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?
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?
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.
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 and Cons of PWM Solar Charge Controller
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?
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?
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.
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.
Last update on 2021-09-05 at 22:45 / Affiliate links / Images from Amazon Product Advertising API