MPPT vs PWM : Which Solar Charge Controller Should You Choose?

Solar Gear Expert is supported by readers. If you buy through links on our site, we may earn an affiliate commission at no extra cost to you.

MPPT vs PWM Charge Controller

A solar charge controller is essential for any solar power system that uses batteries. It is primarily responsible for regulating the power that flows from the panel to the battery to prevent overcharging. This ensures that batteries only charge to their required capacity (maximum).

There are three types of charge controllers; simple 1 or 2 stage controls, pulse width modulation, and maximum power point tracking. However, in this guide, we will focus on MPPT and PMW as they are the major types of solar charge controllers. This is in a bid to finally settle this MPPT vs PWM charge controller debate that has been making rounds for long now.

What is MPPT Solar Charge Controller?

Victron SmartSolar MPPT 100/20

The maximum power point tracker is a solar charge controller technology used to optimize and control power voltage from the panel to the battery. It converts an electronic DC-DC maximizing the match between PV panels and the battery grid.

With the MPPT solar charge controller, the current is matched to equate the panels current and the battery’s voltage. It has a smart element that adjusts input voltage, matching it with that of the battery.

So how does MPPT charge controller work?

Primarily, MPPT charge controllers ensure that the voltage is lowered to provide the battery with charge. PWM controllers work by regulating the charge rates of the battery from the voltage of the solar panels. They hold the solar panel voltage more constant.

If it has two-stage verification, it will first keep the energy to a safe maximum for the battery to get fully charged. The controller then drops the solar panel’s voltage to sustain a safe battery charge without damaging the voltage control.

However, it depends on the type of battery and solar panels used in the solar power system.

What is PWM Solar Charge Controller?

Renogy Wanderer

It refers to an electronic DC to DC converter that regulates the voltage output from solar panels by reducing the voltage to a lower level suitable for battery charging. It is one of the traditional technologies used in solar charge controllers.

For the PWM when absorption is complete, the switch goes off with the battery voltage dropping to float voltage. You can flick the switch to either mode (ON or OFF), holding the battery’s voltage.

MPPT vs PWM Charge Controller : Detailed Comparison

All solar charge controllers are characterized by their ability to protect a battery from overcharging, increasing its lifetime, very high reliability, preventing reverse current flow, and indicating auto charging.

Let’s look at what the distinguishing features are between the two as well as the similarities. This should help you make an informed decision on the best solar charge controller for you.

Solar Charge Controller Comparison

The main difference between MPPT and PWM is in performance. When using the maximum power point tracker (MPPT) controller, the current is drawn out of the panel producing maximum power voltage. It is considered the best (smart DC-DC converter) solar controller in the modern solar power system. It recognizes the most suitable working voltage and amperage of a solar panel output and matches that with the battery. It draws current from the solar panel, slightly higher than the battery’s voltage.

Solar Charge Controller Comparison

On the other hand, when using the pulse with modulation (PWM) controller, the current is drawn out of the panel at just above the battery’s voltage. It draws power despite the panel’s temperature subject to the battery’s voltage being lower than that in the panel. It can be considered as an electronic switch that automatically switches to suit the operation.

MPPT vs PWM Solar Controllers: Similarities

Here are the similarities between the MPPT and PWM solar charge controllers:

  • One of the most evident similarities is that the two solar controllers have regulated solar output voltage between the solar array and the battery to extend battery life.
  • Both down-convert solar panel voltage to the same level as the battery.
  • They both monitor reverse current flow and prevent it.
  • They both protect overcharging and over-discharging.

MPPT vs PWM: Differences

Now let’s look at what makes the two different:

  • PWM is primarily effective for smaller solar charge control units and housing systems, while MPPT is suitable for large power output systems.
  • PWM is only limited to sizes of up to 60 amp, whereas MPPT is available in a variety of sizes of up to 80 amp making them more convenient.
  • The PWM has its switch on during the bulk charge mode. The same is not witnessed in MPPT.

