Batery faillure - Powerware 9120 UPS System

Advanced Battery Management Technology Prevents Premature Failure and Significantly Extends Battery Service Life
Batteries are the most critical component in the reliability of any UPS, but they face three fundamental challenges: All Batteries Need Charging
But extended charging significantly shortens battery life. Most batteries are charged with a trickle-charging process (a constant voltage feeding a low current to the battery). This method dries the electrolyte and corrodes the plates, reducing potential life by up to 50%.
Batteries Take Time To Recharge
Users can’t wait. During prolonged power outages, the UPS batteries will discharge and not recharge until the power returns. When there is a subsequent power failure before the batteries recharge, the computer will not have full backup time. Overly rapid charging can cause premature battery failure, so the trick is to charge at the fastest rate that is safe for the battery.


All Batteries Will Eventually Fail
The question isn’t “Will it happen?” but “When will it happen?” Because UPS batteries are valve-regulated, sealed lead acid, there has previously been no practical way to provide the user with any meaningful advance notice that batteries need to be replaced. In the past, the only way to know when the batteries were dead was when the power failed and took your computer down with it. Until now, typical UPS batteries have required replacement every two to three years.
Our exclusive ABM technology solves these UPS battery problems. It significantly increases the life of UPS batteries (see Figure 1), provides the fastest safe recharge time, and provides reliable advanced notice when the batteries need replacement. By extending battery life and virtually eliminating this major cause of surprise load crashes, we are able to offer the industry’s longest and most inclusive warranties on all products that incorporate ABM. No other manufacturer can make this statement.
ABM technology is available on Powerware 5115, 5125, 9120, 9125, 9140, 9155, 9170+, 9355, and BladeUPS UPSs.

You can find a replacement at http://www.batteryinternational.com/ups-batteries.html