Battery replacement that does not take the program with it, plus backup and recovery when one already has. Common battery part numbers for Allen-Bradley, Siemens, Omron, and Mitsubishi processors are stocked, so most jobs finish on the first visit.
A dead battery is a small job with a large risk attached, because the program can leave with it. Every PLC battery replacement is scheduled around securing the program first, so the panel is never opened without a verified copy in hand.
The program is read out and confirmed before the battery is removed, checked again once the new cell is in, and the backup file stays with you. Common parts include the 1747-BA and 1756-BA1 for SLC 500 and ControlLogix racks, 1769-BA for CompactLogix, and the battery packs behind MicroLogix 1000 through 1500. On Siemens processors we follow the siemens PLC backup procedure across S7-200 through S7-1500, and Omron, Mitsubishi FX2N, and GE Fanuc VersaMax processors get the same backup-first treatment. Where no backup exists, PLC backup software recovery is attempted before the battery is replaced blind.