What it is and what it backs up
The Mitsubishi FX3U-32BL is a 3 V lithium metal battery that sits inside the FX3U series PLC to retain program memory in built-in RAM, keep devices (battery-backed data registers and latched coils), sampling trace results, and the real-time clock when the main power is off.
Fit and compatibility
This is the OEM-specified backup battery for the Mitsubishi FX3U PLC family. It drops into the battery holder on the CPU module or memory cassette. No wiring or configuration — just a CR-type coin cell swap during powered-down maintenance. The 3 V nominal voltage matches the FX3U's memory retention circuit.
Compliance and handling note
Lithium metal construction means this battery falls under IATA/ICAO special provision A45 for air freight; 0.15 g lithium content per cell keeps it under most modal thresholds for small-quantity shipments. Dispose per local regulations for lithium metal cells — do not incinerate or short-circuit.