Solar technology is gradually replacing traditional sources of energy. Industries and individuals are realising the advantages of using a renewable source of energy over expensive non-renewable sources. Most solar energy systems are equipped with inverters and batteries to store any surplus energy produced during the day for later use. However, batteries can get overcharged if not monitored.
A solar charge controller addresses the above challenge and is responsible for managing the power that goes into the batteries. It makes sure that the deep cycle batteries do not get overcharged or the power does not flow back to the panels at night. Now that we know what solar charge controllers do, let’s find out some more details such as their types and solar charge controller price.
Chargers are available in many variants based on power ratings, features and prices. However, the variants can still be broadly categorised as Pulse Width Modulation (PWM) and Maximum Power Point Tracking (MPPT).
PWM Solar Charger
A PWM solar charger directly connects the solar array to the battery bank. In the case of bulk charging, the array output voltage is switched down to the battery voltage. The voltage of the battery increases as it gets charged. Consequently, the voltage output of the panel increases as well, consuming more solar energy in the process. Thus, one needs to ensure that the voltage of the battery bank matches the nominal voltage of the solar array.
A higher voltage is needed to charge a battery. If the solar panel and the battery are at the same voltage, the battery will not charge. The PWM solar chargers are cheap and are often used in households and for commercial applications. Further, the PWM chargers have been used for a long period and still are a popular choice for many. However, a PWM controller operates below the maximum power voltage, even with a bit of voltage array.
Ideal Panel for a PWM Controller
An ideal panel for a PWM controller has a voltage above the mark needed for charging the battery. For instance, a panel with a maximum power voltage (Vmp) of around 18V will require a 12V battery to charge.
An MPPT controller is an efficient DC to DC converter that maximises the power output of a panel. Compared to PWM controllers, MPPT controllers are more sophisticated. They can manipulate the input voltage as well as the current of the PV array to adjust to the optimum operating voltage, ensuring maximum power generation at any moment.
Interestingly, MPPT controllers may also be coupled with higher voltage PV arrays that are above nominal voltage. It allows the user to opt for one of the many types of solar PV panels; that may cost less or offer more flexibility in terms of size. Higher voltage arrays also mean fewer strings in parallel causing lower array current, fewer combiner box fuses and less voltage drop. Thus, smaller wires can be used, enabling the MPPT controllers to save money by reducing costly copper wiring.
Ideal Panel for an MPPT Controller
It is recommended to check the following while choosing a match for an MPPT controller:
- Ensure the panel’s open-circuit voltage (VOC) is under the permitted voltage.
- For the controller to trigger, the VOC must be above the threshold or the start voltage.
- The maximum panel short circuit current (ISC) must be under the specified range.
- The maximum array wattage must also be kept in check.
However, keep in mind, while the MPPT technology is more expensive than the PWM, it may not always be the best or better choice between the two. Choosing a PWM or an MPPT solar charge controllerwill depend on the user’s location and application.