50Hz charger technology
50Hz chargers essentially comprise a conventional 50Hz transformer which transforms the mains voltage into the charging voltage, and a rectifier that converts the AC voltage from the transformer into DC voltage.
Since the mains voltage is transferred directly via the transformer, fluctuations in the mains voltage have a direct effect on the charging voltage.
The charging current responds in the opposite manner to the voltage in that when the voltage increases, the charging current drops.
The battery charger either does not switch off at all (W characteristic), or it only switches off after a specified interval (Wa characteristic). With these characteristics, there is no detection of the point at which the gassing voltage is reached. The risk of overcharging or undercharging is very high since the voltage is not regulated to the precise extent required. Fluctuations in the mains voltage have a particularly large influence on the progress of the charging curve.
Unregulated 50Hz battery chargers with a two-stage characteristic (generally known as WoWa chargers) differ from battery chargers with a single-stage characteristic (W or Wa) in that they switch over during the charging process.
The charging current and battery voltage initially increase rapidly. Following an interval with a large charging current, the capacity of the battery to accept charge drops, and the charging current is reduced accordingly. After a specific value has been reached, an electromagnetic switch (=contactor) comes into play and switches over to top-up charging. This phase is time-limited, and when it ends the charger automatically switches off and stops charging. This charger does not feature a separate conservation charging phase. Far better charging results can be achieved than with single-phase characteristics, since top-up charging is able to charge the battery closer to its full capacity.
In summary it can be said that unregulated chargers have a very simple design. It is possible to use additional components to regulate the charging curve, but this is done rarely if at all.