Batteries and battery systems are the most important component of any UPS system. UPS batteries are the engine, or the power source, if the utility power fails or some type of power anomaly is experienced. Batteries are the most common failure/problem within any UPS system.
To support the UPS and provide the voltage required, the battery system usually requires several batteries in a continuous string. Typically this could be somewhere between 10 and 40 batteries. These batteries are configured in a string that can produce anywhere from 120 through 480 volts (nominal), depending on the amount of batteries in that string.
If one of the batteries should fail, the entire string could potentially be lost. This is why battery health and battery string redundancy is so important when maintaining and configuring any UPS system.