UPS battery symmetry monitoring

21 August 2020
CS141 provides symmetry monitoring for UPS systems with center tap

Many modern UPS systems use "center tap" for their batteries. The batteries are divided into two strings, one string provides the positive voltage and the 2nd provides the negative voltage.

When the batteries are all identical and in good condition, then the voltages do not differ, then the battery voltage of either polarity is identical. However, there might be a defective battery in one of the two strings which will cause a voltage difference. To recognize and generate a warning, some products monitor symmetry, but they are not very reliable. Symmetry checks have to be set the problem is it is either too "sensitive" and thus triggers false alarms or set too tolerant and does not recognize an error. Since these systems cannot be operated remotely via a network, for example, to set the sensitivity during operation, a BACS or CS141 system provides a natural advantage and the sensitivity can be configured significantly better for each situation.

Available on all CS141 for UPS where we read the measured values for the battery voltage for a center tap, we now offer a new configurable limit: "Battery Symmetry". This allows the configuration of a "symmetry monitoring" which outputs a warning when the batteries, for example, differ in the two strings by more than 3 volts. It can now be issued a warning and trigger the 2nd limit as an alarm escalation. Below is the configuration of the symmetry monitoring CS141 / BACS.

The user can utilize the CS141 to improve the performance of the UPS at no additional cost since no additional equipment needs to be installed for a separate "Symmetry monitoring". CS141 adds value in the use of such UPS types than the conventional SNMP cards from other manufacturers.

At UPS>Devices, click on Custom Thresholds and activate the string symmetry functions.