CTEK chargers have 2 conditioning charge states.
The first is the desulphation stage 1, its a pulse charge but is only used if the 12 volts open circuit voltage is below 10 volts when first connected to the charger. The idea behind this type of pulsing charge is to slowly bring the battery back up into normal charging conditions by slowly bringing the voltage up and not by overheating the battery or ramming large current into plates not wanting to operate outside normal conditions.
The second conditioning state is a mode selected by the users on the following models. MXS 5.0, MXS 10, PRO15, PRO25, and other professional series chargers. Mode 5 is added to the otherwise 7 stage charger to increase the voltage to 15.8v (on a 12 volt battery) and maintain a low absorption charge to ensure the battery cells are equalised and that every possible area of the plate is fully saturated with energy. Much like leaving a sponge in water to ensure it soaks up every last little piece of water it can.
Vehicle's electrical systems are designed to operate within industry standards which on 12 volt systems includes voltages up to 16 volts. In fact, we know of many vehicles that peak at over 17 volts but still use 12 volt batteries. In general anything above 2.45 volts per cell (14.7 volts) is a maximum charge rate but for short periods of time a higher voltage helps desulphate lead crystal build-up and can be very helpful to extend batteries usable life. It can also be the treatment that pushes a battery too far and it fails from drying out so the frequency of use should be managed.
Keep in mind a recondition charge is only performed once on a battery when the battery is stored for a long period of time as the stage is only initiated the once.