MPPT is an automatic algorithm that utilizes Maximum Power Point Tracking technology to get the maximum power from solar modules. This is the main difference between the PWM and the MPPT controller. The PWM or Pulse Width Modulation controller acts as a switch that turns on and off the connection to protect the battery.
Tracking Technology is just one of the benefits of the MPPT. We have listed 9 other reasons to pick the MPPT over the PWM controller.
1. More Amps
The main reason you would go for a MPPT over PWM is for greater power. MPPT stands for Maximum Power Point Tracking. The Controller tracks the voltage of the panels adjusting it to deliver up to 30% more power from the Solar Panels to the Batteries.
This is because a MPPT Controller acts a DC to DC transformer in that in takes in a high Voltage reduces the Voltage but maintains the power therefore increasing the Current. The PWM Controller is just a switch that connects the Solar Panel to the Battery and protects the battery from overcharge by connecting and disconnecting at the absorption stage.
Both will perform the same function but one just does it efficiently while delivering more power.
2. Better Design and Technology
Manufacturers have invested more in improving MPPT controllers over the years than they have in PWM Controllers. All the updates on controllers can be mostly found in MPPT Controllers with PWM controllers remaining unchanged over the years. From basic applications of heat sink designs for heat dissipation to the more complex Bluetooth applications these features can be only found on MPPT Controllers.
Take Renogy for Example they have both PWM and MPPT controllers but you can clearly tell they put more effort in MPPT controllers than they do the PWM controllers.
This favoritism is not only because of the Technology behind the controllers but rather because the system sizes for the controllers. MPPT controllers are mostly used in big solar arrays while PWM for small PV Systems. As they say with greater power comes greater responsibility the more the amps the more the heat, price and therefore the need for added features.
3. Compatible with Lithium Batteries
If you looking to set up a battery bank with lithium batteries, MPPT is the only way you can go as PWM controllers don’t have the technology to charge lithium batteries. While other battery types move through bulk, boost and float modes Lithium batteries are just built differently.
Lithium Batteries may just use bulk mode until a target voltage is achieved. You may set for absorption mode for a couple of minutes before going to float. But it is possible to go straight from Bulk to float.
Some MPPT controllers also have a feature where they can charge an over-discharged lithium battery. The Protection Circuit of Lithium batteries will turn off the battery when it’s discharged rendering it useless. A controller with a wake-up feature will send small charge current to reactivate the protection circuit.
4. Custom profile for Batteries
While both MPPT controllers and PWM controllers have parameters set for SLA, AGM and Lead Acid batteries for the newer lithium batteries like Tesla Batteries which required different settings you won’t be able to charge them with PWM controllers.
MPPT Controllers allow you to dial in control parameters like charge limit and over-voltage disconnect for any batteries.
5. Can Wire in Series
MPPT Controllers allow you to wire you Solar array in Series whereby in PWM Controllers you can only wire the panels in parallel.
N/B It is possible to wire Solar panels in series with PWM controllers however this is not recommended for as it can easily heat up.
6. Better performance in cloudy days
Because the MPPT controller is always tracking the maximum power point it can react quickly to changes in the input Voltage. This includes when there are passing clouds which can read to a drop in voltage.
In PWM systems it will take some time for it adjust accordingly once the clouds pass. Meaning you will get more power from the MPPT than PWM in cloudy conditions.
7. Temperature Regulation
MPPT controllers have a Temperature Sensor that monitors the battery temperature and makes adjustment to ensure compensation of control parameters. The Temperature Sensor may come separately with some MPPT controllers but it is an essential part to ensure it adjusts according to the Battery temperatures.
8. Remote Monitoring
MPPT Controllers have options of Remote monitoring that give information on what is happening in the system. This may include the input voltage, output voltage, input current, output plus information about the battery including the Battery Voltage and Temperature.
Most controllers in the market are compatible with MT-50 Remote meter that can give you information on how the system is performing. It also allows you to enter custom parameters for your controller.
Other MPPT controllers like the Victron have Bluetooth Modules that can connect to you phone where you can view the performance and make changes to parameters. This is important as most solar panels systems are stored in battery compartments that are not easily accessible or away from a living area.
9. Software and Applications
An MPPT Controller like the Renogy Series Controllers come with a PC Communication cable that can be hooked up to your computer. This allows for monitoring but you can also set parameters through Software provided by the Company.
The Victron also has a android phone application that is user friendly and gives a lot of data on what is happening on the controller. The data includes power, voltages, input and output current and also includes historical performances. You can also export the data on a CSV file.
Some MPPT Chargers will routinely (once a month) apply an equalizing charge. This is intentionally overcharging Lead Acid batteries to remove sulfate crystals that build up on the plates over time.
There are still options where you may consider PWM controllers over MPPT Controllers. MPPT Controllers don’t come cheap and if you have a small solar system where the extra efficiency is not necessary you may forgo the MPPT Controller.
Also, PWM controllers provide the necessary protection for your battery which is the main purpose for the controller.