Solar charge controllers are devices that are connected between a solar panel (link this to PV panels) or an array of solar panels and the battery bank or power grid. Solar charge controllers perform the critical function of controlling the voltage and current received at the battery to prevent overcharging and damaging the battery.

Types and Technologies

There are several different types of solar charge controllers. Each type differs in complexity, efficiency, and price.

Simple solar charge controllers -- Simple charge controllers use components, like relays, to  turn charge current on and off when specified charge voltages are reached. Since these controllers have few components to break, they are highly reliable.

Pulse Width Modulation (PWM) solar charge controllers -- PWM controllers are among the most used types. They are better than simple charge controllers because they more closely monitor the battery state between each pulse, allowing batteries to reach closer to maximum capacity and maintain more capacity using a trickle charge.

Maximum Power Point Tracking (MPPT) solar charge controllers -- MPPT controllers are the most advanced available.  High voltage solar panels require this type of controller. A MPPT controller uses a DC-DC converter to convert the high panel voltage into lower voltage/higher current for battery charging. MPPT controllers use microprocessors to monitor battery state and panel voltage. These controllers can continuously adjust the DC output to provide as close to maximum power as possible. This ensures the panel is operating at maximum efficiency under all conditions. 

Specifications

The following specifications for solar charge controllers are very important consider when selecting the right product for your situation.

Rated current -- This is the controller’s rated output current that it provides to charge batteries. Since current charges the batteries, too low a rated current causes the batteries to charge too slowly to be effective. Too high a rated current could damage battery internals.

Rated Voltage -- This is the rated voltages the controller can receive from the output of the solar panel system. A higher voltage rating could support multiple panels in series. This in turn eliminates the need for thick, expensive wiring to carry the current away from the solar system.

Features

Solar charge controllers can have many different features to enhance usability. Some of these features include:

Integral Display -- The controller will have a built in display that will inform operator of various parameters such input/output voltage and or current, and battery voltage and charge condition.

Datalogging -- The controller has built in datalogger to  record important parameters for review and storage at a later point.

Reverse Current Protection -- The controller prevents current from flowing from the battery back to the controller when panel voltage is lower than battery voltage. This is important during the nighttime, when no sun is hitting the panel.

Certifications

Solar charge controllers will often have one or more certifications. Following are the most common certifications.

CE Marking -- CE Marking indicates that a product complies with the essential requirements of relevant European Union (EU) directives that uphold national standards for health, safety and environmental protection. CE Marking is required in the countries of the European Economic Area (EEA), an organization that consists of the twenty five member states of the EU and the three members of the European Free Trade Association (EFTA). CE Marking refers to the safety of a product. It is not a quality standard.

UL Listing -- The UL Listing Mark indicates that Underwriters Laboratories Inc. (UL) has determined that representative samples of the product meet UL's safety requirements. These requirements are primarily based on UL's own published Standards for Safety. The UL Listing Mark is seen commonly on appliances and computer equipment, furnaces and heaters, fuses, electrical panelboards, smoke and carbon monoxide detectors, fire extinguishers and sprinkler systems, and thousands of other products.

TUV certification --TÜV Rheinland/Berlin-Brandenberg provides third-party product testing, system assessment, and certification services. TÜV Rheinland of North America is a member of the TÜV Rheinland Group and accredited by national organizations such as the American National Standards Institute (ANSI) and the Standards Council of Canada (SCC). Products that bear the TUVus Mark are certified for the U.S. market. Products that bear the cTUV Mark are certified for both the U.S. and Canadian markets.

C-UL Classification -- The C-UL Classification Mark from Underwriters Laboratories (UL) is applied to products intended for the Canadian marketplace. It indicates that UL has used Canadian standards to evaluate the product for specific hazards or properties.

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