PWM vs MPPT Solar Charge Controller : Pros and Cons

Pros and Cons of MPPT Solar Charge Controller

Pros
  • There is a potential of increasing the efficiency in charging by at least 30%.
  • There is a possibility of experiencing a high array under high input voltage over the battery bank.
  • The device comes in multiple sizes, with the largest size being 80 amps.
  • Its warranty has an extended duration compared to the PWM solar charge controllers.
  • The MPPT has a significant chance of flexibility essential for the system’s expansion.
  • MPPT is the only technology that can regulate the grid connect modules vital for battery charging.
  • They are the most preferred option to control giant connect modules for battery charging.
  • Improves battery life by automatically controlling charging and discharging rates.
Cons
  • It is costly.
  • Its units could occupy a vast space as it is larger.
  • Sizing could be problematic, especially if you have little or no expertise.
  • When using the MPPT, photovoltaic modules are inevitable.

Pros and Cons of PWM Solar Charge Controller

Pros
  • The design has several applications that have multiple sizes.
  • This design has a longer lifespan that results from a cooling style enabled by the heat sink.
  • Compared to the MPPT, the PWM charge controller is inexpensive and could be affordable, costing approximately $350.
  • The PWM’s technology has been tested over the years and is bound to be constant with modernization.
Cons
  • There is no way you can operate the device if the nominal voltage does not match with the battery’s voltage.
  • Presently, there has been no provision of a single sized controller that can exceed 60 amps.
  • Most of its units are not listed on the Underwriter Laboratories (UL) certification.
  • A majority of its designs exclude the conduit in its systems.
  • The possibility of system expansion is next to zero.
  • It is not effective where the system’s operation is critical.
  • It is ideal for panels whose maximum power voltage is 18V for charging a 12V battery.
  • The PWM is not effective when subjected to higher voltage grid connect modules.

Sizing Solar Charge Controllers

Sizing both MPPT and PWM solar charge controllers is almost similar based on calculations. The difference is that the MPPT controllers can be used in solar arrays with very high voltage compared to PWM, thus a variation in voltage.

How to Size MPPT Solar Charge Controller?

EPEVER 40A MPPT

Sizing an MPPT solar charge controller is simplified, as highlighted. If you are using more than one solar panel in your system, take the number of the panels and multiply by the watt of one to get the total wattage of the solar array. Then, divide the total number of watts by the voltage of your battery bank to get amps, and then add 25% to give room for the cold temperatures.

If it seems challenging getting the right calculations, then check out this example to understand better.

Let’s take the number of solar panels to be 2 with 140w each and a battery bank with 12v.

Our calculations will be, 2*140 = 280w/12v + 25% = 29.18 amps.

So if you were to select an MPPT controller you would pick one with this or higher than that.

How to Size PWM Solar Charge Controller?

Renogy Adventurer 30A

When sizing the PWM charge controller, choose one that has some nominal voltage through your system. That is the solar panel array, PWM controller, and the battery bank.

For instance, if the solar panel has 12V, the solar charge controller should have 12V and the same applies to the battery bank. That is, 12v=12v=12.

Since temperature keeps changing, you need to size the current due to the solar panel’s current output variation. To calculate the current, you use a standard factor that caters for all photovoltaic (PV) output-boosting circumstances. The factor is usually 1.25 or 125%. You then take the solar panel’s short circuit current often indicated at the back of the panel and multiply it with the factor, that is, solar panel (Isc) 1.25 = minimum charge controller amperage (A) rating. Then select a solar charge controller with a rating equal to higher than the rated value obtained above (A).

When you use a solar system in a continuous operation, it is advisable to use additional protection. A continuous operation system is one that puts into use for more than three hours continuously. It is calculated by multiplying the standard factor with the de-rated value obtained above. Then you select a solar controller that has such amperage or higher than that.

Final Thoughts

When contemplating the best solar charge controllers to purchase, there is a lot you have to figure out as choosing a well-established charge controller is essential to a lifelong and efficient solar power system.

Back to the biggest question – MPPT vs PWM charge controller, which is the best?

The answer is simple really. If you need a cheap and suitable controller for a smaller solar power system, then PWM is your best bet. However, if you need a super-efficient solar controller that can perfectly work in a large solar power system and more durable, MPPT is the best choice.

41Shares

Last update on 2021-09-05 at 22:45 / Affiliate links / Images from Amazon Product Advertising API

Scroll to Top