Solar energy

The solar charge controller

Solar charge regulators: functions, types of regulator, characteristics, and selection guide

Table of content

  • what is the solar charge controller?
  • Functions of the solar regulator 
  • How to choose a solar charge regulator? 
  • The Mppt & Pwm solar charge regulator

what is the solar charge controller?

The solar regulator (also called charge regulator or charge), regulates the level of energy stored by the batteries in order to avoid overcharging or over-discharging of the batteries : 

  • It limits, sees stops, the charging of the solar battery by the solar module

when the battery is fully charged;

  • It slows down the discharge by unloading the use, even see the total stop,

To avoid deep discharges that could damage the batteries.

The solar controller continuously displays the operating status of the photovoltaic module and the state of charge of the solar battery. This display is done either via « LEDs » or via a digital screen.

It is a completely autonomous device, which performs all the operations of load measurement and correction automatically.


  1. charge level display
  2. display of incidents (overload, deep discharge, short circuit)


To choose your solar regulator, you have to consider three main elements :

  1. overload protection
  2. protection against deep discharge
  3. Short-circuit protection
  4. Protection of photovoltaic solar panels (against charge returns electric)
  5. Thermal protection

Some more efficient solar regulators offer « functions « integrated or optional »:

  1. – Room temperature compensation to measure the battery charge
  2. – Wired or remote connection to a PC or computer network
  3. Triggering of automatically programmed alarms (audible signal, e-mail, SMS)
  4. -Recording for analysis of data from the regulator etc …
  5. The maximum open-circuit voltage of the panels: The regulators accept more or less wide voltage ranges.
  6. The minimum voltage to charge the batteries.
  7. the maximum intensity of the regulator: the intensity of the regulator (expressed in amps) must be greater than the short circuit intensity of the solar panels to which it is connected.
This data is indicated on the notice for each panel. It’s better to
add take a safety margin of 10% to 20%.


A new generation of regulators has appeared: MPPT solar regulators (for Maximum Power Point Tracking), which means finding the PowerPoint maximum).

This new technology makes it possible to obtain the best performance from photovoltaic solar panels, from 10% to 25% more energy.
An MPPT solar regulator has a scanning function, which traverses the voltage of the solar panel every two hours to find the power outlet maximum: thus it can adapt the voltage delivered by the panel to that which the solar batteries can absorb.

These regulators not only increase the energy production of a photovoltaic installation but by optimizing the battery charge, they also significantly extend the life of these batteries.

The MPPT regulator, more expensive than these PWM colleagues, will be able to modify the module voltage and supply the voltage needed to charge at 100% of batteries.

The charge regulator must be chosen according to the current delivered by the solar panels and the voltage of the battery bank:

  • for a PWM regulator, the regulator must be able to operate on the battery bank voltage; the regulator current must be at least 1.5 times the short-circuit current of the solar panels;

  • for an MPPT regulator, the regulator must be able to operate on the battery bank voltage; the power of the solar panels must be less than or equal to the power acceptable by the charge controller; the voltages Voc and Vmp of the solar panels must be lower than the voltages acceptable by the charge regulator;

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