Many chargers simply disconnect the source from the batteries to stop the charging process, while others may short the source input leads together, thus diverting the power from going to the battery. Regulators of these types are usually used for solar power installations. Wind or hydropower generators, on the oter hand, usually require a diversion load type regulator.
Diversion load regulators connect an external load such as a heating element, lightbulbs, water pumping equipment, or other equipment to the batteries when they are fully charged. The load must consume at least as much power as the source can generate, otherwise the source may continue to overcharge the battery. When the battery voltage has dropped to within acceptable limits, the load will be disconnected from the battery, and charging will continue as before. Diversion load regulators can be used to control any type of power source within the rating of the regulator and diversion load. This type of regulator has the added advantage of utilizing what would otherwize be wasted power to heat water, power lights, pump water, or perform whatever other task (load) that the controller is connected to.
Most controllers are rated in amperage and voltage. The voltage rating indicates the battery voltage that the unit is appropriate for, while the amperage rating indicates the largest source that the controller can safely controll.