Solar charge controllers
A solar charge controller is an essential electronic component of every solar PV system.
It is placed between the solar array and the battery storage bank in the system.
The main function of a standard charge controller can be summarized as:
- Preventing back current that flows from batteries to PV modules when the PV voltage is less than batteries.
- Preventing overcharging of the batteries when the voltage of the PV panels is higher than that of batteries
- Connecting DC loads to Battery bank
While Small PV systems operating with low power output can be a function without using charge controllers, for stand-alone systems that ensure a long-term operation, charge controllers have to be used to prevent overcharging or deep discharging of the batteries in a battery bank during its operation.
The core operation of a charge controller is to control the output power of the solar panel to the batteries and divert the extra power from the fully charged batteries by burning off excess power as heat while returning the power produced from PV panels to the batteries when they are depleted of their electric energy.
MPPT charge controllers
MPPT or Multiple Power Point Tracking charge controller is a modern technology in solar industry and is now becoming one of the main components of every solar PV system. It is an electronic component that works with PV modules allowing them to produce their maximum power output efficiency. MPPT is used in conjunction with ordinary trackers in a PV system, but each has their own functionality. While the function of a tracker is directing a solar module towards the sunbeam to physically track the sun and receive the maximum available solar energy during the day, the function of an MPPT is to electronically track the sun and vary the electrical operating point of the modules so that they can deliver their maximum power.
Despite different methods used in MPPT designs, the most commonly used method is changing the actual input voltage in such a way that the maximum power is achieved. When a conventional charge controller charges a battery, it simply connects the solar module directly to the battery and forces the panel to work at the discharged battery voltage. This kind of operation wastes the power output of the panel. An MPPT charge controller rather follows the following steps:
- It calculates the voltage that the module is able to produce
- Then operates the modules at their maximum power voltage to extract their full power output
- It converts the maximum produced voltage of the panel to the voltage of the discharged battery through a DC-DC converter.
- Finally, it increases the charging current to the battery storage and therefore uses the maximum produce power of the solar panel that could have been otherwise wasted by a conventional charge controller
A combination of the physical tracking and electronic tracking of the MPPT charge controller greatly affects the performance of the charging operation by using the maximum available solar energy as well as the PV panels output energy.