Once VRLA malfunctions, it will cause the entire battery string to fail.
No technology can guarantee that it will not suddenly fail, so regardless of the solution adopted, it is necessary to use battery technology with dual battery strings. Plan a reasonable battery replacement cycle. Under ideal conditions, the battery will fail within the expected time. When a unit fails, replace the entire battery string. Compared to old batteries, new batteries have different electrical characteristics, and mixing old and new batteries in a battery string can lead to more faults. There are exceptions to this rule: battery failures that occur within six months of the completion of the replacement operation.
Battery monitoring is also required. Many UPS systems come with battery monitors, but third-party monitoring may be more accurate. Some UPS battery monitors measure the internal resistance of the battery, while others apply very low voltage for testing and operation. A seller claims that battery monitoring can rebalance battery strings, so you can mix old and new batteries. However, according to the manufacturer, there is no monitor that can accurately predict any battery failure before it occurs.
The electrolyte in VRLA may dry up after a period of time, but battery failure is mainly caused by multiple charging and discharging cycles, unstable mains voltage, and overheating in abnormal environments, which can also be caused by overcharging. All of these will shorten the battery life of UPS and may cause battery rupture and leakage. Overcharging may also cause hydrogen emissions.
The warranty period of batteries is structured, so their value will rapidly decrease in the early years. For example, if a battery is advertised as “10 years” but expires after 3 years, the warranty value can easily drop to less than half.
An environment below 77 degrees Fahrenheit (25 degrees Celsius) can ensure the most stable operation of the battery. Many UPS systems are often located in the same room as servers, rather than separate battery rooms. Since ASHRAE has raised the recommended operating temperature for IT equipment, the inlet air can now exceed 77 degrees Fahrenheit, while the daily discharge of hot air may be above 100 degrees Fahrenheit (38 degrees Celsius). Before introducing UPS into the data center, this point needs to be considered. Tests have shown that increasing the battery temperature by 15 degrees Fahrenheit (8.3 degrees Celsius) can reduce the lifespan of UPS batteries by 50%.
The battery generates heat during charging and discharging, so it is necessary to cool the battery as soon as possible after power outage recovery. Without a backup generator to support the refrigeration system, continuous deep discharge of the battery and temperature rise can significantly reduce battery life.
There is no reason to overcharge UPS batteries. A good charger has temperature monitoring and corrects for rising temperatures by reducing the charging current. Even with good maintenance, the VRLAUPS battery life should not be expected based on theoretical values, especially under unfavorable conditions. Any type of battery monitoring is far better than not monitoring at all.