IEEE has a detailed publication outlining their requirements for these subjects. We are outlining a much simpler approach without the dragged out details. Our discussion will be more of a discussion than a procedure. From this discussion, you can outline your own procedures to include all that you believe is best for your application. This does not, in any way, discount any recommendations by IEEE or other such entities in the service of UPS batteries.
Testing is a component of the maintenance.
Measuring the float voltage Measuring the open circuit voltage Measuring the AC voltage and current Measuring the internal impedance Applying a resistive load to the battery. Using a true RMS voltmeter, record the float voltage of each string directly at the main positive and negative battery terminals. When more than one string is connected in parallel, there is sometimes a means of disconnecting one string from the rest of the parallel strings. This may be with the use of a circuit breaker, switch, fuse, quick-disconnect connector, or by removing a cable from a main terminal. By measuring directly at the main terminals of each string, you will read the same voltage on each string unless a fuse is blown, a breaker is open, a switch is open, a connector is pulled apart, or if a main terminal cable is removed from one or more of the strings.