The lithium battery in the Allen-Bradley Programmable Logic Controllers (PLC) provides backup power to the processor’s memory. Should a power outage of less than 30 minutes long happen, the processor’s memory will use the battery’s backup power to retain information. The lithium battery will last between two to five years, depending on the type of processor and the amount the battery is used. A red “Battery Low” indicator on the front of the processor indicates when the battery voltage is getting low and the battery needs to be replaced. Writer Bio
