Battery charging with SITOP power supplies

The SITOP PSU3800 12 V/20 A (Article No. 6EP3424-8UB00-0AY0), 24 V/17 A (Article No. 6EP3436-8UB99-0AY0) and SITOP PSU300B 24 V/30 A (Article No. 6EP1437-3BA20) power supplies are suitable for charging lead rechargeable batteries. In the case of a V/I characteristic set for parallel operation, the battery will be charged with a constant current until approximately 95% of the set SITOP output voltage has been achieved. The charging current is then continuously reduced from 1.2 x rated current at 95% of the set voltage to approximately 0 A or the self-discharge current of the battery at 100% of the set output voltage, that is, resistance characteristic in this range.

As reverse voltage protection and polarity reversal protection, we recommend that a diode suitable for at least 1.2 x rated current of the power supply with a blocking voltage of at least 40 V is connected in series with the "+" output (anode connected to "+" output of the SITOP PSU300B and cathode connected to positive pole of the battery).

The output voltage of the power supply must be set at no-load to the end-of-charge voltage plus the voltage drop at the diode. For an end-of-charge voltage of e.g. 27.0 V DC (usual at 20  °C to 30  °C battery temperature; specifications of the battery manufacturer must be observed!) and 0.8 V voltage drop at the diode, the power supply must be set to 27.8 V during no-load operation.

General note for using SITOP power supplies as a battery-charging unit

When using SITOP as a battery charging unit, VDE 0510 or relevant national regulations must be observed, and adequate ventilation of the battery location provided. SITOP power supplies are designed as rack-mounting units, and protection against electric shock should therefore be provided by installation in an appropriate housing.

The value recommended by the battery manufacturer must be set as the end-of-charge voltage (depending on the battery temperature). An ideal temperature for the lead-acid battery is between +20 °C to +30 °C and the recommended end-of-charge voltage in this case is usually about 27 V.