Solar energy is one of the most viable sustainable energy sources for a world grappling with going green. Many residential, commercial, and industrial buildings have huge solar panels installed to supplement energy needs.
Solar panels charge batteries that supply power, but the current amperage needs to be regulated to avoid overcharging, overheating, and possible explosion.
That is where the solar charge controller comes in. There are two types of solar power controllers: PWM and MPPT. So, MPPT Vs. PWM, which one is better?
Maximum power point tracking (MPPT) is more efficient than Pulse width modulation (PWM) in terms of maximizing charging capacity as MPPT charge control devices have 30 % more efficiency in charge efficiency. PWM charge controllers are generally better for smaller solar arrays between 300 to 400 watts or less. In contrast, MPPT charge controllers are typically better for larger solar arrays of 400 watts.
The controller modulates the voltage from the solar panels to the batteries. The system’s efficiency also reduces heat and the amount of power discharged from the batteries to meet your household’s requirements.
Let’s discuss MPPT Vs. PWM, how do these solar controllers function, and which is ideal for your needs?
Are you interested in exploring the pros and cons of Solar Energy? I wrote an article where I discussed the benefits and drawbacks of adopting solar energy; I encourage you to check the article out.
What Is a Solar Charge Controller, And What Does It do?
A solar charge controller (often called a regulator) is comparable to a regular battery charger, regulating the current flowing from the solar panels into the battery bank to prevent overcharging the batteries.
The primary role of the charge controller is to regulate the voltage and current flow from the PV panels to a battery. A Solar charge controller generally detects and monitors the battery voltage and reduces the current once the battery is fully charged.
There are generally two different kinds of charge controllers on the market:
- Pulse Width Modulation (PWM)
- Maximum Power Point Tracking (MPPT)
What Is a PWM Solar Controller?
PWM is an abbreviation for Pulse Width Modulation. It acts as an electronic switch between batteries that can quickly switch on and off to attain the desired voltage. As the batteries charge, PWM gradually decreases the current that enters them to prevent overcharging.
It was challenging to charge batteries with the solar system in the past. Old systems came with simple on-off regulators to reduce the chances of batteries outgassing in case of excess energy from the panels.
However, these simple controllers interfered with the charging process. They also contributed to early battery failures and load disconnect, contributing to user dissatisfaction.
PWM came to the rescue with advanced technology. This controller reduces the charging current when the voltage reaches the regulation setpoint to avoid gassing the battery.
The regulated current slowly charges the battery until it has attained maximum energy. PWM provides higher charging efficiency, healthy battery life at full capacity, and rapid recharging.
PWM has a three-stage charging: bulk charge, absorb charge, and float charge. Let’s briefly explain what they mean.
Bulk Charge: Bulk charging happens when the PV device does much of the charging, especially when the battery voltage is down. The device channels high voltage and current into the battery. Bulk charging should stop when the battery voltage has risen above the maintenance value level.
Absorb charge: After the bulk charging, the battery will transcend to a period of constant voltage charging, where the voltage from the panels naturally decreases to a balanced charging stage.
Float charge: This is the final stage in battery charging, called Trickle charging. At this stage, the battery needs a slight charging current at a steady and low rate. This low current charge increases the battery’s charge capacity.
Advantages of PWM
- It is relatively cheaper than MPPT solar charge controller
- Longer lifespan since it has less thermal stress and fewer electronic components
- It is smaller in size, hence easy to deploy and handle
- It has a smaller system with less difference between battery voltage and solar panel output.
- Reduced battery gassing and heating
- It is self-regulated to accommodate battery drops and to change temperatures from the solar systems.
Drawbacks of PWM
- It is not as efficient as MPPT solar controller
- It generates less voltage, thus supporting low capacity.
- It is not ideal for larger systems, especially when the solar panel output exceeds the battery voltage.
- It does not have load and voltage difference optimization
What is An MPPT Solar Charge Controller?
This abbreviation stands for Maximum Power Point Tracking. It has a unique technique to regulate the amount of energy from the solar panels entering the batteries.
Depending on the weather conditions, the solar panel will show you the changeable output, and the MPPT control device will match the voltage from the solar panels to the battery capacity for improved charge efficiency.
You can charge your batteries with full-power solar panels since MPPT balances the voltage and the current using the equation P= V X A. For instance, during cloudy weather, the controller reduces the amount of current the PV modules draws from the solar panels to protect the voltage.
And during sunny weather, the controller allows the PV device to draw more current. Increasing amperage contributes to faster recharge since the controller automatically adjusts according to the equation P= V X A. This means you will have more power to charge the battery with no loss.
MPPT is an ideal DC to DC converter that fully utilizes the solar panels’ power output. Since sunlight’s charging degree often changes during the day, the panels’ current and voltage often vary.
This solar charge controller is programmed to monitor and change solar panels’ voltage, thus enhancing electricity production regardless of weather conditions.
