What a Solar Charge Controller?

Posted by sere on March 9th, 2020

Do you need a solar charge controller? A solar charge controller, also called a solar regulator is fundamentally a solar battery charger connected between the solar panel/s and battery powered. Its job would be to control the battery charging process to ensure the battery is charged properly, or more importantly, not over-charged. DC combined solar charge controllers, as shown in the diagram below, have been in existence for decades and are employed in almost all small scale off-grid solar energy systems.

Normally, most smaller charge controls up to 40A in size are used for easy caravans, RVs and camping possess the DC load output springs built-in. But, most larger, more powerful MPPT solar charge controllers do not have load output signal terminals since they are specifically intended for large solar arrays and coupled with powerful off-grid inverters.

There are two main kinds of solar charge controllers, PWM and MPPT together with the later being the key focus of the article because of the increased charging efficiency many different advantages explained in detail below.

The switch is open until the battery reaches the absorption charge voltage, then the switch begins to open and close rapidly (hundreds of time per second) to reduce the current flow and maintain a constant battery voltage. This works fine, but the problem is that the solar panel voltage is pulled down to match the voltage. This brings the panel voltage from its best operating voltage and reduces performance.

PWM charge controls continue to be a fantastic low cost alternative for small systems where a tiny solar panel is used for simple applications like solar light, camping and basic items like USB/phone chargers.

Using this clever technology MPPT solar charge controllers may be up to 40 percent more efficient depending on the battery voltage and type of solar panel connected. The reason for the increased efficacy and how to correctly size a MPPT charge control is explained in detail below. As a general rule MPPT charge controllers should be utilized on all higher power system with 2 or more panels or if the lens voltage is a lot greater than the battery voltage.