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What is a Solar Charge Controller

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Solar Charge Controller in Solar Power SystemA solar charge controller manages the power going into the battery bank from the solar array.  It ensures that the deep cycle batteries are not overcharged during the day, and that the power doesn’t run backwards to the solar panels overnight and drain the batteries. Some charge controllers are available with additional capabilities, like lighting and load control, but managing the power is its primary job.

A solar charge controller is available in two different technologies, PWM and MPPT. How they perform in a system is very different from each other. An MPPT charge controller is more expensive than a PWM charge controller, and it is often worth it to pay the extra money.

PWM Solar Charge Controller

A PWM solar charge controller stands for “Pulse Width Modulation”. These operate by making a connection directly from the solar array to the battery bank. During bulk charging, when there is a continuous connection from the array to the battery bank, the array output voltage is ‘pulled down’ to the battery voltage. As the battery charges, the voltage of the battery rises, so the voltage output of the solar panel rises as well, using more of the solar power as it charges. As a result, you need to make sure you match the nominal voltage of the solar array with the voltage of the battery bank. *Note that when we refer to a 12V solar panel, that means a panel that is designed to work with a 12V battery. The actual voltage of a 12V solar panel, when connected to a load, is close to 18 Vmp (Volts at maximum power). This is because a higher voltage source is required to charge a battery. If the battery and solar panel both started at the same voltage, the battery would not charge.

A 12V solar panel can charge a 12V battery. A 24V solar panel or solar array (two 12V panels wired in series) is needed for a 24V battery bank, and 48V array is needed for 48V bank. If you try to charge a 12V battery with a 24V solar panel, you will be throwing over half of the panel’s power away. If you try to charge a 24V battery bank with a 12V solar panel, you will be throwing away 100% of the panel’s potential, and may actually drain the battery as well.

PWM Charge Controller Systems

MPPT Solar Charge Controller

An MPPT solar charge controller stands for “Maximum Power Point Tracking”.  It will measure the Vmp voltage of the panel, and down-converts the PV voltage to the battery voltage. Because power into the charge controller equals power out of the charge controller, when the voltage is dropped to match the battery bank, the current is raised, so you are using more of the available power from the panel. You can use a higher voltage solar array than battery, like the 60 cell nominal 20V grid-tie solar panels that are more readily available. With a 20V solar panel, you can charge a 12V battery bank, or two in series can charge up to a 24V battery bank, and three in series can charge up to a 48V battery bank. This opens up a whole wide range of solar panels that now can be used for your off-grid solar system.

MPPT Charge Controller Systems


Watch our video on what a solar charge controller is and how to size it for an off grid solar power system here:

 

Also, check out our video on the differences between PWM and MPPT Charge Controllers:


The Key Features of a Solar Charge Controller are:

  • Multistage charging of battery bank - changes the amount of power set to the batteries based on its charge level, for healthier batteries.
  • Reverse current protection - stops the solar panels from draining the batteries at night when there is no power coming from the solar panels.
  • Low voltage disconnect - turns off attached load when battery is low and turns it back on when the battery is charged back up.
  • Lighting control - turns attached light on and off based on dusk and dawn. Many controllers are configurable, allowing settings for a few hours or all night, or somewhere in between.
  • Display- may show voltage of battery bank, state of charge, amps coming in from solar panel.

Shop for a solar charge controller among these great brands, now!

Or, call us today at 877-878-4060 to see which solar charge controller is best for your application!

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