The power coming from the solar array into the battery bank is controlled by a solar charge controller. It prevents the deep cycle batteries from being overcharged during the day and prevents the batteries from being drained at night by power running backwards to the solar panels. Although some charge controllers come with extra features like lighting and load management, their main function is to manage electricity.
PWM and MPPT are the two available methods for solar charge controllers. They perform substantially differently from one another in a system. Even though an MPPT charge controller costs more than a PWM charge controller, doing so is frequently justified.
There are two principal types of solar charge controllers: PWM and MPPT. This article will mostly discuss MPPT due to its enhanced performance, higher charging efficiency, and other benefits, which are detailed below.
PWM Solar Charge Controllers
Simple PWM, or “pulse width modulation,” solar charge controllers employ a basic “quick switch” to modulate or control the battery charging and have a direct link from the solar array to the battery. Up until the battery achieves the absorption charge voltage, the switch (transistor) is open. The switch then rapidly opens and closes (hundreds of times per second) to control the current and keep the battery voltage constant. The issue is that the solar panel voltage is lowered to match the battery voltage, even though this works fine. As a result, the panel voltage is pulled below its ideal operating voltage (Vmp), which lowers the panel’s power output and operational effectiveness.
When one or two solar panels are utilized, PWM solar charge controllers are a fantastic low-cost alternative for tiny 12V systems, including straightforward uses like solar illumination, camping, and basic things like USB/phone chargers. Remember that if you utilize many panels, you should connect them in parallel rather than series.
MPPT Solar Charge Controllers
The solar panel can run at its maximum power point, or to be more accurate, the best voltage for maximum power output, thanks to MPPT or “maximum power point trackers,” which are significantly more sophisticated than PWM controllers. Depending on the battery voltage and operating voltage (Vmp) of the solar panel, MPPT solar charge controllers can be up to 30% more efficient using this innovative technology. Below, we go into further detail regarding the causes of the improved efficiency as well as how to properly size an MPPT charge controller.
As a general rule, MPPT charge controllers have to be utilized on any higher power systems utilizing two or more solar panels, or if the panel voltage (Vmp) is 8V or higher than the battery voltage – see further explanation below.
A maximum power point tracker, often known as an MPPT, is essentially an effective DC to DC converter used to maximize a solar system’s power production. A small Australian business called AERL created the original MPPT back in 1985, and today almost all grid-connect solar inverters and MPPT solar charge controllers employ this technology.
A solar panel’s voltage and current continually change throughout the day as a result of the fluctuating quantity of sunlight (irradiance) that strikes it. This is how an MPPT solar charge controller works.
An MPPT checks the panel voltage for the ideal ratio of voltage and current to produce the greatest power, in order to generate the most power. No matter what time of day it is or what the weather is like, the MPPT continuously monitors and adjusts the PV voltage to provide the greatest power. When compared to a PWM solar charge controller, the operating efficiency of this innovative technology improves and the energy output may be up to 30% higher.
PWM Vs MPPT Compared
The example below uses both a PWM and an MPPT charge controller to link a typical 60 cell (24V) solar panel with an operational voltage of 32V (Vmp) to a 12V battery bank. The power output is significantly decreased when using the PWM controller since the panel voltage must decrease to match the battery voltage. The panel can function at its peak power level and provide significantly more power with an MPPT charge controller.
NOTE: This Comparison highlights the problem with using a higher voltage solar panel on a 12v Battery Without MPPT