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Solar charge controller : Basic function, Types and characteristics

By Energy Hamd - December 09, 2021

Solar charge controller : Basic function, Types and characteristics
Solar charge controller : Basic function, Types and characteristics


Solar charge controller : Basic function, Types and characteristics


        1.Description

    The charge / discharge regulator is associated with a photovoltaic generator, its role, among other things, to control the battery charge and limit its discharge. Its function is essential because it has a direct impact on the battery life.

    Several charge controller technologies are found on the installations:

  • All or nothing (TOR) regulation by electromechanical cut-off. This type of regulator is no longer marketed and is set to disappear.
  • PWM (Pulse Width Modulation) regulation with two types of coupling on the battery.
  • Direct coupling called PWM (Pulse With Modulation) regulator.
  • Coupling by impedance adapter called MPPT (Maximum Power Point Tracking) regulator.


        2. Basic function

            2.1. PWM regulation (Pulse Width Modulation)

    The regulator is inserted between the photovoltaic field and the battery. It is composed of an electronic switch operating in PWM (Pulse Width Modulation) and a non-return device (diode).

    The opening and closing of the electronic switch takes place at a certain frequency, which makes it possible to regulate the charging current according to the state of charge with precision.

  • When the battery voltage is lower than the regulator limiting voltage, the switch is closed. The battery is then charged with the current corresponding to the sunshine. We are in the "Bulk" phase.
  • When the battery voltage reaches a predetermined regulation threshold, the switch opens and closes at a fixed frequency to maintain an average current injected into the battery. The battery is charged, we are in the "Floating" phase.

PWM regulation (Pulse Width Modulation)


NOTE: The PWM regulator can only work exclusively with 36 or 72 cell photovoltaic modules (12V or 24V).


            2.2. MPPT (Maximum Power Point Tracking) regulator

    The charge regulator is made up of a high efficiency switching DC / DC converter which performs three functions:

  • Detection of the maximum power of the photovoltaic field as long as the battery is not charged.
  • DC / DC conversion.
  • Regulation of the output voltage according to the charge phase (Bulk, Absorption and Floating).


NOTE : The DC / DC converter is used as a voltage step-down. This means that the MPP voltage of the photovoltaic generator must always be higher than the battery voltage.



    The solar field is connected to the input of the regulator and the battery to its output. When the battery voltage is lower than the regulation voltage, the regulator operates the photovoltaic generator at maximum power Pmpp and transfers this power to the output.

    By design, the MPPT regulator allows a production gain of 5 to 30% compared to a PWM regulator. This gain will increase in winter and during periods of low sunlight.

    The MPPT charge controller allows greater flexibility in the choice of panels. Indeed, all types of photovoltaic module can be used as long as one remains within the voltage (V) and current (A) tolerances of the regulator.


        3. Abstract

Properties

PWM regulator

MPPT regulator

Battery power

Direct coupling with the PV array

Direct coupling with the PV field Via a step-down converter

Relation between the voltage of the PV chain and that of the battery

They must be compatible

The voltage of the PV chain can be higher than that of the battery

Sizing of the PV array

Current (Battery charging current)

In power (Current * Battery voltage)

Section of PV cables

Fat

Mean






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