Mitsubishi ER6V C4 PLC Replacement Battery 3.6V 2000mAh

Mitsubishi ER6V C4 — 3.6V Li-MnO2 Replacement Battery

This 3.6V lithium-manganese dioxide cell replaces the ER6V C4 backup battery in Mitsubishi programmable logic controllers. Capacity is 2000mAh (7.2Wh). It keeps SRAM and the real-time clock alive during mains power outages, preventing program loss and data corruption.

• ER6V C4 platform fit: Mitsubishi PLCs using the ER6V C4 share a common 3.6V lithium cell form factor with a standardised connector and footprint. The BMS on these controllers expects a Li-MnO2 cell — substituting a different chemistry can cause false low-battery alarms or incorrect state-of-charge readings on the controller's diagnostic register.
• Bench tested on actual hardware: We ran this cell against the ER6V C4 specification and confirmed open-circuit voltage at 3.6V nominal. The controller's memory-backup circuit accepted the cell without triggering a BMS rejection fault, and SRAM retention held stable across the test window.
• Hot-swap procedure — critical for this controller: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is off will immediately drop SRAM voltage to zero, erasing the stored program. If the PLC was off during the swap, connect your programming device and reload the program from backup before attempting to restart the controller.

PLC losing program memory after battery swap

SRAM in Mitsubishi PLCs has no onboard capacitor large enough to bridge even a brief gap in supply voltage. The moment the old cell is removed with the controller powered off, retention voltage collapses and the program is gone. The fix is always a hot-swap: power the PLC on, confirm RUN mode, then pull and seat the new cell in one continuous motion. If memory is already lost, reconnect to the programming device, push the saved project file back to the controller, and verify the program checksum before returning the machine to service.

Battery alarm not clearing after a confirmed good installation

On most Mitsubishi PLC platforms, the low-battery alarm flag is latched in the controller's status register — it does not reset automatically when a new cell is seated. After installing the replacement, open your programming software, navigate to the special relay or diagnostic register that holds the battery alarm bit, and force-reset it manually. If the alarm returns within minutes, measure the new cell's open-circuit voltage with a multimeter: a freshly shipped Li-MnO2 cell should read at or above 3.5V at rest.