In standby mode The first step to checking the unit in standby mode is to turn the line breaker off. If it doesn't go into standby, turn on the line breaker and check the battery connections and internal wiring. Once in standby, use the same techniques that were used for the line source to check the amps that are delivered by the batteries. Next, use the voltmeter to test the battery string voltage and log it in the maintenance sheet. By keeping accurate records, it is possible to determine battery run time under various conditions with some degree of accuracy.
Many factors contribute to the life of batteries.
Heat, for example, is a major factor. The life of a battery is usually determined by assuming an environment of 77 degrees Fahrenheit. However, most power supply cabinets are exposed to extreme temperatures. In general, the rated life of a battery will decrease 50 percent for every 8 to 10 degrees above 77 degrees. Therefore, a battery with a 10-year life at 77 degrees will last only 18 to 24 months out in the field.