Solar charge controllers are designed to do two primary things within a solar power system: optimize the charging of your deep cycle batteries by the solar panels and prevent electricity from the batteries from going through the solar panels when there is no sun.
Many we offer have additional features, including the ability to automatically turn DC powered loads off or on, such as lights. Others may be used with relatively high voltages of strings of solar panels. Additionally, some can provide monitoring of your batteries' voltage and amp-hours left and even connect to your home data network for remote monitoring.Read more +
How Do Solar Charge Controllers Work?
Solar charge controllers are specified by both amperage and voltage. You will need one that can support the voltage of your solar panel array, and then output to the battery bank's voltage (usually 12, 24 or 48VDC). Next, you'll want to make sure the solar charge controller has enough capacity to handle the current (in amps) from your solar panel array. Take the wattage of your solar panels and divide it by the battery bank's voltage to get a rough estimate of how many amps the controller needs.
The basic formula for sizing one is to take the short circuit current (Isc) of the array and multiply it by 1.56. Be sure that the solar controller you select can handle at least that many amps.
Be sure to protect this important part of your system with appropriate overcurrent protection before and after the solar controller (see Enclosures, Electrical & Safety for options).
What is PWM & MPPT?
Now that you know what size solar controller to look for, identify which type of solar charge controller is right for your application: MPPT or PWM.
MPPT Solar Charge Controllers
The MPPT (Maximum Power Point Tracking) solar controller is the shining star of today's solar systems. These controllers actually detect the optimum operating voltage and amperage of the solar panel array and match that with the battery bank. The result is additional 15-30% more power out of your solar array versus a PWM solar controller. Although the MPPT solar charge controller is more expensive than its PWM counterpart, it is generally worth the investment for any solar electric system over 200 watts.
PWM Solar Charge Controllers
A PWM (Pulse Width Modulated) solar charge controller is the traditional style. They are robust, inexpensive and widely used in solar panel applications. PWM shunt controllers are used less often and mostly in applications where electrical interference is an issue.
Once you have decided on a type of solar charge controller, you'll want to identify what features you need. There are many basic solar charge controllers that work well. In addition, there are some great features that will make your renewable energy experience even better. One important addition to your system is Battery Temperature Sensors. Battery capacity depends on temperature, therefore proper battery charging can be significantly enhanced with a temperature sensor.
Additionally, some solar controllers offer adjustable control voltage set points, low voltage disconnect, overload protection and metering. If you plan to run a DC load, you can connect it directly to the solar charge controller. If the solar controller is equipped with a low voltage disconnect (LVD), then the solar charge controller can detect when the battery is low and shut off the DC load until the battery is charged.