All about Solar Charge Controllers

All about Solar Charge Controllers

Wagan Tech7/ 7/18

Posted by: Justin G.

What is a solar charge controller?

A solar charge controller is a device that regulates the electrical current coming from the solar panel, monitors the battery’s voltage, and prevents overcharging of the battery. Charge controllers are rated based on their maximum input amperage. There are two general types of solar charge controllers: "PWM" and "MPPT".

What is the difference between PWM and MPPT Controllers?

A PWM or “Pulse-Width Modulation” controller is the most common and widely used controller type. MPPT or “Maximum Power Point Tracking” controllers are able to optimize the output of the solar panel and extract an additional 15-30% more power than a PWM controller. Although considerably more expensive, the increased efficiency and power collection is usually worth the price for large, permanent systems.

Do I need a charge controller?

For smaller solar panels used for charging portable electronics, solar controllers are not necessary (but a diode is usually in place to prevent reverse-charging). Generally, for any solar array larger than 5A, a solar charge controller will be needed.

What size solar charge controller do I need?

To determine what size controller you need, there is a simple formula. Take the total amount of watts in your array, then divide that number by your battery voltage to get amps. Add 25% to that number, and you’ll have the size charge controller that you need (always round answers up).
For example, you have 2 solar panels that are 120 watts each (2 x 120 =240 watts). Now divide that number by your battery voltage (12V is the most common) and you get 240/12=20 amps. Add 25% to that number (to allow for cold temperatures) and you have 20 + 25%= 25 amps. For this example, a 12V, 25A charge controller would be needed.

What size wire from the solar charge controller to the battery do I need?

To determine what size wire you need, look at the chart below. Find the size controller that you have (in (A)mps) and look at the corresponding wire gauge (AWG) listed. This chart takes in account the "worst case scenario" of a full-load solar panel in hot temperature conditions based on a 10-foot or less run.

Controller Amperage - Wire Gauge

10A - 14AWG

20A - 12AWG

30A - 10AWG

40A - 8AWG

60A - 6AWG

80A - 4AWG

100A - 2AWG

We’d be happy to answer any question that you have regarding our products or your set-up!

email us at or call 1.800.231.5806!


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