Solar charge controllers are devices installed in a solar PV system to control the charging of solar batteries. They prevent the solar battery from overcharging or over-discharging under different circumstances. There are two charge controllers; Pulse with Modulation (PWM) and Maximum Power Point Tracking (MPPT).
These two devices balance the voltage and current between the solar panel and the solar batteries. Since PWM and MPPT perform the same function, can they be used in the same Solar PV system?
To determine if PWM and MPPT can be mixed in one solar system, we will discuss how each works and what makes them different. We will also discuss the most efficient between the two in the guide below. Stick around.
Can I Mix PWM and MPPT charge controller?
Each solar PV system needs a charge controller connected to it. These devices balance the voltage and current between a solar battery and solar panels. They also ensure the solar battery does not overcharge if the sun is hot and over-discharging during a cloudy day. PWM and MPPT are the two classifications of solar charge controllers.
These two devices operate differently, which makes them practical for various reasons.
PWM charge controllers act as a switch that turns on and off to acquire the voltage required to charge the solar batteries. This device balances the voltage and the current of the solar battery and the solar panel. When the battery is charging, PWM reduces the current slowly.
MPPT charge controller matches the solar batteries’ voltage and the solar panel to ensure the charging is maximized. This technique provides the solar battery discharges at a lower rate when the weather is cloudy.
MPPT also ensures the solar battery utilizes the maximum solar energy when the sun is hot. This means with this device, the voltage and current are not equal. The device acts following the circumstance at hand.
To determine if you can mix the two solar charge controllers, we will discuss the main differences between the two techniques below.
Which charge controller is better, MPPT or PWM?
Both MPPT and PWM perform the same function but in different magnitude.
A PWM or the Pulse with Modulation ensures the voltage between the solar panel and the solar battery is equal. For this reason, PMW tends to be a little inefficient for large-scale solar energy usage. How, you ask?
Since the voltage between the solar battery and the solar panel must be equal, the device cannot protect the battery from discharging in cloudy weather conditions.
An MPPT, on the other hand, is efficient for large-scale solar usage. The device acts following the situation at hand.
If the sun is in scarcity, the device will limit the amount of energy being used. This prevents the solar battery from discharging. Once the sun is back and the solar panel is harvesting more solar energy, the devices enable more energy output.
In terms of prices, MPPT is more efficient, making it cost more than PWM. MPPT charge controllers increase the charging by at least 40% more than PWM.
Due to those reasons, if you are using solar energy for small projects such as light bulbs, PWM will be efficient. However, if you power many devices, MPPT is the most effective.
Can I connect two charge controllers on the same solar panel?
You can connect two charge controllers to one solar panel.
This, however, depends on the amount of power you use at your home. If your solar PV system does not power many appliances, one charge controller will fulfill the purpose effectively. Furthermore, an MPPT is 40% more effective than PWM.
There are some advantages of operating two charge controllers on one solar panel.
- Each charge controller will detect a different voltage depending on its capability. For this reason, charging is maximized.
- In case of the sun is hot, the charge controllers will detect the excess current coming from the solar panel and stop any more from entering the solar battery. This prevents the solar battery from overcharging.
- If you have a large solar panel, having two charge controllers will increase your solar panel’s efficiency and increase the lifespan of the solar PV system.
Although you can connect two charge controllers to one solar panel, make sure the controllers are the same size. Otherwise, the powerful charge controller will be derated to the same level as the smallest charge controller.
Can you use 2 MPPT controllers together?
You can use two or more MPPT controllers in one solar panel or even more solar panels. However, you should consider the size of the charge controllers.
If your solar panel is large and too powerful, you might consider adding more charge controllers. However, it would be best to ensure the charge controllers were of the same size. If one charge controller is more powerful than the other, the more robust controller will be derated.
Although the 2 MPPTs are connected to one solar panel, they will always detect different voltage readings from the solar battery. This will make each charge controller operate independently.
Installing a charge controller in your solar PV system will save you a lot of frustration. A charge controller will prevent the solar battery from discharging when the condition is not conducive to charging. Charge controllers also limit the solar battery’s current when the sub is too hot.
Solar charge controllers are subdivided into PWM and MPPT.
A PWM, which stands for Pulse With Modifications, acts as a switch between the solar battery and the solar panel. This device balances the voltage and current between the solar panel and solar battery. If the current flowing from the solar panel is high, the output increases.
An MPPT charge controller, which also stands for Maximum Power Point Tracking, is efficient for large-scale use. If the sun is too hot, then the MPPT charge controller stops any current from reaching the solar battery. MPPT is 40% more efficient than PWM.
You can connect two or more charge controllers to a single solar panel. You should, however, ensure the two charge controllers are of the same size. Using charge controllers with different capabilities will lead to the powerful one being derated.
Eng. Matthew Joseph Nandirio is the Founder of walkingsolar.
After graduating from the University of Houston in 2002, matt started working as an electrical and electronic engineer for several multi-national solar energy companies.
He has a wide range of experiences including solar system requirement analysis, planning, maintaining, debugging and even solar device development through research.
He now shares his 20 years of expertise through his articles on the walkingsolar website.
Further, he is also the author of two books on Solar Technology, “Solar Power for Villages” and “DIY Solar System for Dummies”.