DC Power Supply Monitoring Sensors

UPS systems and generator start motors use standby lead acid batteries which degrade over time. Monitoring their temperature when charging or discharging can be used to indicate their overall health and ability to provide backup power. As lead acid batteries age, their internal resistance increase, leading to heat rise on discharge and a faster rate of discharge which can impact service life. Monitoring individual batteries and comparing readings taken over a time period can help to identify early failures which could lower the overall performance of the battery set.

For individual battery block monitoring, sensors are used that can be connected directly to battery terminals or lugs. Each battery within a battery string or battery set must have a sensor. Alterantively, a battery health monitoring system may use current transformers and sensors to provide an overall state-of-health and measurement data. The sensors connect to their base monitoring unit using local WiFi, gateway or hardwired RJ45 connection and the base unit issues notification alerts via email, SMS text and SNMP.

The most commonly installed UPS lead acid batteries have a 5year design life and should be replaced in years 3-4 of operation. This timeframe is dependent upon the ambient temperature they have been operated within which ideally should be between 20-25degC. 10year design life lead acid batteries are typically replaced in years 7-8 of operation. Whilst the batteries may still provide backup power to a UPS on mains power failure, their capacity to support this function reduces over time and can collapse rapidly for an aged battery set.