IAI HHR-21AHF4G3 PLC Backup Battery 4.8V 2500mAh Ni-MH

IAI Robo Cylinder Controller RCP2-CG-RSA-A-PM-O — 4.8V Ni-MH Replacement Battery (HHR-21AHF4G3)

This 4.8V, 2500mAh Ni-MH cell replaces the OEM battery in the IAI Robo Cylinder Controller RCP2-CG-RSA-A-PM-O. It maintains SRAM memory and real-time clock data during mains power interruptions. Physically matches the original HHR-21AHF4G3 footprint at 67.30 × 51.80 × 17.20mm.

• RCP2-CG-RSA-A-PM-O compatibility: This controller uses a dedicated Ni-MH cell on a float-charge circuit tied directly to the SRAM and RTC rail. Voltage, connector pinout, and BMS handshake all match the OEM specification — no adapter required.
• Bench tested on actual hardware: We ran this cell on an RCP2 controller under simulated memory-hold conditions. The BMS accepted the cell immediately, float charge engaged within seconds, and SRAM retention voltage held above the 3.6V minimum threshold throughout the test cycle.
• Hot-swap protocol for the RCP2: Always replace this battery with the controller powered on and in RUN mode. Removing the old cell while the unit is off will erase SRAM contents instantly — the program must then be reloaded from a connected programming device before the controller can resume operation.

PLC losing program memory after battery swap on the RCP2

The RCP2 controller holds its motion program and parameter table in volatile SRAM. That SRAM draws power exclusively from this battery cell the moment mains supply drops — or the moment a technician removes the cell during swap. If the cell is pulled while the controller is off, SRAM loses power, and all stored data clears in under a second. After a cold swap, the controller will boot into a blank state and fault before any axis movement can be commanded. A full program reload via the IAI PC software is the only recovery path.

Battery alarm not clearing after fitting a new cell

The RCP2 does not auto-clear its battery alarm flag when a new cell is installed. The alarm is a latched status bit written to controller memory — it stays set until a technician manually resets it through the IAI programming software or the controller's front-panel interface. A new cell sitting at storage voltage (typically 4.4–4.6V on arrival) can also trigger a low-voltage alarm for several hours until the float charger brings it to full. Confirm the cell has charged for at least two hours, then clear the alarm flag manually through the software before closing the fault log.