Charge Controllers

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Understanding Charge Controllers

Charge controllers come in many different shapes and sizes. Greenwired offers a range of controllers, from “simple” pulse width modulation (PWM) units that are designed to keep your batteries from overcharging,All the way up to the high tech Maximum Power Point Tracking (MPPT) units that modulate solar array voltage to maximize power output as well as provide automated functions for your battery bank.

When are charge controllers needed?

Any time you have a solar module (panel) hooked up to a battery bank for charging a battery, you will need to prevent the battery from overcharging using a charge controller.

A charge controller is unnecessary if your solar module connects solar directly to a load (fan or pump) or the grid.

What is a “simple” Pulse Width Modulation (PWM) charge controller, and when do you need it?

A PWM controller watches your battery for when it reaches a near charge setpoint, then slowly reduces the charging current to avoid overcharging the battery.

If you can answer YES to all of the following questions, than a PWM controller may be right for you. If not, look at the MPPT charge controllers below.

Is your solar array designed to charge one battery or a bank of batteries?
Is the distance from solar modules to batteries less than 50 ft (unless wire size is large enough to prevent voltage drop)?
Is the total solar array wattage less than ~450 Watts?
Is the panel voltage (or array voltage) correct for battery bank? (See table below.)

Nominal Battery Voltage
12
24
48

Suggested Vmp for solar module
17 to 21
34 to 38
64 to 68

What is a Maximum Power Point Tracking (MPPT) charge controller, and when do you need it?

A PWM controller monitors your battery so that when the battery reaches a near charge set point, the PWM controller slowly reduces the charging current to avoid overcharging the battery.

A PWM controller may suit you if you can answer “Yes” to all of the following questions:

Is your solar array designed to charge one battery or a battery bank?
Is the distance from the solar modules to batteries less than 50 feet (unless wire size is large enough to prevent voltage drop)?
Is the total solar array wattage less than ~450 watts?
Is the panel voltage (or array voltage) correct for the battery bank? (See table below.)