What is a solar charge controller’s function?

Any system with energy storage needs a way to regulate the flow of energy into the batteries. Philip Undercuffler, director of strategic platforms at OutBack Power, said that regulation prevents the batteries from overcharging and potentially receiving damage.

“Solar charge controllers regulate the energy flowing from the PV array and transfer it directly to the batteries as a DC-coupled system, which is the most efficient and effective manner,” he said. Giving batteries as long of a life as possible is an important function of a charge controller.

Two different types of charge controllers exist for solar systems. The first, which Undercuffler simply referred to as the “standard,” is usually small and commonly features pulse-width modulation (PWM). “The PWM controllers are old school and not very efficient,” said Bob Gudgel and Kim Silva of MidNite Solar. PWM technology sends out short controlling pulses to the batteries and is not particularly agile. It lacks the ability to optimize an entire array based on differences between panels, for example. PWM is adequate in places with constant, steady and strong solar radiation and in systems that are cost-sensitive, according to Undercuffler.

The second and most common type of controller has maximum power point tracking (MPPT) technology. These units are often found in larger systems and offer higher performance through their ability to extract all available power from the panels, Undercuffler explained. MPPT charge controllers increase a solar array’s effectiveness 30%, making it the preferred technology in all but the most basic systems. The MPPT controllers also connect strings of panels in a series for higher voltages, keeping amperage low and wire size smaller, especially for long wire runs to the PV array, said Gudgel and Silva.

Charge controllers have taken on several new features in the market lately, including increased capacity as they reach higher operating voltages to accommodate larger systems. Undercuffler also cited better flexibility, with more controllers using improved weather-resistant designs that operate under greater environmental extremes with less maintenance. “This is very important as charge controllers have often been the Achilles’ heel of PV systems and usually contain its only moving parts,” he said. Newer designs with superior thermal management will enable designers to bring solar to more demanding areas that require electricity, including research stations, remote telecommunications sites and mining and energy operations.

Energy storage is growing and advancing, causing charge controllers to become more prevalent. Charge controlling is a prerequisite to storing surplus electricity in batteries, according to Undercuffler. “With increasing diversity in battery technology—from the resurgence of ‘Edison’ iron types to lithium-ion, and aqueous to advanced lead-acid—the need for smarter, flexible and reliable charge controllers can only grow with the demand for clean electricity,” he said.

For more information, see:
How to choose the perfect charge controller