MPPT VS PWM Solar Controller
Here we discuss the difference between a MPPT and PWM Solar Controller and the benefits of each one.
What is a Solar Regulator?
A Solar Regulator or Solar Charge Controller, is essential if you have a solar system with batteries. The job of the solar regulator is to regulate the power from the solar panels to the batteries, so you don’t overcharge your batteries. Overcharging batteries can reduce battery life as well as affect their performance. The solar regulator can also detect when there is no charge coming from the solar panels and stop reverse charging from the batteries to the solar panels. MPPT and PWM are both energy control methods.
How PWM works
PWM (Pulse Width Modulation) slowly lowers the amount of power going into the batteries as they get closer to full charge. The PWM controller is basically a restrictor valve that connects your solar panels to your batteries, and pulls the voltage of the panels down to that of your batteries. The PWM controller allows the batteries to be fully charged without adding any stress to the battery, so it lasts longer.
How MPPT works
The MPPT (Maximum Power Point Tracking) controller will adjust its input voltage to gain maximum power from the solar panels, and then convert this power to provide the different voltage needed for the battery. This means that you can have a 12V battery on one side of the MPPT controller and a large number of solar cells wired together to produce 36V.
MPPT vs. PWM
Charging Efficiency – An MPPT regulator helps reduce power loss, as it essentially converts the excess voltage into additional amps. Using an MPPT controller allows for higher voltages from the panels to the solar charge controller. Compare this to the PWM regulator where the voltage from the solar panel has to be 18V to charge 12V batteries.
Applications – One of the drawbacks of PWM is that the solar input voltage must match the battery bank voltage. If you want to use a grid tied system, you can only use a MPPT controller as PWM cannot be used with higher voltages.
Size of the system – MPPT controllers let you have a larger solar panel array with higher input voltage than the battery bank. MPPT controllers allow you to have more flexibility in your system growth. PWM controllers have limited capacity for system growth.
Warranty – MPPT controllers typically have longer warranties, but PWM technology has been around for longer.
Durability – PWM controllers are durable and come with passive cooling systems.
Cost – MPPT controllers are more sophisticated and can cost as much as double that of a PWM controller.
When to choose a PWM vs. MPPT controller
The PWM controller is a good option for:
- Smaller systems
- Efficiency of the system is not critical
- Solar cell temperature is around 45°C – 75°C
The MPPT controller is best for:
- Larger, higher power systems
- When the solar voltage is significantly higher than the battery voltage
- When the Solar cell temperature is below 45°C or above 75°C