Advantages of MPPT Solar Charge Controller
- It can work with solar panels with a higher voltage than the battery bank, which is beneficial in areas with low sunlight or during winter.
- It contributes to increased charging efficiency- 30% better than PWM.
- They have a higher warranty period.
- It is ideal for system growth, especially for commercial establishments
Disadvantages of MPPT
- It is costlier than PWM solar charge controller
- It has more electronic components, thus contributing to more thermal stress and a shorter lifespan.
- It is challenging to handle due to its enormous size.
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What Are The Difference Between PWM and MTTP?
The major differences between PWM and MPPT charge controllers are conversion efficiency and cost. MPPT charge controllers are more efficient, but they are relatively more expensive. In contrast, PWM charge controllers are typically cheap and less efficient.
The solar power system needs the charge controller to function properly, but to determine which system is better, you need to do some analysis.
Let’s consider the PWM and MTTP to establish which one is better.
If you are using maximum charging capacity as a factor in choosing a solar charge controller, MTTP will carry the day. Nevertheless, these two technologies vary greatly, each having its strengths and weaknesses.
Your decision will largely depend on system components, site conditions, size of load and array, and cost.
1- Temperature Conditions
MPPT controller works well during colder conditions. As the temperature drops, the Vmp1 increases. Why? The solar panels’ operating voltage at their maximum power point is approximately 17V at standard testing conditions of 25C° when the battery voltage is roughly 13V.
MTTP taps into the excess module voltage during low temperatures and charges the batteries.
On the other hand, PWM solar charge controller struggles to capture the excess voltage since its technology supplies the same voltage as the battery. But when used in hot or warmer climates, their peak power point decreases to a voltage closer to the batteries. PWM does not transfer excess voltage to the battery.
2- Array To Load Ratio
If the solar array is greater than the power from the batteries, the batteries will remain close to a fully charged state.
In this case, you can use the PWM controller to maintain an efficient system without needing an MPPT controller.
3- Size Of The System
PWM works best with low-power systems than MTTP because:
- They have a relatively constant harvesting capacity regardless of the array from the panels.
- They are less costly than MTTP, making them ideal for smaller systems.
- MTTP controller needs high-power applications (170W and above), which means they would be less efficient with low-power systems.
4- Cost
PWMs are less expensive than MTTPs; however, under certain conditions, MTTPs produce more power than PWMs using the same solar modules.
You could analyze the site to establish if MPPT can perform efficiently to compensate for the cost before installation.
It is also important to evaluate the system’s total cost before using price as a determining factor.
Comparison Summary
The table below summarizes the differences between PWM and MTTP.
| MTTP Charge Controller | PWM Charge Controller | |
| Array Voltage | It can be higher than the battery voltage. | The battery voltage and the PV array voltage should match. |
| System size | The system should be 150W- 200W or higher. | Works well with smaller systems that MTTP cannot work with. |
| Battery voltage | It works above battery voltage, hence suitable in cold temperatures | Work at battery voltage and performs better during warm or hot temperatures. |
| Array sizing method | PV array sizing measured in Watts | PV array sizing measured in Amps |
| Off-Grid or Grid-Tie | It allows the use of grid-tie PV modules, thus reducing overall system cost. | It only uses off-grid PV modules. |
MPPT Vs. PWM: Which One Is Better?
Many reviews show that MTTP is 30% more efficient than PWM. But what makes MTTP superior? Consider some factors. When the solar panels have a high-power output, it also generates characteristic resistance (the panel’s internal resistance). MPPT controller capitalizes on this solar panel resistance by matching it with its own internal resistance to draw maximum power.
On the other hand, the PWM controller is less efficient because it lowers the solar panel voltage to match the battery voltage. This means that a lot of sunlight energy hitting the panels is wasted.
- Choose a PWM solar charge controller if:
- You have a for smaller systems (300-400W or less)
- The efficiency of your system is not essential, for instance, trickle charging.
- Your solar panels have a maximum power voltage (Vmp) of up to 18V and charge a 12V battery (36V for a 24V battery).
- And choose an MPPT controller if:
- If you have a larger system (more 400W) and want to increase its efficiency by about 30% more.
- Your solar array voltage is significantly higher than the battery voltage. Let’s say you are using house panels to charge 12V batteries.
Are MPPT controllers worth it? MPPT controllers are worth it as the peace of mind and the extra efficiency you gain are worth the additional price you pay. Even though a PWM controller is relatively cheaper than an MPPT, investing in an MPPT controller will provide higher benefits in the long term.
Conclusion
MTTP solar charge controllers are suitable for individuals looking for a controller that can handle demanding tasks. It can be cost-effective by reducing other expenses while supplying much power.
PWM solar charge controller works well with small off-grid power applications. They are effective for households looking for a basic charge controller. If you want power for your lighting system, you can install PWM to save on investment costs.