Impedance testing for UPS batteries is a non-intrusive way of preventing battery failure by identifying early signs of weakness or general deterioration in individual cells.
An AC current is applied to each battery through probes attached to the block terminals, with the internal impedance measured and recorded in milliohms. This broadly indicates the general condition the batteries are in, without placing any undue stress on their functionality.
Battery problems evolve over time and as they get older, their internal impedance increases until it reaches a manufacturer-defined threshold where replacement is recommended to reduce the likelihood of complete failure.
Regular impedance testing (i.e. every 6-to-12 months) enables you to build up an ongoing history of internal battery condition for every cell. Comparing batteries against each other makes it easier to accurately forecast end-of-working-life predictions and calculate when proactive replacement is necessary.
Impedance testing is non-intrusive, so can be undertaken in situ on a live working battery system and completed in a few hours. As a comparison, another type of battery testing called battery discharge testing often requires operations to be shut down for several days at a time while the test takes place, potentially exposing your critical load if there is an issue with the mains supply.
The main drawback of impedance testing is that it only gives a broad indication of the batteries' condition. For a more detailed analysis, more intrusive testing, such as load bank testing, is required.
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Lifespan of UPS batteries
Batteries are essential for UPS correct functioning. In this whitepaper we explain the main important factor that affect their duration and we provide some recommendations for optimizing the UPS + batteries system, in order to maximize its lifespan and general availability.
