The Steca PR solar charge controllers were launched in the year 2004 as the fifth generation of charge controller technology (up to 720 Wp). This high class state of the art product upgrades the Steca Solarix series by a customer designed LCD which shows the accurate state of charge (SOC) in percent and as battery gauge symbol. The heart of the controller is the integrated circuit called ATONIC®II, which contains the improved regulation software based on a self-learning algorithm. This allows the charge controller to learn on the fly, and adjust according to the input garnered from the batteries during operation.This charging regulator has basic functions for specifying the charging state(SOC), charging specification and deep discharge protection that are futher described in the owners manual. Additional functions that can be activated in the settings are night light function, auto-test, presetting and serial number query are also explained in the manual available for download. During operation, the regulator monitors various parameters (U; I) of the battery and from that calculates the battery’s charge level (SOC = state of charge). The charge level is the energy level still available in the battery. Modifications in the system, e.g. the battery’s aging process are automatically taken into consideration by the system’s continuous learning process.