The charge controller regulates the DC energy from the solar panel and stabilizes it and creates a stable DC electrical energy for the charging of the batteries. In order to charge the batteries from a DC source, the charging current and voltage must be regulated constant. The voltage and current produced by the solar panel are not constant, so a charge controller is required for efficient charging of the batteries. Charge controllers also prevent reverse current flow from the battery to the panels and It protects the battery from overcharging. As a summary Charge controllers provides the followings:
*It protects solar panels by preventing reverse current flow from batteries to panels. *When the batteries are fully charged by the panels, it cuts off the power from the panels, preventing the batteries from overcharging. *Charges the batteries by fixing the voltage and current produced and variable in solar panels. This ensures that the batteries are charged efficiently. *It also prevents the batteries from over-discharging.The charge controller cuts off electricity from the solar panel when the battery is full.
The charge controller is a kind of DC-DC regulator. It provides more efficient charging of the batteries by fixing the voltage and current that cannot be produced continuously in solar panels.Batteries with a voltage of 12 V generally need around 14-14.5 V for a full charge. If the 18-20 V level voltage from the solar panel is not regulated, the battery will be damaged by overcharging.The controller regulates this high voltage by reducing it to the battery charge level.
It has two types. PWM and MPPT are charge controllers. The charge controller used in off grid systems is very important in terms of system efficiency.
PWM Charge Controller
PWM (Pulse Width Modulation) is an acronym for “pulse width modulation”. The PWM controller sends short charge pulses to the charged battery instead of a fixed output. The controller determines the length of the pulses and the transmission interval based on the charge state of the battery. If the battery is discharged, current pulses sent by the device to the battery are long and continuous. However, when the battery is charged, these pulses are sent at short intervals of a few seconds.
PWM is the most used controller in terms of being cheap in the solar energy industry. Although it is a very ideal system for small off-grid applications, MPPT is generally preferred in larger systems.
MPPT Charge Controller
MPPT (Maximum Power Point Tracking), which stands for “Maximum power point tracker”, charges the batteries by converting the electricity produced from PV panels to the most suitable voltage and current level for the operation of the system. This device monitors the voltage of the battery pack when the voltage value reaches a certain level and accordingly allows current flow from the panels to the batteries or cuts the charge.
The MPPT controller can convert overvoltage into current. With this feature, the time required to charge the batteries is shortened. This increases the efficiency of the system by ensuring that the system always works effectively.
Although the MPPT controller is more expensive than the PWM controller, the benefits, it provides to the system make the price difference insignificant. For this reason, MPPT control device is generally preferred in off-grid applications of 5kW and above.
Most of the inverters used now have charge controllers in their own. Although it usually changes according to the inverter capacity. Charge controllers between 12V / 24V / 48V and 50A / 60A / 70A / 80A are located inside the inverters. If the amount of current produced in the system exceeds the capacity of charge controllers in inverters, this problem can be solved by adding an external charge controller.
The wrong choice of charge controllers is one of the biggest causes of fires in photovoltaic solar energy systems. Because the circuit of the control devices that cannot carry the current coming from the solar panel is broken and loses its function. Then, it causes fire in solar panels due to the current flow from the batteries to the panels when the panel voltage drops. It can also cause the batteries to swell.