Perimeter SR-i500 Replacement Battery 9.6V 40mAh Ni-MH

Perimeter SR-i500 / SR-i900R Series — 9.6V Ni-MH Replacement Battery

This 9.6V Ni-MH cell replaces the backup battery in the Perimeter SR-i500, SR-i600, SR-i800, and SR-i900R intruder alarm systems. Capacity is 40mAh (0.38Wh), matching the original cell's footprint at 23.05 × 23.45 × 12.23 mm. It restores backup power so the panel continues to monitor and detect during mains failure.

• SR-i500 to SR-i900R platform fit: These four models share the same compact battery bay dimensions and 9.6V supply rail. The connector orientation and physical envelope are identical across the range, so one cell covers all four units without modification.
• Bench tested on actual hardware: We ran this cell through a full charge cycle on the SR-series panel and confirmed the BMS accepted the charge without fault flags. The panel cleared its low-battery warning after the float charge phase completed.
• Post-swap conditioning on SR-series panels: Do not run a zone or siren test immediately after fitting this cell. The SR-series panel measures battery state during the diagnostic routine, and a partially charged cell will trigger a low-battery fault during the test. Allow 24–48 hours on mains power before running any panel diagnostics.

Why the SR-i500 panel keeps reporting low battery after a new cell is fitted

The SR-series panel samples battery voltage at fixed intervals and compares it against a threshold — typically around 8.4V for a 9.6V Ni-MH pack. A new cell ships partially discharged, and its resting voltage can sit below that threshold for the first several hours on charge. The panel has no way to distinguish a new cell from a failing one until the float charge cycle completes. Leave the panel on mains for a full 48 hours after fitting the new cell, then check the display — the low-battery indicator should clear once voltage stabilises above the cutoff threshold.

Alarm losing programming during a power outage after battery replacement

If the panel loses its zone and user settings during a mains outage, the replacement cell has not yet been accepted into the backup circuit. The SR-series panel requires the battery to reach a minimum charge state before it hands over load during a mains drop. A cell installed less than 48 hours before an outage may not hold enough charge to sustain panel memory. Fit the cell, leave it on mains for 48 hours, then test with a brief mains interruption to confirm the panel holds its programming.