MPPT vs PWM Charge Controllers
What are solar charge controllers?
The solar charge controller sits between the energy source and storage and prevents overcharging of batteries by limiting the amount and rate of charge to your batteries. percent capacity and charge the batteries at the correct voltage level. This helps preserve the life and health of the batteries. They also offer some other important functions including overload protection, low voltage disconnects, and block reverse currents
Before we get into the technical details of the difference between PWM: Pulse-Width Modulation and MPPT: Maximum Power Point Tracking let’s summarise the article for those who feel are not technical but just want to know which controller is better?
In order to get the maximum out of a solar panel, a charge controller should be able to choose the optimum current-voltage point on the current-voltage curve: the Maximum Power Point. An MPPT controller does exactly that.
The input voltage of a PWM controller is, in principle, equal to the voltage of the battery connected to its output (plus voltage losses in the cabling and controller). The solar panel, therefore, is not used at its Maximum Power Point, in most cases.
To understand the difference between PWM and MPPT charging, let’s first look at a typical power curve of a PV panel. The power curve is important because it states the expected power generation of the panel based on the combination voltage (“V”) and current (“I”) generated by the panel. The optimal ratio of current to voltage to produce the most power is known as the “Maximum Power Point” (MPPT). The MPPT will change dynamically throughout the day depending on irradiation conditions.
Pulse-Width Modulation (PWM) comes into play when the battery bank is full. During charging, the controller allows as much current as the PV panel/array can generate in order to reach the target voltage for the charge stage the controller is in. Once the battery approaches this target voltage, the charge controller quickly
switches between connecting the battery bank to the panel array and disconnecting the battery bank, which regulates the battery voltage holding it constant. This quick switching is called PWM and it ensures your battery bank is efficiently charged while protecting it from being overcharged by the PV panel/array.
Maximum Power Point Tracking features an indirect connection between the PV array and the battery bank. The indirect connection includes a DC/DC voltage converter that can take excess PV voltage and convert it into extra current at a lower voltage without losing power.
then adjusts the incoming voltage to maintain the most efficient amount of power for the system.
The table below summarises the pros and cons for each of the two controllers. Last we also give our advice on which controller to get
|Pros||Cheaper than MPPT controllers |
Best for smaller systems where the efficiency is not as critical
Performs best when the battery is near the full state of charge
Performs better in sunny weather
Best for larger systems where the additional energy production is valuable
Ideal for situations where the solar array voltage is higher than the battery voltage
Performs better in winter weather
Performs best when the battery is in a low state of charge
|Cons||Less Efficient than MPPT controllers Because solar panels and batteries have to have matching voltages with these controllers, they are not ideal for larger, complex systems||More expensive than MPPT controllers Typically shorter lifespan due to more components|
|Best for||Those with smaller systems (small homes), those living in warmer climates||Those with larger systems (cabins, homes, cottages), those living in colder climates|