increase changes during the day.

Panel voltage and battery have to be the same in PWM systems. Whereas in the MPPT system, the series panel is allowed to have a higher voltage than batteries.

Specification Of PWM And MPPT Charge Controller

Battery Voltage

The PWM charge controller operates at the battery voltage, whereas the MPPT controller uses the above battery voltage to provide a boost to a low battery.

Array Voltage

A PWM controller battery voltage and PV array voltage must be the same. On the other hand, the MPPT controller PV array voltage can be higher than the battery voltage.

System Size

The PWM solar charge controller has a smaller system operation, while the MPPT solar charge controller works best for 150-wattages or higher systems.

If you are still confused, pick a PWM charge controller if you need it for Small systems- for example, your RV with AGM deep cycle batteries.

This is especially true when efficiency, like trickle charging your boat battery, is not essential. A solar panel with a PWM of around 18V would suit well to charge a 12V battery.

PWM charge controllers are cheaper and less expensive when you don’t want to spend much money.

Basic Operation Of A PWM Controller

Basic Operation Of A PWM Controller

For a PWM controller to be seen as a switch between the solar panel and the battery;

The device switch is turned ON once the charging mode is in multiple charges.

The device is shut off at the absorption end as the voltage level drops to the floating voltage.

As usual, the switch is “swiped” on and off to keep the battery voltage at the absorbing level (PWM).

Similarly, this switch “turns” on and off as needed to retain the float voltage in the cell.

For clarity, when you turn off the switch, the voltage on the panel will be at an open-circuit voltage (Voc).

Also, the voltage on the panel will be at battery voltage, and the voltage drops between the panel and the controller once the switch is on.

Sizing Of A Pulse Width Modulation Charge Controller

It’s critical to ensure your charge controller is compatible with your panels and is the right size.

When looking for a charge controller, there are some factors to consider when looking at the list of specs.

PWM controllers, for example, should contain amps readings, such as a 30 amp PWM controller.

Specifically, the amperage and voltage rating are the two items you must check in a PWM controller.

To begin, check the system’s nominal voltage. By looking at this, you’ll be able to tell what voltage battery banks the controller is compatible with.

Check the battery’s rated current. You have a charge controller with a 30 amp rating, for example.

Then, compare the 30 amps to a safety factor of 1.25 times 1.25 of the current from the panels.

Take a look at the highest solar input. This will tell you the highest volts limit that can be fed into the controller.

It won’t take anything more than 50 volts. Also, it would be best if you verified the terminals.

The terminals on every controller should have a maximum gauge size. Finally, it would help if you examined the battery.

This will allow you to determine the correct battery for your controller.

Pulse Width Modulation 3 Stage Charging

Bulk Charge

Bulk charging is when your solar panel device speeds up the battery’s charge. At this level, when the voltage is low, the gadget will recharge your battery with high voltages and currents.

Direct charging must be stopped if the voltage at the battery’s end is more vital than this maintenance value while setting.

Absorb Charge

After the first charging stage, the battery will wait for some time to allow the voltage to drop as usual. After that, it will reach the normal charging level, and this stage is referred to as constant voltage charging.

Float Charge

The last stage of charging is also known as trickle charging. The tickling is a low-level and consistent charging current for your battery.

Due to self-discharging, most rechargeable batteries lose their energy when charged. It can retain charging capacity if the charge remains at the same low current due to self-discharge.

Applications Of PWM Controller

Here are a few examples where we can apply solar charge controllers: Use a Solar panel module or PV for household purposes in your home systems.

Hybrid solar panels use different energy sources to promote overall backup supplies to other sources. Street lights use solar panels to convert sunlight to DC charge.

For this reason, the solar panel uses a solar charge device to store DC in your batteries for several locations.

Factors To Consider Before Buying A PWM Controller

Factors To Consider Before Buying A PWM Controller

When purchasing PWM solar charge controller, keep the following factors in mind:

  • You must consider your budget when purchasing a solar charger. This will allow you to select the most appropriate one for your best option.
  • Again, it would be best to look at the solar charge’s longevity. You’ll be able to tell whether it’ll last longer and be handier.
  • The weather conditions of the location where you intend to put it are essential to consider. In cold weather, most charge controllers perform admirably.
  • You must also evaluate the number of solar panels you select and the amount of electricity you need.
  • Measure the size and kind of batteries you’ll need for your solar system.

How To Connect A Solar Charge Controller To A Battery

Most batteries have a terminal voltage of 12 volts for auto and marine operations. The two major types of batteries commonly used are lead-acid in different forms and lithium-based.

More precisely, a variety of batteries requires various charging functions. Although, all this type of batteries has the same primary connections.

Simply put, the solar panels connect to your controller’s positive and negative terminals. After that, the output will connect to your battery terminals.

From the battery terminal, you may connect or may not connect your loads in parallel with the battery.

The basic block diagram of PWM is illustrated above to give you more ideas on how to connect a charge controller.

Ratings for Different Solar Charge Controller

Many brands of solar charge controllers come with a wide range of input voltages, output current, and voltage.

Different models of charge controllers can adapt to battery voltage from 12V to 24V, but the expensive type has a higher range limit of 72 volts.

