MPPT and PWM Main Differences in Solar Charge Controller

Admin@AKR Technical

MPPT and PWM Solar Charge Controller differences, advantage and disadvantages are discussed in detail in this article.

What is MPPT Controller?

Charge Controller an MPPT (Maximum Power Point Tracking) is a controller used to optimize the connection between solar panels and your battery, utility and grid supply. The maximum power point (MPP) is the optimal point on the I x V curve between current and voltage. These are fed into the system at the maximum current that can be generated in a given moment from the PV panel.

MPPT and PWM Main Differences in Solar Charge Controller

Difference between MPPT and PWM charge controller

PWM (pulse width modulation) and MPPT (maximum power point tracking) charge controllers are DC to DC converters that convert the voltage output voltage from the solar panels to a voltage more suitable for charging the battery bank. PWM charge controllers are usually older and cheaper devices. These are for small systems only. They have a charging efficiency of only 70% to 75% of the current generated by the solar panel.


The main difference between MPPT and PWM charge controllers is that the MPPT charge controllers allow the PV array output voltage to be higher than the battery bank. It also converts the high voltage received from the PV array output into high current and charges the battery. This means that the battery is fully charged and the grid supply is cut off to operate other electrical equipment and the output of the PV array output voltage is changed directly.


A standard PWM charge controller can only control the output voltage of the PV array. But it cannot convert the over-produced PV array voltage into current. A PWM charge controller can only maintain the same current as the PV array. This means that there are no systems in place to make full use of the output power (current x voltage).


MPPT Controller

MPPT controllers are second generation solar controllers. Compared to the PWM controller, it incorporates more control devices such as power Transistors, Inductors and power Diodes. So, it shows more powerful actions.


As an MPPT charge controller monitors the PV array for maximum power point, it will track the output voltage of the PV array and try to increase the maximum current. Normally, this increases the voltage coming from the PV array to the current and maintains the majority of the total output power.


The use of MPPT is essential for large PV systems, as it greatly improves system design and performance. MPPTs are made in multiples of the 12V range, which is a typical battery voltage. It is usually used in series (12V, 24V, 36V, 48V, 60V, 72V) up to 72V. So far it has been said about the off grid solar system because the batteries used for backup are off grid. There is no need to use batteries for backup on-grid as it works by grid supply sense.


Advantages of MPPT

MPPT charge controllers are modern technology, because they are done with, these will work more efficiently. This means that its DC to DC efficiency is 90% to 97%. Many companies seem to offer more flexibility when it comes to design. MPPTs can be built from small systems to large systems. Another advantage is that they get longer warranties from the manufacturer.


Disadvantages of MPPT

  • The MPPT charge controller is more expensive than the PWM
  • The size will be larger

PWM vs MPPT difference in design flexibility;

Scenario 1: PWM

If a PV system is designed with a PWM charge controller. We choose to use a 250 watts solar panel with 26.31volt Vmp and 9.5 amps Imp.

Calculation: Vmp x Imp = maximum power point

26.31V x 9.5A = 250Wats

9.5A (Imp module of PV module x 12V (battery voltage) = 114W

If a 12V battery is used as the storage system. Ignoring the charging features of the battery, the output voltage of the solar module can be reduced to 12V to charge the battery. But if a PWM charge controller is connected, it can be assumed that the output current is uncontrollable and the following result will be obtained.


9.5A (Imp module of PV module x 12V (battery voltage) = 114W

 The loss here is 250 - 114 = 136 watts.

 114W is much less than the panel's maximum power output of 250W.

Scenario 2: MPPT

Design a PV system with an MPPT charge controller. It can be calculated using the same solar module mentioned above. The PV output voltage has to be reduced to match the charging voltage of the battery by about 12V. However, the MPPT output current is increased at this time to maximize the overall power transfer.


Follow these calculations to find out what the optimal current rating of the output would be.


Maximum Panel Output Power / Battery Charging Voltage * Temperature Correction Factor

 250W / 12V x 1.25 = 26.04A

This means that the maximum output current can be obtained from the MPPT, causing very small losses.  

Selection of MPPT and solar panels

Solar panels are available in 12 volt and 24 volts. E.g. 100 watts - 12 volts, 275 watts - 24 volts, 380 watts - 24 volts, 395 watts - 24 volts, 440 watts - 24 volts. Poly crystalline and Mono PERC crystalline solar panels are available in the market today in many sizes, watts and volts. So, choose only after you have a good understanding of solar panels. These are selected based on various factors, mainly space constraints. Learn more about Solar Panels.



PWM and MPPT controllers have their own advantages and disadvantages. Depending on the design features, cost, external control and environment of the solar photovoltaic array, decide which scheme to choose.


If the output current of the larger panels mentioned above cannot be adjusted, there may be a significant voltage difference causing power loss. Only one MPPT can convert it to current as it receives more voltage from the output of larger panels. It is in this context that the differences and significance of MPPT and PWM need to be understood.

Post a Comment


Please Select Embedded Mode To show the Comment System.*