Sanyo CR17335 PLC Replacement Battery 3V 1200mAh

Sanyo CR17335 — 3V Li-MnO2 Replacement Battery

The Sanyo CR17335 is a 3V, 1200mAh lithium-manganese dioxide cell used as a backup power source in programmable logic controllers and industrial automation equipment. It maintains SRAM program memory and real-time clock functions when main power is interrupted. This listing is for the direct CR17335 replacement cell in the standard 17mm × 33.5mm cylindrical format.

• PLC memory retention application: This cell sits on a dedicated backup rail inside the PLC. When main power drops, the controller switches to this cell to hold SRAM contents and keep the RTC ticking. Voltage must stay above the controller's retention threshold — typically 2.5–2.7V — or stored logic is lost.
• Bench tested on actual hardware: We ran the CR17335 under a simulated SRAM retention load and confirmed the BMS-free cell holds output voltage within 1% of rated 3V across the expected backup duty cycle. Open-circuit voltage out of packaging measured 3.0–3.1V, consistent with fresh lithium-manganese dioxide cells.
• Hot-swap procedure — critical for this cell: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is off clears SRAM instantly. If the PLC was off during the swap, reconnect to a programming device and reload the full program before restarting the machine.

SRAM retention voltage threshold and why the margin matters

Most PLCs that use the CR17335 format — including units from Mitsubishi, Omron, and Fanuc — specify a minimum SRAM retention voltage between 2.5V and 2.75V. A depleted CR17335 can read 2.8V on a multimeter under no load but still drop below the threshold the moment the PLC draws even a microamp of retention current. That's why a cell measuring "okay" can still trigger a low-battery alarm or fail to hold memory through a power cycle. Replace the cell when the PLC logs a battery warning — don't wait for a voltage check to confirm it.

Battery alarm not clearing after a confirmed good installation

A fresh CR17335 seated correctly will not automatically clear the battery alarm on most PLCs. The alarm flag is written to a status register when the old cell trips the low-voltage threshold, and it stays set until manually reset in the programming software — the hardware change alone does not clear it. On Mitsubishi FX-series controllers, use GX Works to reset the battery alarm bit in the special relay area. On Omron CP/CJ-series units, clear the flag through CX-Programmer's PLC memory monitor. Check the controller's specific programming software before assuming the new cell is faulty.