How often should UPS batteries be replace?

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.