Tekcell SB-AA02 PLC Replacement Battery 3.6V 1200mAh

Tekcell SB-AA02 — 3.6V Li-SOCl2 Replacement Battery

This is a 3.6V, 1200mAh Li-SOCl2 cell replacing the Tekcell SB-AA02. It fits industrial PLCs and control systems that use this cell for SRAM memory retention and real-time clock backup. When the original cell depletes, the controller loses program memory and clock data the moment mains power drops.

• PLC backup cell compatibility: Controllers that spec the SB-AA02 share a 3.6V Li-SOCl2 voltage rail for low-current SRAM float charge. The cell dimensions — 27.00 × 16.50 × 14.80mm — match the original footprint, so the connector seats correctly without mechanical stress on the board header.
• Bench tested on actual hardware: We ran this cell at the rated 3.6V float load typical of PLC backup circuits. The BMS held stable voltage under the micro-amp draw that SRAM retention requires. No voltage sag or anomalous self-discharge during the test window.
• Hot-swap is mandatory on this platform: Never remove the SB-AA02 with the PLC powered off. The SRAM holding this controller's program has no capacitor buffer — power the controller to RUN mode first, then swap the cell. A cold swap wipes memory and forces a full program reload from the programming device.

PLC losing program memory after battery swap

Li-SOCl2 cells supply the only continuous voltage keeping SRAM alive when mains power is absent. Unlike some rechargeable backup circuits, there is no supercapacitor bridging the gap during a cell change. If the old cell is pulled while the PLC is de-energised, even briefly, SRAM content is gone. Always confirm the controller is powered and in RUN mode before touching the battery connector — this is the single step that prevents a memory loss event.

Battery alarm not clearing after a confirmed good installation

A new cell at storage voltage can read slightly below the controller's alarm threshold immediately after installation — typically 3.4–3.5V versus the 3.6V nominal. The PLC battery alarm flag is set in firmware and does not clear automatically when voltage recovers. Allow the cell one to two hours on the PLC's float circuit, then manually acknowledge and reset the alarm inside the programming software. If the flag persists after voltage confirms at 3.6V, navigate to the diagnostic or system block in your programming tool and force a status reset there.