What Does a Solar Charge Controller Do?
A solar charge controller regulates the amount of voltage and current that is supplied to your batteries from your solar array. Voltage levels will vary significantly throughout the day as the sun’s position, cloud cover, and other environmental conditions vary. Connected between your solar array and batteries, the charge controller is essentially a battery charger that ensures the proper amount of voltage is safely applied to your batteries. It also reduces the voltage to a trickle charge (float voltage) to prevent overcharging when the battery is full.
Types of Solar Charge Controllers – MPPT vs PWM
MPPT solar charge controllers have become the modern standard for most solar systems. They convert all of the energy produced by the solar panels to useable levels for efficient battery charging. Modern solar panels generate higher voltages than legacy solar panels. MPPT controllers convert the excess voltage to a lower voltage, but at a higher current (more amps).
PWM solar charge controllers have been the standard for decades. They are less expensive compared to MPPT controllers and still work well when the solar panel output voltage matches the battery bank voltage (e.g. 12-18v solar array charging 12v battery bank). PWM controllers can also be used higher voltage panels (20 volts and higher) but with limitations. If the solar panel voltage exceeds the rated voltage of the controller, then only a portion of the power from the high voltage solar array will pass through a PWM controller to your battery bank.
How to Choose the Right MPPT Solar Charge Controller?
MPPT solar charge controllers are rated by Maximum Input Voltage and Maximum Output Current (Amps). So you need to determine the maximum voltage and current limits of your solar array.
Start by checking the maximum voltage (Voc) and maximum current (Imp) of your panel(s). The ratings sticker on the back of the solar panels has the information you need. Also make note of your battery system voltage (12, 24, or 48 volts).
Enter the information into this worksheet to calculate your total solar output and get an MPPT solar charge controller size recommendation.
Find an MPPT Solar Charge Controller with these specs.
The controller voltage and current ratings should be higher than Calculated Input Voltage and Output Current shown above.
Victron controllers have the input voltage and output current rating in the name. Example: a Victron Smart MPPT 100 | 50 controller has an input voltage of 100V and an Output Current of 50A.
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