It is indispensable for large battery banks and helpful for people who stay off-grid. Meanwhile, solar panel input voltage changes from 24 volts to 250 volts.

In addition, if you are to install a smaller system on a budget. Eventually, you will buy a cheaper solar charge controller with the highest input voltage of 24V.

It is suitable for connecting two, three, or more parallel forms. The voltage will remain the same while the current rises.

It makes sense when you connect solar panels in series form in some situations. The output voltage will be around 42. For example, you have to double the panel with only one.

Tips for PWM Solar Charge Controller

  • Make sure you connect the batteries before the solar panels- it gives you reference voltage.
  • Always store the solar charge controller in a well and ventilated place.
  • Purchase the best design that your money can afford – less expensive can fry your batteries.
  • Always go for a solar charge controller with 50% more capacity than your need – it is best for expansion.
  • You have to ensure it is a smart type of charge controller to enable you to monitor the panel and battery voltage.

What Is A PWM Controller: Pros and Cons


  • It is perfect for a smaller system where the efficiency is not bad.
  • The PWM solar charge controller has a longer lifespan due to a few components that may break.
  • It performs better when the battery is almost in a full state of charge.
  • The cost of production is low and has 99 percent efficiency
  • A signal may be separated easily, and interference can be easily disconnected when receiving audio.
  • Large capacity storage and can also make use of a high frequency.
  • It is extremely energy efficient when it is used to transfer voltage or power to its energy light.
  • This charge controller is durable, also with a passive cooling heat sink style.
  • Unlike pulse position modulation (PPM), there is no need for synchronization between the transmitter and receiver.


  • Less efficient compared to MPPT controller
  • They are unsuitable for more extensive and complex systems since the solar panels and battery must match the voltage.
  • Most smaller PWM charge controller units do not match in terms of conduit wiring.
  • Additionally, this type of charge controller has limited capacity for system improvement.
  • For you to use PWM in communication, the frequency should be high. But again, due to an increase in PWM frequency, there is a large switching loss.
  • A semiconductor device with slow turn-on and turn-off times is required for this system. For this reason, they are quite costly.

What Is A PWM Controller: My Recommendations

What Is A PWM Controller - My Recommendations

This table contains the 5 best PWM charge controllers available. However, I’m listing the top picks in ascending order from the best to the 5th.

ProductDimensionsWeightCurrent RatingBrand
Renogy 10 Amp 12V/24V PWM Negative Ground Solar Charge Controller4.7 x 3 x 1.1 inches0.27 Pounds10 ampsRenogy
EEEkit 30A Solar Charge Controller7 x 13.5 x 2.5 inches0.35 Pounds30 ampsEEEKit
[Upgraded] 30A Solar Charge Controller5.39 x 3.23 x 1.65 inches0.31 Pounds30 ampsDepvko
SUYNIMA 15A Solar Charge Controller5.51 x 3.07 x 1.54 inches0.51 Pounds15 ampsSUNYIMA
PWM 50A Solar Charge Controller7.6 x 3.9 x 2 inches0.95 Pounds50 ampsPowMr

Frequently Asked Questions

Frequently Asked Questions
1. How Does A PWM Charge Controller Works?

The PWM charge controller works by slowly reducing the power going into the battery as it approaches its capacity.
At its full capacity, PWM charge controllers constantly supply a tiny amount of power. This keeps the battery topped off.

2. What Is Better PWM Or MPPT?

The Maximum PowerPoint Tracker (MPPT) is more efficient.

3. Are PWM Controllers Good?

It is a low-cost solution for only small systems when the solar cell temperature is moderate to high.

4. What Happens To Solar Power When Batteries Are Full?

When the battery is full, the battery will stop absorbing power from the solar system.

5. Where Would You Use A PWM Controller?

Pulse Width Modulation (PWM) controllers are most suitable for small-scale applications.

6. What Size Charge Controller Do I Need For A 100W Solar Panel?

The size of the charge controller that suits a 100-watt solar panel is a 10 amps charge controller.

7. What Are The Two Types Of Solar Charge Controllers?

Maximum Power Point Tracker (MTTP)
Pulse Width Modulation (PWM)

8. What Does A Charge Controller Do?

It regulates the amperage and voltage that goes into the load.

9. What Is An MPPT Inverter?

It is a DC-to-DC converter that optimizes the match between the solar panels and the battery or utility grid.

10. What Does PWM Stand For?

Pulse Width Modulation.

What is a PWM Controller: My Final Thoughts

What is a PWM Controller - My Final Thoughts

Since the primary aim of the PWM charge controller is to charge your battery, it also regulates your battery voltage to make sure it does not get too high to damage your battery.

Meanwhile, a charge controller will take the solar panel’s rising and falling input current. After that, it stabilizes it to ensure your battery is safely charged.

Ultimately, a charge controller will protect your device from the risk of fire blowing out and charge your batteries faster and more effectively.

I hope you found this PowerVersity pick helpful.

If you found it helpful, kindly share your thoughts with the “Leave a Reply” form found towards the end of this page.

Finally, to read more guides like this, visit our Inverters & Charge Controllers page.

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