Introduction

A solar charge controller is fundamentally a voltage or current controller to charge the battery and keep electric cells from overcharging. It directs the voltage and current hailing from the solar panels setting off to the electric cell.

If you want to use solar to go completely off-grid, there are two types of charge controllers to consider Pulse Width Modulation (PWM) controllers and Maximum Power Point Tracking (MPPT) controllers. PWM solar charge controllers are the standard type of charge controller.

MPPT Charge controller

An MPPT, or Maximum Power Point Tracker is an electronic DC to DC converter that optimizes the match between the solar array (PV panels), and the battery bank or utility grid. Maximum Power Point Tracking is electronic tracking - usually digital. The charge controller looks at the output of the panels and compares it to the battery voltage. It then figures out what is the best power that the panel can put out to charge the battery. It takes this and converts it to best voltage to get maximum AMPs into the battery. Most modern MPPT's are around 93-97% efficient in the conversion. You typically get a 20 to 45% power gain in winter and 10-15% in summer. Actual gain can vary widely depending weather, temperature, battery state of charge, and other factors.

MPPT Charge controller is a technology that is specifically made to work with virtually all the photovoltaic. Certainly, it’s for the solar unit wherein module voltages are higher than the battery voltages. It’s an electronic system that assists the solar module produces all the power, which they are able to.

PMW Charge Controller

Pulse Width Modulation (PWM) solar charge controllers PWM solar charge controllers are the standard type of charge controller available to solar shoppers. They are simpler than MPPT controllers, and thus generally less expensive. PWM controllers work by slowly reducing the amount of power going into your battery as it approaches capacity.

The PWM controller is in essence a switch that connects a solar array to a battery. The result is that the voltage of the array will be pulled down to near that of the battery.

With a PWM controller the current is drawn out of the panel at just above the battery voltage, whereas with an MPPT controller the current is drawn out of the panel at the panel “maximum power voltage” (think of an MPPT controller as being a “smart DC-DC converter”)

A PWM (Pulse Width Modulation) controller can be thought of as an (electronic) switch between the solar panels and the battery:
⦁ The switch is ON when the charger mode is in bulk charge mode.
⦁ The switch is “flicked” ON and OFF as needed (pulse width modulated) to hold the battery voltage at the absorption voltage.
⦁ The switch is OFF at the end of absorption while the battery voltage drops to the float voltage.
⦁ The switch is once again “flicked” ON and OFF as needed (pulse width modulated) to hold the battery voltage at the float voltage.