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Solar Charge Controller diagram

Solar Charge Controller

An essential part of every Off-Grid and Hybrid Solar Power System is the Solar Charge Controller.

In this starter guide we’re going to cover:

Let’s get started.

What Is A Solar Charge Controller

Victron SmartSolar MPPT 250/100
An MMPT Charge Controller

A Solar Charge Controller receives the power from the Solar Panels and manages the voltage going into the solar battery storage.

 Its primary function ensures that the deep cycle batteries don’t overcharge during the day  and at night it blocks the reverse current going back into the Solar Panels.

It also protects the batteries from any electrical overload, this is particularly important for panels that  produce more voltage  than what the battery can handle.

This component comes in two technologies, PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking), although they function the same they perform quite differently from each other. More about this below.

They can also come integrated into inverters, making it easier to install and run more efficiently because of this.


  • Multi-stage charging of the batteries
  • Reverse current protection
  • Built-in overload protection
  • Disconnects when the battery is low
  • A temperature sensor (optional)
  • Monitor, tracking the state of charge, Amps and battery voltage (optional)

How Do Charge Controllers Work

Sometimes referred to as a Solar Regulator or simply a Solar Controller, this component sits between the solar panels and the battery bank. It  continuously monitors and regulates the voltage going into your battery bank .

Solar Controller Diagram

The energy from your Solar Panels are in the form of volts, this voltage can fluctuate depending on the amount of sunlight you receive during the day, this can be  detrimental to your battery  if it is  above the battery voltage .

When the battery has been charged fully it can no longer store any incoming energy, if the battery voltage gets too high it will rapidly degrade, overheating and become a  fire hazard .

Most of the latest charge controllers have overload protection built-in, much like a trip switch, it will protect against any faulty appliances or short circuits.

Voltage Regulating

To prevent the excess voltage which causes damage to your batteries the Solar Charge Controller regulates the flow of energy, what this basically means is that the controller  constantly checks the voltage  and increases or decreases the current depending on the level of the battery.

If you can imagine a glass of water being filled, when the glass is almost full we  slow down the rate  of the pour.

When there is an increase in electrical usage and the battery is being depleted at a faster pace the controller will allow the maximum charge possible to keep up with the demand.

The Different Types Of Charge Controllers

There are many types, sizes and manufactured Solar Charge Controllers on the market today. Each type comes with their own specific functions depending on your specific Solar Power System setup.

There are two main variations that Charge Controllers come in:

PWM (Pulse Width Modulation)

PWM Solar Charge Controller

The PWM controller is fundamentally the same as we explained above, it holds the voltage constantly to a safe maximum until the battery reaches full charge.

When fully charged the controller will drop the voltage and trickle the charge to such a rate that it simply keeps the battery “topped up”.

This type of controller has been around for many years in Solar Power Systems, it is an established technology which is inexpensive, however, there are drawbacks.


  • Time-tested technology
  • Affordable
  • Long lasting
  • Comes in a variety of sizes


  • Not expandable and limited for growth

MPPT (Maximum Power Point Tracking)

MPPT Solar Controller

 The MPPT controller is a more sophisticated technology  in that it will measure the VMP (Voltage at Maximum Power) of the panel and then  down-convert  it to the battery voltage.

Another advantage is the reduced power loss, the voltage running through the cables is higher,  this converts the excess into additional Amps. 

Note:  The more Amps into the battery the better. 

Modern MPPT Solar Charge Controllers are very efficient, around 93 – 97% energy conversion. In the winter months, you get from 20 – 45% power gain and in summer around 10 – 15%. This varies depending on factors such as temperature, weather, battery state, and other variables.

Many inverters for Grid-Tied and Hybrid systems now have integrated MPPT, the efficiency for these are around 94 – 97% making them ideal for easy installation and price.


  •  Increase in charge efficiency, up to 30% 
  • They can handle a higher array voltage than that of the battery bank
  • Sizes up to 120 Amps available
  • Longer warranties than PWM units
  • Flexible for system growth


  • More expensive than PWM controllers
  • Larger physical units

Which Charge Controller Is Best For My Setup?

This is a good question, the difficulty is it all dependant on your Solar Power system.

The  first thing to determine is what your Solar Panel array voltage output is , you will need to  ensure that your Solar Charge Controller can handle the capacity  to handle the current produced by your solar array. We have a guide on Solar Panels if you need to understand more about this component.

Typically 18V Solar Panels use a 12V controller but you can have other configurations such as 36V panels that will use a 24V controller and 72V panels use a 48V controller.

The next thing you will need to do is  divide the wattage of your solar panels by the battery bank voltage  to get an estimate of how many amperes the Solar Charge Controller requires.

The next thing to  determine is what battery type you will be using , you have two main battery types to consider, Lead Acid and Lithium-ion. To understand the different battery types you can read our Solar Battery Guide.

If you have a Lithium-ion battery like the PylonTech range you will have built-in surge protection.

High and low voltage with overload protection which prolongs the life of your battery which compliments the controller.

If you are looking for a separate Solar Charge Controller it’s always best to get advice from the professionals.

There are many variables to consider and buying one because it’s cheap or assuming it will fit your system will either cost you money or damage your other components.

To understand more we recommend watching this YouTube buyer’s guide video on Solar Charge Controllers

Do you have any questions about Solar Charge Controllers?

Comment below or contact us for more information and advice on buying the right one for your Solar system.


One comment

  1. Visitor Rating: 5 Stars

  2. Hi
    I have 15 x 140w Solar panels , I want to change my Charge controller , which of these are the best for my system: Victron Blue Solar 150/70 or the 250/60?

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