The battery symmetry monitor measures the voltage difference between the two halves of a cell string connected to a centre tap. A healthy string divides the voltage equally; a cell with reversed polarity, an internal short circuit or sulphation shifts the centre point and the relay reports it at the output before the battery loses the capacity needed in case of a supply failure. The response value and the delay are set with potentiometers, and LEDs indicate operation and contact position. The relay operates on the closed-circuit principle, so a break in the measuring wire also triggers the alarm.
DOLD intends it for emergency power supply batteries and lists the faults detected: polarity reversal of single cells, internal short circuits and sulphation. The version with a separate auxiliary voltage covers high-voltage strings; the version supplied from the battery handles low-voltage strings without an additional supply. Gold-plated contacts for low loads are available on request.
For railways we propose it for onboard and buffer batteries at rolling stock chargers and for standby batteries of substations and technical rooms - wherever a battery floats on a charger and its failure would show only when the mains fails.
Parameters (UH 9830.12, from the datasheet):
