Getting Started with Solar Charge Controllers: A Beginner's Guide

Charge controllers are essential to your solar power system. You have to take into consideration whether you're using a PWM (Pulse Width Modulation) or an MPPT controller. At SanTan Solar, we carry MPPT charge controllers, these will be the primary discussion of this blog. 

An MPPT (Maximum Power Point Tracking) Charge Controller is one that can deliver the best performance when it comes to charging your batteries. It manages the charging of your batteries from the solar panels by converting a high voltage produced by your array to a lower voltage that your batteries can accept. Any unused voltage will be converted into amps so there is no power loss. Charge controllers are made to block any reverse current and prevent battery overcharge. The MPPT charge controller by design converts the higher voltage down to the lower voltage. 

In order to check if the charge controller works for your system, divide the total wattage of your solar array by the voltage of your battery bank. This can give you a starting point to size the amp rating your charge controller will be. This is explained in more detail later in this article. When it comes to sizing your system properly, there are several primary rating factors that need to be considered. First is what battery voltage the controller is made to work with. 

The second rating would be the voltage input. Keep in mind that any charge controller would have a minimum and maximum system voltage limit that it can handle from the solar module array. It's important that you make sure there is no condition that the solar module array voltage will go above this limit or you could potentially harm the controller. You want to make sure that the open circuit voltage (VOC) of the solar array does not go above this value. This includes accounting for environmental conditions that would affect the voltage, then adding 25% environmental factor which is 131V (35VOC x 3 in series x1,25 - 131.25V). This is fine for a charge controller that can handle up to 150V maximum. 

The last factor is amps. Amps are another value you'll have to pay close attention to for your charge controller. 

Here is a very basic formula for power as a starting point in Watts:

Power = Volts x Amps

Here we know the power is 3,000 Watts, and the battery bank is 48 volts, so:

3,000 Watts - 48 Volts x Amps

This will give us:

Amps = 3,000 Watts / 48 Volts

Amps = 62.5A

So, a charge controller that could handle between 60A to 70A is possible. Always check with your charge controller manual to be sure. It is possible to "over-panel" a charge controller, where you put a higher wattage into the charge controller than it is rated for. During the peak output, the charge controller will "clip" the output, but the rest of the day, when the output drops lower than its amp rating, it will generate the full output. 

In conclusion, MPPT charge controllers are your best options to get the most power from your solar panels. Check us out online at www.santansolar.com or call us at either of our showroom locations!
Check out our selection of charge controllers here!